Why is C so fast and why aren t other languages as fast or faster

Question

In listening to the StackOverflow podcast  the jab keeps coming up that  real programmers  write in C  and that C is so much faster because it s  close to the machine   Leaving the former assertion for another post  what is special about C that allows it to be faster than other languages  Or put another way  what s to stop other languages from being able to compile down to binary that runs every bit as fast as C

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Just step through the machine code in your IDE, and you'll see why it's faster (if it's faster). It leaves out a lot of hand-holding. Chances are your Cxx can also be told to leave it out too, in which case it should be about the same.

Compiler optimizations are overrated, as are almost all perceptions about language speed.

Optimization of generated code only makes a difference in hotspot code, that is, tight algorithms devoid of function calls (explicit or implicit). Anywhere else, it achieves very little.

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I know plenty of people have said it in a long winded way  but      C is faster because it does less  for you

User · Answer

Just step through the machine code in your IDE, and you'll see why it's faster (if it's faster). It leaves out a lot of hand-holding. Chances are your Cxx can also be told to leave it out too, in which case it should be about the same.

Compiler optimizations are overrated, as are almost all perceptions about language speed.

Optimization of generated code only makes a difference in hotspot code, that is, tight algorithms devoid of function calls (explicit or implicit). Anywhere else, it achieves very little.

User · Answer

Actually  in certain applications  numerics  even C can be beaten  and I don t mean assembly language  but the old  oft-ridiculed Fortran  The reason is  Fortran guarantees no pointer aliasing

User · Answer

Just step through the machine code in your IDE, and you'll see why it's faster (if it's faster). It leaves out a lot of hand-holding. Chances are your Cxx can also be told to leave it out too, in which case it should be about the same.

Compiler optimizations are overrated, as are almost all perceptions about language speed.

Optimization of generated code only makes a difference in hotspot code, that is, tight algorithms devoid of function calls (explicit or implicit). Anywhere else, it achieves very little.

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Setting aside advanced optimization techniques such as hot-spot optimization  pre-compiled meta-algorithms  and various forms of parallelism  the fundamental speed of a language correlates strongly with the implicit behind-the-scenes complexity required to support the operations that would commonly be specified within inner loops   Perhaps the most obvious is validity checking on indirect memory references -- such as checking pointers for null and checking indexes against array boundaries   Most high-level languages perform these checks implicitly  but C does not   However  this is not necessarily a fundamental limitation of these other languages -- a sufficiently clever compiler may be capable of removing these checks from the inner loops of an algorithm through some form of loop-invariant code motion   The more fundamental advantage of C  and to a similar extent the closely related C    is a heavy reliance on stack-based memory allocation  which is inherently fast for allocation  deallocation  and access   In C  and C    the primary call stack can be used for allocation of primitives  arrays  and aggregates  struct class      While C does offer the capability to dynamically allocate memory of arbitrary size and lifetime  using the so called  heap    doing so is avoided by default  the stack is used instead    Tantalizingly  it is sometimes possible to replicate the C memory allocation strategy within the runtime environments of other programming languages   This has been demonstrated by asm js  which allows code written in C or C   to be translated into a subset of JavaScript and run safely in a web browser environment -- with near-native speed     As somewhat of an aside  another area where C and C   outshine most other languages for speed is the ability to seamlessly integrate with native machine instruction sets   A notable example of this is the  compiler and platform dependent  availability of SIMD intrinsics which support the construction of custom algorithms that take advantage of the now nearly ubiquitous parallel processing hardware -- while still utilizing the data allocation abstractions provided by the language  lower-level register allocation is managed by the compiler

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Some C   algorithms are faster than C  and some implementations of algorithms or design patterns in other languages can be faster than C   When people say that C is fast  and then move on to talking about some other language  they are generally using C s performance as a benchmark

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I know plenty of people have said it in a long winded way  but      C is faster because it does less  for you

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It s the difference between automatic and manual  higher level languages are abstractions thus automated  C C   are manually controlled and handled  even error checking code is sometimes a manual labor   C and C   are also compiled languages which means none of that run everywhere business  these languages have to be fine tuned for the hardware you work with thus adding an extra layer of gotcha  Though this is slightly fazing out now as C C   compilers are becoming more common across all platforms  You can do cross compilations between platforms  It s still not a run everywhere situation  your basically instructing compiler A to compile against compiler B same code different architecture   Bottom line C languages are not meant to be easy to understand or reason  this is also why their referred to as systems languages  They came out before all this high level abstraction nonsense  This is also why they are not used for front end web programming  Their just not suited to the task  their mean to solve complex problems that can t be resolved with conventional language tooling   This is why you get crazy stuff like  micro-architectures  drivers  quantum physics  AAA Games  operating systems  there are things C and C   are just well suited for  Speed and number crunching being the chief areas

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1  As others have said  C does less for you  No initializing variables  no array bounds checking  no memory management  etc  Those features in other languages cost memory and CPU cycles that C doesn t spend   2  Answers saying that C is less abstracted and therefore faster are only half correct I think  Technically speaking  if you had a  sufficiently advanced compiler  for language X  then language X could approach or equal the speed of C  The difference with C is that since it maps so obviously  if you ve taken an architecture course  and directly to assembly language that even a naive compiler can do a decent job  For something like Python  you need a very advanced compiler to predict the probable types of objects and generate machine code on the fly -- C s semantics are simple enough that a simple compiler can do well

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Even the difference between C and C   can at times be great   When you are allocating memory for an object  invoking constructors  aligning memory on word boundaries  etc  the program winds up going through a lot of overhead that is abstracted away from the programmer   C forces you to take a look at each thing that your program is doing  generally at a very fine level of detail   This makes it harder  although not by any means impossible  to write code that does a lot of tasks that are unnecessary to the immediate goal at hand   So where in  for instance a BASIC program you would use the INPUT keyword to read a string form STDIN and automatically allocate memory for its variable  in C the programmer will typically have already allocated memory and can control things like whether the program blocks for I O or not  and if it stops reading input after it has the information it needs or continues reading characters to the end of the line   C also performs a lot less error-checking than other languages  presuming the programmer knows what they re doing   So whereas in PHP if you declare a string  myStr   getInput    and go on to reference  myStr 20   but the input was only 10 characters long  PHP will catch this and safely return to you a blank string   C assumes that you ve either allocated enough memory to hold data past the end of the string or that you know what information comes after the string and are trying to reference that instead   These small factors have a huge impact on overhead in aggregate

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For the most part  every C instruction corresponds to a very few assembler instructions   You are essentially writing higher level machine code  so you have control over almost everything the processor does   Many other compiled languages  such as C    have a lot of simple looking instructions that can turn into much more code than you think it does  virtual functions  copy constructors  etc     And interpreted languages like Java or Ruby have another layer of instructions that you never see - the Virtual Machine or Interpreter

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Don t take someones word for it  look at the dissassembly for both C and your language-of-choice in any performance critical part of your code   I think you can just look in the disassembly window at runtime in Visual Studio to see disassembled  Net  Should be possible if tricky for Java using windbg  though if you do it with  Net many of the issues would be the same   I don t like to write in C if I don t need to  but I think many of the claims made in these answers that tout the speed of languages other than C can be put aside by simply disassembling the same routine in C and in your higher level language of choice  especially if lots of data is involved as is common in performance critical applications  Fortran may be an exception in its area of expertise  don t know  Is it higher level than C   First time I did compared JITed code with native code resolved any and all questions whether  Net code could run comparably to C code  The extra level of abstraction and all the safety checks come with a significant cost  Same costs would probably apply to Java  but don t take my word for it  try it on something where performance is critical   Anyone know enough about JITed Java to locate a compiled procedure in memory  It should certainly be possible

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With modern optimizing compilers  it s highly unlikely that a pure C program is going to be all that much faster than compiled  net code  if at all  With the productivity enhancement that frameworks like  net provide the developer  you can do things in a day that used to take weeks or months in regular C  Coupled with the cheap cost of hardware compared to a developer s salary  it s just WAY cheaper to write the stuff in a high-level language and throw hardware at any slowness   The reason Jeff and Joel talk about C being the  real programmer  language is because there is no hand-holding in C  You must allocate your own memory  deallocate that memory  do your own bounds-checking  etc  There s no such thing as new object    There s no garbage collection  classes  OOP  entity frameworks  LINQ  properties  attributes  fields  or anything like that  You have to know things like pointer arithmetic and how to dereference a pointer  And  for that matter  know and understand what a pointer is  You have to know what a stack frame is and what the instruction pointer is  You  have to know the memory model of the CPU architecture you re working on  There is a lot of implicit understanding of the architecture of a microcomputer  usually the microcomputer you re working on  when programming in C that simply is not present nor necessary when programming in something like C  or Java  All of that information has been off-loaded to the compiler  or VM  programmer

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It s not so much about the language as the tools and libraries   The available libraries and compilers for C are much older than for newer languages   You might think this would make them slower  but au contraire   These libraries were written at a time when processing power and memory were at a premium   They had to be written very efficiently in order to work at all   Developers of C compilers have also had a long time to work in all sorts of clever optimizations for different processors   C s maturity and wide adoption makes for a signficant advantage over other languages of the same age   It also gives C a speed advantage over newer tools that don t emphasize raw performance as much as C had to

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This is actually a bit of a perpetuated falsehood   While it is true that C programs are frequently faster  this is not always the case  especially if the C programmer isn t very good at it   One big glaring hole that people tend to forget about is when the program has to block for some sort of IO  such as user input in any GUI program   In these cases  it doesn t really matter what language you use since you are limited by the rate at which data can come in rather than how fast you can process it   In this case  it doesn t matter much if you are using C  Java  C  or even Perl  you just cannot go any faster than the data can come in   The other major thing is that using garbage collection and not using proper pointers allows the virtual machine to make a number of optimizations not available in other languages   For instance  the JVM is capable of moving objects around on the heap to defragment it   This makes future allocations much faster since the next index can simply be used rather than looking it up in a table   Modern JVMs also don t have to actually deallocate memory  instead  they just move the live objects around when they GC and the spent memory from the dead objects is recovered essentially for free   This also brings up an interesting point about C and even more so in C     There is something of a design philosophy of  If you don t need it  you don t pay for it    The problem is that if you do want it  you end up paying through the nose for it   For instance  the vtable implementation in Java tends to be a lot better than C   implementations  so virtual function calls are a lot faster   On the other hand  you have no choice but to use virtual functions in Java and they still cost something  but in programs that use a lot of virtual functions  the reduced cost adds up

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Actually  in certain applications  numerics  even C can be beaten  and I don t mean assembly language  but the old  oft-ridiculed Fortran  The reason is  Fortran guarantees no pointer aliasing

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This is actually a bit of a perpetuated falsehood   While it is true that C programs are frequently faster  this is not always the case  especially if the C programmer isn t very good at it   One big glaring hole that people tend to forget about is when the program has to block for some sort of IO  such as user input in any GUI program   In these cases  it doesn t really matter what language you use since you are limited by the rate at which data can come in rather than how fast you can process it   In this case  it doesn t matter much if you are using C  Java  C  or even Perl  you just cannot go any faster than the data can come in   The other major thing is that using garbage collection and not using proper pointers allows the virtual machine to make a number of optimizations not available in other languages   For instance  the JVM is capable of moving objects around on the heap to defragment it   This makes future allocations much faster since the next index can simply be used rather than looking it up in a table   Modern JVMs also don t have to actually deallocate memory  instead  they just move the live objects around when they GC and the spent memory from the dead objects is recovered essentially for free   This also brings up an interesting point about C and even more so in C     There is something of a design philosophy of  If you don t need it  you don t pay for it    The problem is that if you do want it  you end up paying through the nose for it   For instance  the vtable implementation in Java tends to be a lot better than C   implementations  so virtual function calls are a lot faster   On the other hand  you have no choice but to use virtual functions in Java and they still cost something  but in programs that use a lot of virtual functions  the reduced cost adds up

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There are a lot of questions in there - mostly ones I am not qualified to answer  But for this last one       what s to stop other languages from being able to compile down to binary that runs every bit as fast as C    In a word  Abstraction    C is only one or 2 levels of abstraction away from machine language  Java and the  Net languages are at a minimum 3 levels of abstraction away from assembler  I m not sure about Python and Ruby    Typically  the more programmer toys  complex data types  etc    the further you are from machine language and the more translation has to be done    I m off here and there but that s the basic gist   Update ------- There are some good comments on this post with more details

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It s not so much about the language as the tools and libraries   The available libraries and compilers for C are much older than for newer languages   You might think this would make them slower  but au contraire   These libraries were written at a time when processing power and memory were at a premium   They had to be written very efficiently in order to work at all   Developers of C compilers have also had a long time to work in all sorts of clever optimizations for different processors   C s maturity and wide adoption makes for a signficant advantage over other languages of the same age   It also gives C a speed advantage over newer tools that don t emphasize raw performance as much as C had to

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Even the difference between C and C   can at times be great   When you are allocating memory for an object  invoking constructors  aligning memory on word boundaries  etc  the program winds up going through a lot of overhead that is abstracted away from the programmer   C forces you to take a look at each thing that your program is doing  generally at a very fine level of detail   This makes it harder  although not by any means impossible  to write code that does a lot of tasks that are unnecessary to the immediate goal at hand   So where in  for instance a BASIC program you would use the INPUT keyword to read a string form STDIN and automatically allocate memory for its variable  in C the programmer will typically have already allocated memory and can control things like whether the program blocks for I O or not  and if it stops reading input after it has the information it needs or continues reading characters to the end of the line   C also performs a lot less error-checking than other languages  presuming the programmer knows what they re doing   So whereas in PHP if you declare a string  myStr   getInput    and go on to reference  myStr 20   but the input was only 10 characters long  PHP will catch this and safely return to you a blank string   C assumes that you ve either allocated enough memory to hold data past the end of the string or that you know what information comes after the string and are trying to reference that instead   These small factors have a huge impact on overhead in aggregate

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There are a many reasons  including   It compiles into assembly language  It is statically typed  No garbage collection  No exception mechanism  Compiler optimizations Part of the philosophy of C is to keep things simple and maintain backwards compatibility  instead of adding more features

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The lack of abstraction is what makes C faster  If you write an output statement you know exactly what is happening  If you write an output statement in java it is getting compiled to a class file which then gets run on a virtual machine introducing a layor of abstraction  The lack of object oriented features as a part of the language also increases it s speed do to less code being generated  If you use C as an object oriented language then you are doing all the coding for things such as classes  inharitence  etc  This means rather then make something generalized enough for everyone with the amount of code and the performance penelty that requires you only write what you need to get the job done

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C is not always faster   C is slower than  for example Modern Fortran   C is often slower than Java for some things    Especially after the JIT compiler has had a go at your code   C lets pointer aliasing happen  which means some good optimizations are not possible  Particularly when you have multiple execution units  this causes data fetch stalls  Ow   The assumption that pointer arithmetic works really causes slow bloated performance on some CPU families  PIC particularly   It used to suck the big one on segmented x86   Basically  when you get a vector unit  or a parallelizing compiler  C stinks and modern Fortran runs faster   C programmer tricks like thunking   modifying the executable on the fly  cause CPU prefetch stalls   You get the drift    And our good friend  the x86  executes an instruction set that these days bears little relationship to the actual CPU architecture   Shadow registers  load-store optimizers  all in the CPU  So C is then close to the virtual metal  The real metal  Intel don t let you see   Historically VLIW CPU s were a bit of a bust so  maybe that s no so bad    If you program in C on a high-performance DSP  maybe a TI DSP     the compiler has to do some tricky stuff to unroll the C across the multiple parallel execution units  So in that case C isn t close to the metal  but it is close to the compiler  which will do whole program optimization  Weird   And finally  some CPUs  www ajile com  run Java bytecodes in hardware  C would a PITA to use on that CPU

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It s the difference between automatic and manual  higher level languages are abstractions thus automated  C C   are manually controlled and handled  even error checking code is sometimes a manual labor   C and C   are also compiled languages which means none of that run everywhere business  these languages have to be fine tuned for the hardware you work with thus adding an extra layer of gotcha  Though this is slightly fazing out now as C C   compilers are becoming more common across all platforms  You can do cross compilations between platforms  It s still not a run everywhere situation  your basically instructing compiler A to compile against compiler B same code different architecture   Bottom line C languages are not meant to be easy to understand or reason  this is also why their referred to as systems languages  They came out before all this high level abstraction nonsense  This is also why they are not used for front end web programming  Their just not suited to the task  their mean to solve complex problems that can t be resolved with conventional language tooling   This is why you get crazy stuff like  micro-architectures  drivers  quantum physics  AAA Games  operating systems  there are things C and C   are just well suited for  Speed and number crunching being the chief areas

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It s all about time and effort   Given an infinite amount of time and effort    An assembly program will be faster than one written in C  A C program will be faster than one written in C      Given an fixed amount of time and effort    A C   program will be faster than one written in C  A C program will be faster than one written in Assembly    Why  Because the more abstraction you do  the more time you can spend optimising the critical sections of code that really matter  A couple of assumptions here is a developer is equally competent in all three languages  you don t care about binary size  memory usage  etc   Every abstraction has a cost performance-wise but should make code easier and faster to write

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For the most part  every C instruction corresponds to a very few assembler instructions   You are essentially writing higher level machine code  so you have control over almost everything the processor does   Many other compiled languages  such as C    have a lot of simple looking instructions that can turn into much more code than you think it does  virtual functions  copy constructors  etc     And interpreted languages like Java or Ruby have another layer of instructions that you never see - the Virtual Machine or Interpreter

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Amazing to see the old  C C   must be faster than Java because Java is interpreted  myth is still alive and kicking  There are articles going back a few years  as well as more recent ones  that explain with concepts or measurements why this simply isn t always the case   Current virtual machine implementations  and not just the JVM  by the way  can take advantage of information gathered during program execution to dynamically tune the code as it runs  using a variety of techniques    rendering frequent methods to machine code  inlining small methods  adjustment of locking   and a variety of other adjustments based on knowing what the code is actually doing  and on the actual characteristics of the environment in which it s running

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what s to stop other languages from   being able to compile down to binary   that runs every bit as fast as C    Nothing  Modern languages like Java or  NET langs are oriented more on programmer productivity rather than performance  Hardware is cheap now days  Also compilation to intermediate representation gives a lot of bonuses such as security  portability etc   NET CLR can take advantage of different hardware - for example you don t need to manually optimize recompile program to use SSE instructions set

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The main factors are that it s a statically-typed language and that s compiled to machine code  Also  since it s a low-level language  it generally doesn t do anything you don t tell it to   These are some other factors that come to mind    Variables are not automatically initialized No bounds checking on arrays Unchecked pointer manipulation No integer overflow checking Statically-typed variables Function calls are static  unless you use function pointers  Compiler writers have had lots of time to improve the optimizing code  Also  people program in C for the purpose of getting the best performance  so there s pressure to optimize the code  Parts of the language specification are implementation-defined  so compilers are free to do things in the most optimal way   Most static-typed languages could be compiled just as fast or faster than C though  especially if they can make assumptions that C can t because of pointer aliasing  etc

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Some C   algorithms are faster than C  and some implementations of algorithms or design patterns in other languages can be faster than C   When people say that C is fast  and then move on to talking about some other language  they are generally using C s performance as a benchmark

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Don t take someones word for it  look at the dissassembly for both C and your language-of-choice in any performance critical part of your code   I think you can just look in the disassembly window at runtime in Visual Studio to see disassembled  Net  Should be possible if tricky for Java using windbg  though if you do it with  Net many of the issues would be the same   I don t like to write in C if I don t need to  but I think many of the claims made in these answers that tout the speed of languages other than C can be put aside by simply disassembling the same routine in C and in your higher level language of choice  especially if lots of data is involved as is common in performance critical applications  Fortran may be an exception in its area of expertise  don t know  Is it higher level than C   First time I did compared JITed code with native code resolved any and all questions whether  Net code could run comparably to C code  The extra level of abstraction and all the safety checks come with a significant cost  Same costs would probably apply to Java  but don t take my word for it  try it on something where performance is critical   Anyone know enough about JITed Java to locate a compiled procedure in memory  It should certainly be possible

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C is not always faster   C is slower than  for example Modern Fortran   C is often slower than Java for some things    Especially after the JIT compiler has had a go at your code   C lets pointer aliasing happen  which means some good optimizations are not possible  Particularly when you have multiple execution units  this causes data fetch stalls  Ow   The assumption that pointer arithmetic works really causes slow bloated performance on some CPU families  PIC particularly   It used to suck the big one on segmented x86   Basically  when you get a vector unit  or a parallelizing compiler  C stinks and modern Fortran runs faster   C programmer tricks like thunking   modifying the executable on the fly  cause CPU prefetch stalls   You get the drift    And our good friend  the x86  executes an instruction set that these days bears little relationship to the actual CPU architecture   Shadow registers  load-store optimizers  all in the CPU  So C is then close to the virtual metal  The real metal  Intel don t let you see   Historically VLIW CPU s were a bit of a bust so  maybe that s no so bad    If you program in C on a high-performance DSP  maybe a TI DSP     the compiler has to do some tricky stuff to unroll the C across the multiple parallel execution units  So in that case C isn t close to the metal  but it is close to the compiler  which will do whole program optimization  Weird   And finally  some CPUs  www ajile com  run Java bytecodes in hardware  C would a PITA to use on that CPU

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This is actually a bit of a perpetuated falsehood   While it is true that C programs are frequently faster  this is not always the case  especially if the C programmer isn t very good at it   One big glaring hole that people tend to forget about is when the program has to block for some sort of IO  such as user input in any GUI program   In these cases  it doesn t really matter what language you use since you are limited by the rate at which data can come in rather than how fast you can process it   In this case  it doesn t matter much if you are using C  Java  C  or even Perl  you just cannot go any faster than the data can come in   The other major thing is that using garbage collection and not using proper pointers allows the virtual machine to make a number of optimizations not available in other languages   For instance  the JVM is capable of moving objects around on the heap to defragment it   This makes future allocations much faster since the next index can simply be used rather than looking it up in a table   Modern JVMs also don t have to actually deallocate memory  instead  they just move the live objects around when they GC and the spent memory from the dead objects is recovered essentially for free   This also brings up an interesting point about C and even more so in C     There is something of a design philosophy of  If you don t need it  you don t pay for it    The problem is that if you do want it  you end up paying through the nose for it   For instance  the vtable implementation in Java tends to be a lot better than C   implementations  so virtual function calls are a lot faster   On the other hand  you have no choice but to use virtual functions in Java and they still cost something  but in programs that use a lot of virtual functions  the reduced cost adds up

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There isn t much that s special about C  That s one of the reasons why it s fast   Newer languages which have support for garbage collection  dynamic typing and other facilities which make it easier for the programmer to write programs    The catch is  there is additional processing overhead which will degrade the performance of the application  C doesn t have any of that  which means that there is no overhead  but that means that the programmer needs to be able to allocate memory and free them to prevent memory leaks  and must deal with static typing of variables   That said  many languages and platforms  such as Java  with its Java Virtual Machine  and  NET  with its Common Language Runtime  have improved performance over the years with advents such as just-in-time compilation which produces native machine code from bytecode to achieve higher performance

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For the most part  every C instruction corresponds to a very few assembler instructions   You are essentially writing higher level machine code  so you have control over almost everything the processor does   Many other compiled languages  such as C    have a lot of simple looking instructions that can turn into much more code than you think it does  virtual functions  copy constructors  etc     And interpreted languages like Java or Ruby have another layer of instructions that you never see - the Virtual Machine or Interpreter

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There is a trade off the C designers have made  That s to say  they made the decision to put speed above safety  C won t  Check array index bounds Check for uninitialized variable values Check for memory leaks Check for null pointer dereference  When you index into an array  in Java it takes some method call in the virtual machine  bound checking and other sanity checks  That is valid and absolutely fine  because it adds safety where it s due  But in C  even pretty trivial things are not put in safety  For example  C doesn t require memcpy to check whether the regions to copy overlap  It s not designed as a language to program a big business application  But these design decisions are not bugs in the C language  They are by design  as it allows compilers and library writers to get every bit of performance out of the computer  Here is the spirit of C how the C Rationale document explains it   C code can be non-portable  Although it strove to give programmers the opportunity to write truly portable programs  the Committee did not want to force programmers into writing portably  to preclude the use of C as a   high-level assembler    the ability to write machine-specific code is one of the strengths of C  Keep the spirit of C  The Committee kept as a major goal to preserve the traditional spirit of C   There are many facets of the spirit of C  but the essence is a community sentiment of the underlying principles upon which the C language is based   Some of the facets of the spirit of C can be summarized in phrases like  Trust the programmer  Don t prevent the programmer from doing what needs to be done  Keep the language small and simple  Provide only one way to do an operation  Make it fast  even if it is not guaranteed to be portable   The last proverb needs a little explanation   The potential for efficient code generation is one of the most important strengths of C   To help ensure that no code explosion occurs for what appears to be a very simple operation  many operations are defined to be how the target machine s hardware does it rather than by a general abstract rule   An example of this willingness to live with what the machine does can be seen in the rules that govern the widening of char objects for use in expressions  whether the values of char objects widen to signed or unsigned quantities typically depends on which byte operation is more efficient on the target machine

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The main factors are that it s a statically-typed language and that s compiled to machine code  Also  since it s a low-level language  it generally doesn t do anything you don t tell it to   These are some other factors that come to mind    Variables are not automatically initialized No bounds checking on arrays Unchecked pointer manipulation No integer overflow checking Statically-typed variables Function calls are static  unless you use function pointers  Compiler writers have had lots of time to improve the optimizing code  Also  people program in C for the purpose of getting the best performance  so there s pressure to optimize the code  Parts of the language specification are implementation-defined  so compilers are free to do things in the most optimal way   Most static-typed languages could be compiled just as fast or faster than C though  especially if they can make assumptions that C can t because of pointer aliasing  etc

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If you spend a month to build something in C that runs in 0 05 seconds  and I spend a day writing the same thing in Java  and it runs in 0 10 seconds  then is C really faster   But to answer your question  well-written C code will generally run faster than well-written code in other languages because part of writing C code  well  includes doing manual optimizations at a near-machine level   Although compilers are very clever indeed  they are not yet able to creatively come up with code that competes with hand-massaged algorithms  assuming the  hands  belong to a good C programmer    Edit   A lot of comments are along the lines of  I write in C and I don t think about optimizations    But to take a specific example from this post   In Delphi I could write this   function RemoveAllAFromB a  b  string   string  var   before  after  string  begin   Result    b    if 0  lt  Pos a b  then begin     before    Copy b 1 Pos a b -Length a        after    Copy b Pos a b  Length a  Length b        Result    before   after      Result    RemoveAllAFromB a Result      recursive   end  end    and in C I write this   char  s1   s2   result     original strings and the result string    int len1  len2     lengths of the strings    for  i   0  i  lt  len1  i         for  j   0  j  lt  len2  j           if  s1 i     s2 j            break                 if  j    len2        s1 i  is not found in s2          result   s1 i         result       assuming your result array is long enough             But how many optimizations are there in the C version   We make lots of decisions about implementation that I don t think about in the Delphi version   How is a string implemented   In Delphi I don t see it   In C  I ve decided it will be a pointer to an array of ASCII integers  which we call chars   In C  we test for character existence one at a time   In Delphi  I use Pos   And this is just a small example   In a large program  a C programmer has to make these kinds of low-level decisions with every few lines of code   It adds up to a hand-crafted  hand-optimized executable

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C is not always faster   C is slower than  for example Modern Fortran   C is often slower than Java for some things    Especially after the JIT compiler has had a go at your code   C lets pointer aliasing happen  which means some good optimizations are not possible  Particularly when you have multiple execution units  this causes data fetch stalls  Ow   The assumption that pointer arithmetic works really causes slow bloated performance on some CPU families  PIC particularly   It used to suck the big one on segmented x86   Basically  when you get a vector unit  or a parallelizing compiler  C stinks and modern Fortran runs faster   C programmer tricks like thunking   modifying the executable on the fly  cause CPU prefetch stalls   You get the drift    And our good friend  the x86  executes an instruction set that these days bears little relationship to the actual CPU architecture   Shadow registers  load-store optimizers  all in the CPU  So C is then close to the virtual metal  The real metal  Intel don t let you see   Historically VLIW CPU s were a bit of a bust so  maybe that s no so bad    If you program in C on a high-performance DSP  maybe a TI DSP     the compiler has to do some tricky stuff to unroll the C across the multiple parallel execution units  So in that case C isn t close to the metal  but it is close to the compiler  which will do whole program optimization  Weird   And finally  some CPUs  www ajile com  run Java bytecodes in hardware  C would a PITA to use on that CPU

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The fastest running code would be carefully hand crafted machine code  Assembler will be almost as good  Both are very low level and it takes a lot of writing code to do things  C is a little above assembler  You still have the ability to control things at a very low level in the actual machine  but there is enough abstraction make writing it faster and easier then assembler  Other languages such as C  and JAVA are even more abstract  While Assembler and machine code are called low level languages  C  and JAVA  and many others  are called high level languages  C is sometimes called a middle level language

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I guess you forgot that Assembly language is also a language     But seriously  C programs are faster only when the programmer knows what he s doing  You can easily write a C program that runs slower than programs written in other languages that do the same job   The reason why C is faster is because it is designed in this way  It lets you do a lot of  lower level  stuff that helps the compiler to optimize the code  Or  shall we say  you the programmer are responsible for optimizing the code  But it s often quite tricky and error prone    Other languages  like others already mentioned  focus more on productivity of the programmer  It is commonly believed that programmer time is much more expensive than machine time  even in the old days   So it makes a lot of sense to minimize the time programmers spend on writing and debugging programs instead of the running time of the programs  To do that  you will sacrifice a bit on what you can do to make the program faster because a lot of things are automated

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There are a lot of questions in there - mostly ones I am not qualified to answer  But for this last one       what s to stop other languages from being able to compile down to binary that runs every bit as fast as C    In a word  Abstraction    C is only one or 2 levels of abstraction away from machine language  Java and the  Net languages are at a minimum 3 levels of abstraction away from assembler  I m not sure about Python and Ruby    Typically  the more programmer toys  complex data types  etc    the further you are from machine language and the more translation has to be done    I m off here and there but that s the basic gist   Update ------- There are some good comments on this post with more details

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There isn t much that s special about C  That s one of the reasons why it s fast   Newer languages which have support for garbage collection  dynamic typing and other facilities which make it easier for the programmer to write programs    The catch is  there is additional processing overhead which will degrade the performance of the application  C doesn t have any of that  which means that there is no overhead  but that means that the programmer needs to be able to allocate memory and free them to prevent memory leaks  and must deal with static typing of variables   That said  many languages and platforms  such as Java  with its Java Virtual Machine  and  NET  with its Common Language Runtime  have improved performance over the years with advents such as just-in-time compilation which produces native machine code from bytecode to achieve higher performance

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I have found an Answer on link about why some languages are faster and some are slower  I hope this will clear more about why C or C   is faster than others  There are some other languages also that is faster than C  but we can not use all of them  Some explaination -   One of the big reasons that Fortran remains important is because it s fast  number crunching routines written in Fortran tend to be quicker than equivalent routines written in most other languages  The languages that are competing with Fortran in this space   C and C     are used because they re competitive with this performance   This raises the question  why  What is it about C   and Fortran that make them fast  and why do they outperform other popular languages  such as Java or Python   Interpreting versus compiling There are many ways to categorize and define programming languages  according to the style of programming they encourage and features they offer  When looking at performance  the biggest single distinction is between interpreted languages and compiled ones   The divide is not hard  rather  there s a spectrum  At one end  we have traditional compiled languages  a group that includes Fortran  C  and C    In these languages  there is a discrete compilation stage that translates the source code of a program into an executable form that the processor can use   This compilation process has several steps  The source code is analyzed and parsed  Basic coding mistakes such as typos and spelling errors can be detected at this point  The parsed code is used to generate an in-memory representation  which too can be used to detect mistakes   this time  semantic mistakes  such as calling functions that don t exist  or trying to perform arithmetic operations on strings of text   This in-memory representation is then used to drive a code generator  the part that produces executable code  Code optimization  to improve the performance of the generated code  is performed at various times within this process  high-level optimizations can be performed on the code representation  and lower-level optimizations are used on the output of the code generator   Actually executing the code happens later  The entire compilation process is simply used to create something that can be executed   At the opposite end  we have interpreters  The interpreters will include a parsing stage similar to that of the compiler  but this is then used to drive direct execution  with the program being run immediately   The simplest interpreter has within it executable code corresponding to the various features the language supports   so it will have functions for adding numbers  joining strings  whatever else a given language has  As it parses the code  it will look up the corresponding function and execute it  Variables created in the program will be kept in some kind of lookup table that maps their names to their data   The most extreme example of the interpreter style is something like a batch file or shell script  In these languages  the executable code is often not even built into the interpreter itself  but rather separate  standalone programs   So why does this make a difference to performance  In general  each layer of indirection reduces performance  For example  the fastest way to add two numbers is to have both of those numbers in registers in the processor  and to use the processor s add instruction  That s what compiled programs can do  they can put variables into registers and take advantage of processor instructions  But in interpreted programs  that same addition might require two lookups in a table of variables to fetch the values to add  then calling a function to perform the addition  That function may very well use the same processor instruction as the compiled program uses to perform the actual addition  but all the extra work before the instruction can actually be used makes things slower   If you want to know more please check the Source

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If you spend a month to build something in C that runs in 0 05 seconds  and I spend a day writing the same thing in Java  and it runs in 0 10 seconds  then is C really faster   But to answer your question  well-written C code will generally run faster than well-written code in other languages because part of writing C code  well  includes doing manual optimizations at a near-machine level   Although compilers are very clever indeed  they are not yet able to creatively come up with code that competes with hand-massaged algorithms  assuming the  hands  belong to a good C programmer    Edit   A lot of comments are along the lines of  I write in C and I don t think about optimizations    But to take a specific example from this post   In Delphi I could write this   function RemoveAllAFromB a  b  string   string  var   before  after  string  begin   Result    b    if 0  lt  Pos a b  then begin     before    Copy b 1 Pos a b -Length a        after    Copy b Pos a b  Length a  Length b        Result    before   after      Result    RemoveAllAFromB a Result      recursive   end  end    and in C I write this   char  s1   s2   result     original strings and the result string    int len1  len2     lengths of the strings    for  i   0  i  lt  len1  i         for  j   0  j  lt  len2  j           if  s1 i     s2 j            break                 if  j    len2        s1 i  is not found in s2          result   s1 i         result       assuming your result array is long enough             But how many optimizations are there in the C version   We make lots of decisions about implementation that I don t think about in the Delphi version   How is a string implemented   In Delphi I don t see it   In C  I ve decided it will be a pointer to an array of ASCII integers  which we call chars   In C  we test for character existence one at a time   In Delphi  I use Pos   And this is just a small example   In a large program  a C programmer has to make these kinds of low-level decisions with every few lines of code   It adds up to a hand-crafted  hand-optimized executable

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It s not so much about the language as the tools and libraries   The available libraries and compilers for C are much older than for newer languages   You might think this would make them slower  but au contraire   These libraries were written at a time when processing power and memory were at a premium   They had to be written very efficiently in order to work at all   Developers of C compilers have also had a long time to work in all sorts of clever optimizations for different processors   C s maturity and wide adoption makes for a signficant advantage over other languages of the same age   It also gives C a speed advantage over newer tools that don t emphasize raw performance as much as C had to

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The fastest running code would be carefully hand crafted machine code  Assembler will be almost as good  Both are very low level and it takes a lot of writing code to do things  C is a little above assembler  You still have the ability to control things at a very low level in the actual machine  but there is enough abstraction make writing it faster and easier then assembler  Other languages such as C  and JAVA are even more abstract  While Assembler and machine code are called low level languages  C  and JAVA  and many others  are called high level languages  C is sometimes called a middle level language

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If you spend a month to build something in C that runs in 0 05 seconds  and I spend a day writing the same thing in Java  and it runs in 0 10 seconds  then is C really faster   But to answer your question  well-written C code will generally run faster than well-written code in other languages because part of writing C code  well  includes doing manual optimizations at a near-machine level   Although compilers are very clever indeed  they are not yet able to creatively come up with code that competes with hand-massaged algorithms  assuming the  hands  belong to a good C programmer    Edit   A lot of comments are along the lines of  I write in C and I don t think about optimizations    But to take a specific example from this post   In Delphi I could write this   function RemoveAllAFromB a  b  string   string  var   before  after  string  begin   Result    b    if 0  lt  Pos a b  then begin     before    Copy b 1 Pos a b -Length a        after    Copy b Pos a b  Length a  Length b        Result    before   after      Result    RemoveAllAFromB a Result      recursive   end  end    and in C I write this   char  s1   s2   result     original strings and the result string    int len1  len2     lengths of the strings    for  i   0  i  lt  len1  i         for  j   0  j  lt  len2  j           if  s1 i     s2 j            break                 if  j    len2        s1 i  is not found in s2          result   s1 i         result       assuming your result array is long enough             But how many optimizations are there in the C version   We make lots of decisions about implementation that I don t think about in the Delphi version   How is a string implemented   In Delphi I don t see it   In C  I ve decided it will be a pointer to an array of ASCII integers  which we call chars   In C  we test for character existence one at a time   In Delphi  I use Pos   And this is just a small example   In a large program  a C programmer has to make these kinds of low-level decisions with every few lines of code   It adds up to a hand-crafted  hand-optimized executable

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There is a trade off the C designers have made  That s to say  they made the decision to put speed above safety  C won t  Check array index bounds Check for uninitialized variable values Check for memory leaks Check for null pointer dereference  When you index into an array  in Java it takes some method call in the virtual machine  bound checking and other sanity checks  That is valid and absolutely fine  because it adds safety where it s due  But in C  even pretty trivial things are not put in safety  For example  C doesn t require memcpy to check whether the regions to copy overlap  It s not designed as a language to program a big business application  But these design decisions are not bugs in the C language  They are by design  as it allows compilers and library writers to get every bit of performance out of the computer  Here is the spirit of C how the C Rationale document explains it   C code can be non-portable  Although it strove to give programmers the opportunity to write truly portable programs  the Committee did not want to force programmers into writing portably  to preclude the use of C as a   high-level assembler    the ability to write machine-specific code is one of the strengths of C  Keep the spirit of C  The Committee kept as a major goal to preserve the traditional spirit of C   There are many facets of the spirit of C  but the essence is a community sentiment of the underlying principles upon which the C language is based   Some of the facets of the spirit of C can be summarized in phrases like  Trust the programmer  Don t prevent the programmer from doing what needs to be done  Keep the language small and simple  Provide only one way to do an operation  Make it fast  even if it is not guaranteed to be portable   The last proverb needs a little explanation   The potential for efficient code generation is one of the most important strengths of C   To help ensure that no code explosion occurs for what appears to be a very simple operation  many operations are defined to be how the target machine s hardware does it rather than by a general abstract rule   An example of this willingness to live with what the machine does can be seen in the rules that govern the widening of char objects for use in expressions  whether the values of char objects widen to signed or unsigned quantities typically depends on which byte operation is more efficient on the target machine

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C is fast because it is Natively compiled  low-level language   But C is not the fastest   The Recursive Fibonacci Benchmark shows that Rust  Crystal  and Nim can be faster

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Back in the good ole days  there were just two types of languages  compiled and interpreted   Compiled languages utilized a  compiler  to read the language syntax and convert it into identical assembly language code  which could than just directly on the CPU  Interpreted languages used a couple of different schemes  but essentially the language syntax was converted into an intermediate form  and then run in a  interpreter   an environment for executing the code    Thus  in a sense  there was another  layer  -- the interpreter -- between the code and the machine  And  as always the case in a computer  more means more resources get used  Interpreters were slower  because they had to perform more operations   More recently  we ve seen more hybrid languages like Java  that employ both a compiler and an interpreter to make them work  It s complicated  but a JVM is faster  more sophisticated and way more optimized than the old interpreters  so it stands a much better change of performing  over time  closer to just straight compiled code  Of course  the newer compilers also have more fancy optimizing tricks so they tend to generate way better code than they used to as well  But most optimizations  most often  although not always  make some type of trade-off such that they are not always faster in all circumstances  Like everything else  nothing comes for free  so the optimizers must get their boast from somewhere  although often times it using compile-time CPU to save runtime CPU     Getting back to C  it is a simple language  that can be compiled into fairly optimized assembly and then run directly on the target machine  In C  if you increment an integer  it s more than likely that it is only one assembler step in the CPU  in Java however  it could end up being a lot more than that  and could include a bit of garbage collection as well  -  C offers you an abstraction that is way closer to the machine  assembler is the closest   but you end up having to do way more work to get it going and it is not as protected  easy to use or error friendly  Most other languages give you a higher abstraction and take care of more of the underlying details for you  but in exchange for their advanced functionality they require more resources to run  As you generalize some solutions  you have to handle a broader range of computing  which often requires more resources    Paul

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There are a lot of questions in there - mostly ones I am not qualified to answer  But for this last one       what s to stop other languages from being able to compile down to binary that runs every bit as fast as C    In a word  Abstraction    C is only one or 2 levels of abstraction away from machine language  Java and the  Net languages are at a minimum 3 levels of abstraction away from assembler  I m not sure about Python and Ruby    Typically  the more programmer toys  complex data types  etc    the further you are from machine language and the more translation has to be done    I m off here and there but that s the basic gist   Update ------- There are some good comments on this post with more details

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I didn t see it already  so I ll say it   C tends to be faster because almost everything else is written in C   Java is built on C  Python is built on C  or Java  or  NET  etc    Perl is  etc   The OS is written in C  the virtual machines are written in C  the compilers are written in C  the interpreters are written in C   Some things are still written in Assembly language  which tends to be even faster   More and more things are being written in something else  which is itself written in C   Each statement that you write in other languages  not Assembly  is typically implemented underneath as several statements in C  which are compiled down to native machine code   Since those other languages tend to exist in order to obtain a higher level of abstraction than C  those extra statements required in C tend to be focused on adding safety  adding complexity  and providing error handling   Those are often good things  but they have a cost  and its names are speed and size   Personally  I have written in literally dozens of languages spanning most of the available spectrum  and I personally have sought the magic that you hint at      How can I have my cake and eat it  too   How can I play with high-level abstractions in my favorite language  then drop down to the nitty gritty of C for speed    After a couple of years of research  my answer is Python  on C    You might want to give it a look   By the way  you can also drop down to Assembly from Python  too  with some minor help from a special library    On the other hand  bad code can be written in any language   Therefore  C  or Assembly  code is not automatically faster   Likewise  some optimization tricks can bring portions of higher-level language code close to the performance level of raw C   But  for most applications  your program spends most of its time waiting on people or hardware  so the difference really does not matter   Enjoy

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Back in the good ole days  there were just two types of languages  compiled and interpreted   Compiled languages utilized a  compiler  to read the language syntax and convert it into identical assembly language code  which could than just directly on the CPU  Interpreted languages used a couple of different schemes  but essentially the language syntax was converted into an intermediate form  and then run in a  interpreter   an environment for executing the code    Thus  in a sense  there was another  layer  -- the interpreter -- between the code and the machine  And  as always the case in a computer  more means more resources get used  Interpreters were slower  because they had to perform more operations   More recently  we ve seen more hybrid languages like Java  that employ both a compiler and an interpreter to make them work  It s complicated  but a JVM is faster  more sophisticated and way more optimized than the old interpreters  so it stands a much better change of performing  over time  closer to just straight compiled code  Of course  the newer compilers also have more fancy optimizing tricks so they tend to generate way better code than they used to as well  But most optimizations  most often  although not always  make some type of trade-off such that they are not always faster in all circumstances  Like everything else  nothing comes for free  so the optimizers must get their boast from somewhere  although often times it using compile-time CPU to save runtime CPU     Getting back to C  it is a simple language  that can be compiled into fairly optimized assembly and then run directly on the target machine  In C  if you increment an integer  it s more than likely that it is only one assembler step in the CPU  in Java however  it could end up being a lot more than that  and could include a bit of garbage collection as well  -  C offers you an abstraction that is way closer to the machine  assembler is the closest   but you end up having to do way more work to get it going and it is not as protected  easy to use or error friendly  Most other languages give you a higher abstraction and take care of more of the underlying details for you  but in exchange for their advanced functionality they require more resources to run  As you generalize some solutions  you have to handle a broader range of computing  which often requires more resources    Paul

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The fastest running code would be carefully hand crafted machine code  Assembler will be almost as good  Both are very low level and it takes a lot of writing code to do things  C is a little above assembler  You still have the ability to control things at a very low level in the actual machine  but there is enough abstraction make writing it faster and easier then assembler  Other languages such as C  and JAVA are even more abstract  While Assembler and machine code are called low level languages  C  and JAVA  and many others  are called high level languages  C is sometimes called a middle level language

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C is not always faster   C is slower than  for example Modern Fortran   C is often slower than Java for some things    Especially after the JIT compiler has had a go at your code   C lets pointer aliasing happen  which means some good optimizations are not possible  Particularly when you have multiple execution units  this causes data fetch stalls  Ow   The assumption that pointer arithmetic works really causes slow bloated performance on some CPU families  PIC particularly   It used to suck the big one on segmented x86   Basically  when you get a vector unit  or a parallelizing compiler  C stinks and modern Fortran runs faster   C programmer tricks like thunking   modifying the executable on the fly  cause CPU prefetch stalls   You get the drift    And our good friend  the x86  executes an instruction set that these days bears little relationship to the actual CPU architecture   Shadow registers  load-store optimizers  all in the CPU  So C is then close to the virtual metal  The real metal  Intel don t let you see   Historically VLIW CPU s were a bit of a bust so  maybe that s no so bad    If you program in C on a high-performance DSP  maybe a TI DSP     the compiler has to do some tricky stuff to unroll the C across the multiple parallel execution units  So in that case C isn t close to the metal  but it is close to the compiler  which will do whole program optimization  Weird   And finally  some CPUs  www ajile com  run Java bytecodes in hardware  C would a PITA to use on that CPU

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1  As others have said  C does less for you  No initializing variables  no array bounds checking  no memory management  etc  Those features in other languages cost memory and CPU cycles that C doesn t spend   2  Answers saying that C is less abstracted and therefore faster are only half correct I think  Technically speaking  if you had a  sufficiently advanced compiler  for language X  then language X could approach or equal the speed of C  The difference with C is that since it maps so obviously  if you ve taken an architecture course  and directly to assembly language that even a naive compiler can do a decent job  For something like Python  you need a very advanced compiler to predict the probable types of objects and generate machine code on the fly -- C s semantics are simple enough that a simple compiler can do well

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I didn t see it already  so I ll say it   C tends to be faster because almost everything else is written in C   Java is built on C  Python is built on C  or Java  or  NET  etc    Perl is  etc   The OS is written in C  the virtual machines are written in C  the compilers are written in C  the interpreters are written in C   Some things are still written in Assembly language  which tends to be even faster   More and more things are being written in something else  which is itself written in C   Each statement that you write in other languages  not Assembly  is typically implemented underneath as several statements in C  which are compiled down to native machine code   Since those other languages tend to exist in order to obtain a higher level of abstraction than C  those extra statements required in C tend to be focused on adding safety  adding complexity  and providing error handling   Those are often good things  but they have a cost  and its names are speed and size   Personally  I have written in literally dozens of languages spanning most of the available spectrum  and I personally have sought the magic that you hint at      How can I have my cake and eat it  too   How can I play with high-level abstractions in my favorite language  then drop down to the nitty gritty of C for speed    After a couple of years of research  my answer is Python  on C    You might want to give it a look   By the way  you can also drop down to Assembly from Python  too  with some minor help from a special library    On the other hand  bad code can be written in any language   Therefore  C  or Assembly  code is not automatically faster   Likewise  some optimization tricks can bring portions of higher-level language code close to the performance level of raw C   But  for most applications  your program spends most of its time waiting on people or hardware  so the difference really does not matter   Enjoy

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I have found an Answer on link about why some languages are faster and some are slower  I hope this will clear more about why C or C   is faster than others  There are some other languages also that is faster than C  but we can not use all of them  Some explaination -   One of the big reasons that Fortran remains important is because it s fast  number crunching routines written in Fortran tend to be quicker than equivalent routines written in most other languages  The languages that are competing with Fortran in this space   C and C     are used because they re competitive with this performance   This raises the question  why  What is it about C   and Fortran that make them fast  and why do they outperform other popular languages  such as Java or Python   Interpreting versus compiling There are many ways to categorize and define programming languages  according to the style of programming they encourage and features they offer  When looking at performance  the biggest single distinction is between interpreted languages and compiled ones   The divide is not hard  rather  there s a spectrum  At one end  we have traditional compiled languages  a group that includes Fortran  C  and C    In these languages  there is a discrete compilation stage that translates the source code of a program into an executable form that the processor can use   This compilation process has several steps  The source code is analyzed and parsed  Basic coding mistakes such as typos and spelling errors can be detected at this point  The parsed code is used to generate an in-memory representation  which too can be used to detect mistakes   this time  semantic mistakes  such as calling functions that don t exist  or trying to perform arithmetic operations on strings of text   This in-memory representation is then used to drive a code generator  the part that produces executable code  Code optimization  to improve the performance of the generated code  is performed at various times within this process  high-level optimizations can be performed on the code representation  and lower-level optimizations are used on the output of the code generator   Actually executing the code happens later  The entire compilation process is simply used to create something that can be executed   At the opposite end  we have interpreters  The interpreters will include a parsing stage similar to that of the compiler  but this is then used to drive direct execution  with the program being run immediately   The simplest interpreter has within it executable code corresponding to the various features the language supports   so it will have functions for adding numbers  joining strings  whatever else a given language has  As it parses the code  it will look up the corresponding function and execute it  Variables created in the program will be kept in some kind of lookup table that maps their names to their data   The most extreme example of the interpreter style is something like a batch file or shell script  In these languages  the executable code is often not even built into the interpreter itself  but rather separate  standalone programs   So why does this make a difference to performance  In general  each layer of indirection reduces performance  For example  the fastest way to add two numbers is to have both of those numbers in registers in the processor  and to use the processor s add instruction  That s what compiled programs can do  they can put variables into registers and take advantage of processor instructions  But in interpreted programs  that same addition might require two lookups in a table of variables to fetch the values to add  then calling a function to perform the addition  That function may very well use the same processor instruction as the compiled program uses to perform the actual addition  but all the extra work before the instruction can actually be used makes things slower   If you want to know more please check the Source

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The main factors are that it s a statically-typed language and that s compiled to machine code  Also  since it s a low-level language  it generally doesn t do anything you don t tell it to   These are some other factors that come to mind    Variables are not automatically initialized No bounds checking on arrays Unchecked pointer manipulation No integer overflow checking Statically-typed variables Function calls are static  unless you use function pointers  Compiler writers have had lots of time to improve the optimizing code  Also  people program in C for the purpose of getting the best performance  so there s pressure to optimize the code  Parts of the language specification are implementation-defined  so compilers are free to do things in the most optimal way   Most static-typed languages could be compiled just as fast or faster than C though  especially if they can make assumptions that C can t because of pointer aliasing  etc

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The fastest running code would be carefully hand crafted machine code  Assembler will be almost as good  Both are very low level and it takes a lot of writing code to do things  C is a little above assembler  You still have the ability to control things at a very low level in the actual machine  but there is enough abstraction make writing it faster and easier then assembler  Other languages such as C  and JAVA are even more abstract  While Assembler and machine code are called low level languages  C  and JAVA  and many others  are called high level languages  C is sometimes called a middle level language

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I know plenty of people have said it in a long winded way  but      C is faster because it does less  for you

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It is not so much that C is fast as that C s cost model is transparent   If a C program is slow  it is slow in an obvious way  by executing a lot of statements   Compared with the cost of operations in C  high-level operations on objects  especially reflection  or strings can have costs that are not obvious   Two languages that generally compile to binaries which are just as fast as C are Standard ML  using the MLton compiler  and Objective Caml    If you check out the benchmarks game you ll find that for some benchmarks  like binary trees  the OCaml version is faster than C    I didn t find any MLton entries    But don t take the shootout too seriously  it is  as it says  a game  the the results often reflect how much effort people have put in tuning the code

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With modern optimizing compilers  it s highly unlikely that a pure C program is going to be all that much faster than compiled  net code  if at all  With the productivity enhancement that frameworks like  net provide the developer  you can do things in a day that used to take weeks or months in regular C  Coupled with the cheap cost of hardware compared to a developer s salary  it s just WAY cheaper to write the stuff in a high-level language and throw hardware at any slowness   The reason Jeff and Joel talk about C being the  real programmer  language is because there is no hand-holding in C  You must allocate your own memory  deallocate that memory  do your own bounds-checking  etc  There s no such thing as new object    There s no garbage collection  classes  OOP  entity frameworks  LINQ  properties  attributes  fields  or anything like that  You have to know things like pointer arithmetic and how to dereference a pointer  And  for that matter  know and understand what a pointer is  You have to know what a stack frame is and what the instruction pointer is  You  have to know the memory model of the CPU architecture you re working on  There is a lot of implicit understanding of the architecture of a microcomputer  usually the microcomputer you re working on  when programming in C that simply is not present nor necessary when programming in something like C  or Java  All of that information has been off-loaded to the compiler  or VM  programmer

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The lack of abstraction is what makes C faster  If you write an output statement you know exactly what is happening  If you write an output statement in java it is getting compiled to a class file which then gets run on a virtual machine introducing a layor of abstraction  The lack of object oriented features as a part of the language also increases it s speed do to less code being generated  If you use C as an object oriented language then you are doing all the coding for things such as classes  inharitence  etc  This means rather then make something generalized enough for everyone with the amount of code and the performance penelty that requires you only write what you need to get the job done

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1  As others have said  C does less for you  No initializing variables  no array bounds checking  no memory management  etc  Those features in other languages cost memory and CPU cycles that C doesn t spend   2  Answers saying that C is less abstracted and therefore faster are only half correct I think  Technically speaking  if you had a  sufficiently advanced compiler  for language X  then language X could approach or equal the speed of C  The difference with C is that since it maps so obviously  if you ve taken an architecture course  and directly to assembly language that even a naive compiler can do a decent job  For something like Python  you need a very advanced compiler to predict the probable types of objects and generate machine code on the fly -- C s semantics are simple enough that a simple compiler can do well

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Amazing to see the old  C C   must be faster than Java because Java is interpreted  myth is still alive and kicking  There are articles going back a few years  as well as more recent ones  that explain with concepts or measurements why this simply isn t always the case   Current virtual machine implementations  and not just the JVM  by the way  can take advantage of information gathered during program execution to dynamically tune the code as it runs  using a variety of techniques    rendering frequent methods to machine code  inlining small methods  adjustment of locking   and a variety of other adjustments based on knowing what the code is actually doing  and on the actual characteristics of the environment in which it s running

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There are a lot of questions in there - mostly ones I am not qualified to answer  But for this last one       what s to stop other languages from being able to compile down to binary that runs every bit as fast as C    In a word  Abstraction    C is only one or 2 levels of abstraction away from machine language  Java and the  Net languages are at a minimum 3 levels of abstraction away from assembler  I m not sure about Python and Ruby    Typically  the more programmer toys  complex data types  etc    the further you are from machine language and the more translation has to be done    I m off here and there but that s the basic gist   Update ------- There are some good comments on this post with more details

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what s to stop other languages from   being able to compile down to binary   that runs every bit as fast as C    Nothing  Modern languages like Java or  NET langs are oriented more on programmer productivity rather than performance  Hardware is cheap now days  Also compilation to intermediate representation gives a lot of bonuses such as security  portability etc   NET CLR can take advantage of different hardware - for example you don t need to manually optimize recompile program to use SSE instructions set

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Many of these answers give valid reasons for why C is  or is not  faster  either in general or in specific scenarios    It s undeniable that    Many other languages provide automatic features that we take for granted   Bounds checking  run-time type checking  and automatic memory management  for example  don t come for free   There is at least some cost associated with these features  which we may not think about   or even realize   while writing code that uses these features  The step from source to machine is often not as direct in other languages as it is in C  OTOH  to say that compiled C code executes faster than other code written in other languages is a generalization that isn t always true   Counter-examples are easy to find  or contrive     All of this notwithstanding  there is something else I have noticed that  I think  affects the comparative performance of C vs  many other languages more greatly than any other factor   To wit   Other languages often make it easier to write code that executes more slowly   Often  it s even encouraged by the design philosophies of the language   Corollary  a C programmer is more likely to write code that doesn t perform unnecessary operations   As an example  consider a simple Windows program in which a single main window is created   A C version would populate a WNDCLASS EX  structure which would be passed to RegisterClass Ex   then call CreateWindow Ex  and enter a message loop   Highly simplified and abbreviated code follows   WNDCLASS wc  MSG      msg   wc style           0  wc lpfnWndProc      amp WndProc  wc cbClsExtra      0  wc cbWndExtra      0  wc hInstance       hInstance  wc hIcon           NULL  wc hCursor         LoadCursor NULL  IDC ARROW   wc hbrBackground    HBRUSH  COLOR BTNFACE   1   wc lpszMenuName    NULL  wc lpszClassName    MainWndCls    RegisterClass  amp wc    CreateWindow  MainWndCls       WS OVERLAPPEDWINDOW   WS VISIBLE               CW USEDEFAULT  0  CW USEDEFAULT  0  NULL  NULL  hInstance  NULL    while GetMessage  amp msg  NULL  0  0        TranslateMessage  amp msg       DispatchMessage  amp msg       An equivalent program in C  could be just one line of code   Application Run new Form       This one line of code provides all of the functionality that nearly 20 lines of C code did  and adds some things we left out  such as error checking   The richer  fuller library  compared to those used in a typical C project  did a lot of work for us  freeing our time to write many more snippets of code that look short to us but involve many steps behind the scenes   But a rich library enabling easy and quick code bloat isn t really my point   My point is more apparent when you start examining what actually happens when our little one-liner actually executes   For fun sometime  enable  NET source access in Visual Studio 2008 or higher  and step into the simple one-linef above   One of the fun little gems you ll come across is this comment in the getter for Control CreateParams      In a typical control this is accessed ten times to create and show a control     It is a net memory savings  then  to maintain a copy on control      if  createParams    null        createParams   new CreateParams          Ten times   The information roughly equivalent to the sum of what s stored in a WNDCLASSEX structure and what s passed to CreateWindowEx is retrieved from the Control class ten times before it s stored in a WNDCLASSEX structure and passed on to RegisterClassEx and CreateWindowEx   All in all  the number of instructions executed to perform this very basic task is 2   3 orders of magnitude more in C  than in C   Part of this is due to the use of a feature-rich library  which is necessarily generalized  versus our simple C code which does exactly what we need and nothing more   But part of it is due to the fact that the modularized  object-oriented nature of  NET framework  lends itself to a lot of repetition of execution that often is avoided by a procedural approach   I m not trying to pick on C  or the  NET framework   Nor am I saying that modularization  generalization  library language features  OOP  etc  are bad things   I used to do most of my development in C  later in C    and most lately in C    Similarly  before C  I used mostly assembly   And with each step  higher  my language goes  I write better  more maintainable  more robust programs in less time   They do  however  tend to execute a little more slowly

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It is not so much that C is fast as that C s cost model is transparent   If a C program is slow  it is slow in an obvious way  by executing a lot of statements   Compared with the cost of operations in C  high-level operations on objects  especially reflection  or strings can have costs that are not obvious   Two languages that generally compile to binaries which are just as fast as C are Standard ML  using the MLton compiler  and Objective Caml    If you check out the benchmarks game you ll find that for some benchmarks  like binary trees  the OCaml version is faster than C    I didn t find any MLton entries    But don t take the shootout too seriously  it is  as it says  a game  the the results often reflect how much effort people have put in tuning the code

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Amazing to see the old  C C   must be faster than Java because Java is interpreted  myth is still alive and kicking  There are articles going back a few years  as well as more recent ones  that explain with concepts or measurements why this simply isn t always the case   Current virtual machine implementations  and not just the JVM  by the way  can take advantage of information gathered during program execution to dynamically tune the code as it runs  using a variety of techniques    rendering frequent methods to machine code  inlining small methods  adjustment of locking   and a variety of other adjustments based on knowing what the code is actually doing  and on the actual characteristics of the environment in which it s running

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There isn t much that s special about C  That s one of the reasons why it s fast   Newer languages which have support for garbage collection  dynamic typing and other facilities which make it easier for the programmer to write programs    The catch is  there is additional processing overhead which will degrade the performance of the application  C doesn t have any of that  which means that there is no overhead  but that means that the programmer needs to be able to allocate memory and free them to prevent memory leaks  and must deal with static typing of variables   That said  many languages and platforms  such as Java  with its Java Virtual Machine  and  NET  with its Common Language Runtime  have improved performance over the years with advents such as just-in-time compilation which produces native machine code from bytecode to achieve higher performance

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If you spend a month to build something in C that runs in 0 05 seconds  and I spend a day writing the same thing in Java  and it runs in 0 10 seconds  then is C really faster   But to answer your question  well-written C code will generally run faster than well-written code in other languages because part of writing C code  well  includes doing manual optimizations at a near-machine level   Although compilers are very clever indeed  they are not yet able to creatively come up with code that competes with hand-massaged algorithms  assuming the  hands  belong to a good C programmer    Edit   A lot of comments are along the lines of  I write in C and I don t think about optimizations    But to take a specific example from this post   In Delphi I could write this   function RemoveAllAFromB a  b  string   string  var   before  after  string  begin   Result    b    if 0  lt  Pos a b  then begin     before    Copy b 1 Pos a b -Length a        after    Copy b Pos a b  Length a  Length b        Result    before   after      Result    RemoveAllAFromB a Result      recursive   end  end    and in C I write this   char  s1   s2   result     original strings and the result string    int len1  len2     lengths of the strings    for  i   0  i  lt  len1  i         for  j   0  j  lt  len2  j           if  s1 i     s2 j            break                 if  j    len2        s1 i  is not found in s2          result   s1 i         result       assuming your result array is long enough             But how many optimizations are there in the C version   We make lots of decisions about implementation that I don t think about in the Delphi version   How is a string implemented   In Delphi I don t see it   In C  I ve decided it will be a pointer to an array of ASCII integers  which we call chars   In C  we test for character existence one at a time   In Delphi  I use Pos   And this is just a small example   In a large program  a C programmer has to make these kinds of low-level decisions with every few lines of code   It adds up to a hand-crafted  hand-optimized executable

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C   is faster on average  as it was initially  largely a superset of C  though there are some differences   However  for specific benchmarks  there is often another language which is faster   https   benchmarksgame-team pages debian net benchmarksgame   fannjuch-redux was fastest in Scala  n-body and fasta were faster in Ada   spectral-norm was fastest in Fortran   reverse-complement  mandelbrot and pidigits were fastest in ATS   regex-dna was fastest in JavaScript   chameneou-redux was fastest is Java 7   thread-ring was fastest in Haskell   The rest of the benchmarks were fastest in C or C

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I don t think anyone has mentioned the fact that much more effort has been put into C compilers than any other compiler   with perhaps the exception of Java      C is extremely optimize-able for many of the reasons already stated - more than almost any other language    So if the same amount of effort is put into other language compilers  C will probably still come out on top        I think there is at least one candidate language that with effort could be optimized better than C and thus we could see implementations that produce faster binaries    I m thinking of digital mars D because the creator took care to build a language that could potentially be better optimized than C    There may be other languages that have this possibility   However I cannot imagine that any language will have compilers more than just a few percent faster than the best C compilers   I would love to be wrong     I think the real  low hanging fruit  will be in languages that are designed to be EASY for humans to optimize    A skilled programmer can make any language go faster - but sometimes you have to do ridiculous things or use unnatural constructs to make this happen    Although it will always take effort   a good language should produce relatively fast code without having to obsess over exactly how the program is written   It s also important  at least to me  that the worst case code tends to be fast    There are numerous  proofs  on the web that Java is as fast or faster than C   but that is based on cherry picking examples   I m not big fan of C   but I know that ANYTHING I write in C is going to run well    With Java it will  probably  run within 15  of the speed   usually within 25  but in some cases it can be far worse   Any cases where it s just as fast or within a couple of percent are usually due to most of the time being spent in the library code which is heavily optimized C anyway

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It s not so much about the language as the tools and libraries   The available libraries and compilers for C are much older than for newer languages   You might think this would make them slower  but au contraire   These libraries were written at a time when processing power and memory were at a premium   They had to be written very efficiently in order to work at all   Developers of C compilers have also had a long time to work in all sorts of clever optimizations for different processors   C s maturity and wide adoption makes for a signficant advantage over other languages of the same age   It also gives C a speed advantage over newer tools that don t emphasize raw performance as much as C had to

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Back in the good ole days  there were just two types of languages  compiled and interpreted   Compiled languages utilized a  compiler  to read the language syntax and convert it into identical assembly language code  which could than just directly on the CPU  Interpreted languages used a couple of different schemes  but essentially the language syntax was converted into an intermediate form  and then run in a  interpreter   an environment for executing the code    Thus  in a sense  there was another  layer  -- the interpreter -- between the code and the machine  And  as always the case in a computer  more means more resources get used  Interpreters were slower  because they had to perform more operations   More recently  we ve seen more hybrid languages like Java  that employ both a compiler and an interpreter to make them work  It s complicated  but a JVM is faster  more sophisticated and way more optimized than the old interpreters  so it stands a much better change of performing  over time  closer to just straight compiled code  Of course  the newer compilers also have more fancy optimizing tricks so they tend to generate way better code than they used to as well  But most optimizations  most often  although not always  make some type of trade-off such that they are not always faster in all circumstances  Like everything else  nothing comes for free  so the optimizers must get their boast from somewhere  although often times it using compile-time CPU to save runtime CPU     Getting back to C  it is a simple language  that can be compiled into fairly optimized assembly and then run directly on the target machine  In C  if you increment an integer  it s more than likely that it is only one assembler step in the CPU  in Java however  it could end up being a lot more than that  and could include a bit of garbage collection as well  -  C offers you an abstraction that is way closer to the machine  assembler is the closest   but you end up having to do way more work to get it going and it is not as protected  easy to use or error friendly  Most other languages give you a higher abstraction and take care of more of the underlying details for you  but in exchange for their advanced functionality they require more resources to run  As you generalize some solutions  you have to handle a broader range of computing  which often requires more resources    Paul

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I guess you forgot that Assembly language is also a language     But seriously  C programs are faster only when the programmer knows what he s doing  You can easily write a C program that runs slower than programs written in other languages that do the same job   The reason why C is faster is because it is designed in this way  It lets you do a lot of  lower level  stuff that helps the compiler to optimize the code  Or  shall we say  you the programmer are responsible for optimizing the code  But it s often quite tricky and error prone    Other languages  like others already mentioned  focus more on productivity of the programmer  It is commonly believed that programmer time is much more expensive than machine time  even in the old days   So it makes a lot of sense to minimize the time programmers spend on writing and debugging programs instead of the running time of the programs  To do that  you will sacrifice a bit on what you can do to make the program faster because a lot of things are automated

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Setting aside advanced optimization techniques such as hot-spot optimization  pre-compiled meta-algorithms  and various forms of parallelism  the fundamental speed of a language correlates strongly with the implicit behind-the-scenes complexity required to support the operations that would commonly be specified within inner loops   Perhaps the most obvious is validity checking on indirect memory references -- such as checking pointers for null and checking indexes against array boundaries   Most high-level languages perform these checks implicitly  but C does not   However  this is not necessarily a fundamental limitation of these other languages -- a sufficiently clever compiler may be capable of removing these checks from the inner loops of an algorithm through some form of loop-invariant code motion   The more fundamental advantage of C  and to a similar extent the closely related C    is a heavy reliance on stack-based memory allocation  which is inherently fast for allocation  deallocation  and access   In C  and C    the primary call stack can be used for allocation of primitives  arrays  and aggregates  struct class      While C does offer the capability to dynamically allocate memory of arbitrary size and lifetime  using the so called  heap    doing so is avoided by default  the stack is used instead    Tantalizingly  it is sometimes possible to replicate the C memory allocation strategy within the runtime environments of other programming languages   This has been demonstrated by asm js  which allows code written in C or C   to be translated into a subset of JavaScript and run safely in a web browser environment -- with near-native speed     As somewhat of an aside  another area where C and C   outshine most other languages for speed is the ability to seamlessly integrate with native machine instruction sets   A notable example of this is the  compiler and platform dependent  availability of SIMD intrinsics which support the construction of custom algorithms that take advantage of the now nearly ubiquitous parallel processing hardware -- while still utilizing the data allocation abstractions provided by the language  lower-level register allocation is managed by the compiler

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I don t think anyone has mentioned the fact that much more effort has been put into C compilers than any other compiler   with perhaps the exception of Java      C is extremely optimize-able for many of the reasons already stated - more than almost any other language    So if the same amount of effort is put into other language compilers  C will probably still come out on top        I think there is at least one candidate language that with effort could be optimized better than C and thus we could see implementations that produce faster binaries    I m thinking of digital mars D because the creator took care to build a language that could potentially be better optimized than C    There may be other languages that have this possibility   However I cannot imagine that any language will have compilers more than just a few percent faster than the best C compilers   I would love to be wrong     I think the real  low hanging fruit  will be in languages that are designed to be EASY for humans to optimize    A skilled programmer can make any language go faster - but sometimes you have to do ridiculous things or use unnatural constructs to make this happen    Although it will always take effort   a good language should produce relatively fast code without having to obsess over exactly how the program is written   It s also important  at least to me  that the worst case code tends to be fast    There are numerous  proofs  on the web that Java is as fast or faster than C   but that is based on cherry picking examples   I m not big fan of C   but I know that ANYTHING I write in C is going to run well    With Java it will  probably  run within 15  of the speed   usually within 25  but in some cases it can be far worse   Any cases where it s just as fast or within a couple of percent are usually due to most of the time being spent in the library code which is heavily optimized C anyway

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I didn t see it already  so I ll say it   C tends to be faster because almost everything else is written in C   Java is built on C  Python is built on C  or Java  or  NET  etc    Perl is  etc   The OS is written in C  the virtual machines are written in C  the compilers are written in C  the interpreters are written in C   Some things are still written in Assembly language  which tends to be even faster   More and more things are being written in something else  which is itself written in C   Each statement that you write in other languages  not Assembly  is typically implemented underneath as several statements in C  which are compiled down to native machine code   Since those other languages tend to exist in order to obtain a higher level of abstraction than C  those extra statements required in C tend to be focused on adding safety  adding complexity  and providing error handling   Those are often good things  but they have a cost  and its names are speed and size   Personally  I have written in literally dozens of languages spanning most of the available spectrum  and I personally have sought the magic that you hint at      How can I have my cake and eat it  too   How can I play with high-level abstractions in my favorite language  then drop down to the nitty gritty of C for speed    After a couple of years of research  my answer is Python  on C    You might want to give it a look   By the way  you can also drop down to Assembly from Python  too  with some minor help from a special library    On the other hand  bad code can be written in any language   Therefore  C  or Assembly  code is not automatically faster   Likewise  some optimization tricks can bring portions of higher-level language code close to the performance level of raw C   But  for most applications  your program spends most of its time waiting on people or hardware  so the difference really does not matter   Enjoy

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For the most part  every C instruction corresponds to a very few assembler instructions   You are essentially writing higher level machine code  so you have control over almost everything the processor does   Many other compiled languages  such as C    have a lot of simple looking instructions that can turn into much more code than you think it does  virtual functions  copy constructors  etc     And interpreted languages like Java or Ruby have another layer of instructions that you never see - the Virtual Machine or Interpreter

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There are a many reasons  including   It compiles into assembly language  It is statically typed  No garbage collection  No exception mechanism  Compiler optimizations Part of the philosophy of C is to keep things simple and maintain backwards compatibility  instead of adding more features

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Just step through the machine code in your IDE, and you'll see why it's faster (if it's faster). It leaves out a lot of hand-holding. Chances are your Cxx can also be told to leave it out too, in which case it should be about the same.

Compiler optimizations are overrated, as are almost all perceptions about language speed.

Optimization of generated code only makes a difference in hotspot code, that is, tight algorithms devoid of function calls (explicit or implicit). Anywhere else, it achieves very little.

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With modern optimizing compilers  it s highly unlikely that a pure C program is going to be all that much faster than compiled  net code  if at all  With the productivity enhancement that frameworks like  net provide the developer  you can do things in a day that used to take weeks or months in regular C  Coupled with the cheap cost of hardware compared to a developer s salary  it s just WAY cheaper to write the stuff in a high-level language and throw hardware at any slowness   The reason Jeff and Joel talk about C being the  real programmer  language is because there is no hand-holding in C  You must allocate your own memory  deallocate that memory  do your own bounds-checking  etc  There s no such thing as new object    There s no garbage collection  classes  OOP  entity frameworks  LINQ  properties  attributes  fields  or anything like that  You have to know things like pointer arithmetic and how to dereference a pointer  And  for that matter  know and understand what a pointer is  You have to know what a stack frame is and what the instruction pointer is  You  have to know the memory model of the CPU architecture you re working on  There is a lot of implicit understanding of the architecture of a microcomputer  usually the microcomputer you re working on  when programming in C that simply is not present nor necessary when programming in something like C  or Java  All of that information has been off-loaded to the compiler  or VM  programmer

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Many of these answers give valid reasons for why C is  or is not  faster  either in general or in specific scenarios    It s undeniable that    Many other languages provide automatic features that we take for granted   Bounds checking  run-time type checking  and automatic memory management  for example  don t come for free   There is at least some cost associated with these features  which we may not think about   or even realize   while writing code that uses these features  The step from source to machine is often not as direct in other languages as it is in C  OTOH  to say that compiled C code executes faster than other code written in other languages is a generalization that isn t always true   Counter-examples are easy to find  or contrive     All of this notwithstanding  there is something else I have noticed that  I think  affects the comparative performance of C vs  many other languages more greatly than any other factor   To wit   Other languages often make it easier to write code that executes more slowly   Often  it s even encouraged by the design philosophies of the language   Corollary  a C programmer is more likely to write code that doesn t perform unnecessary operations   As an example  consider a simple Windows program in which a single main window is created   A C version would populate a WNDCLASS EX  structure which would be passed to RegisterClass Ex   then call CreateWindow Ex  and enter a message loop   Highly simplified and abbreviated code follows   WNDCLASS wc  MSG      msg   wc style           0  wc lpfnWndProc      amp WndProc  wc cbClsExtra      0  wc cbWndExtra      0  wc hInstance       hInstance  wc hIcon           NULL  wc hCursor         LoadCursor NULL  IDC ARROW   wc hbrBackground    HBRUSH  COLOR BTNFACE   1   wc lpszMenuName    NULL  wc lpszClassName    MainWndCls    RegisterClass  amp wc    CreateWindow  MainWndCls       WS OVERLAPPEDWINDOW   WS VISIBLE               CW USEDEFAULT  0  CW USEDEFAULT  0  NULL  NULL  hInstance  NULL    while GetMessage  amp msg  NULL  0  0        TranslateMessage  amp msg       DispatchMessage  amp msg       An equivalent program in C  could be just one line of code   Application Run new Form       This one line of code provides all of the functionality that nearly 20 lines of C code did  and adds some things we left out  such as error checking   The richer  fuller library  compared to those used in a typical C project  did a lot of work for us  freeing our time to write many more snippets of code that look short to us but involve many steps behind the scenes   But a rich library enabling easy and quick code bloat isn t really my point   My point is more apparent when you start examining what actually happens when our little one-liner actually executes   For fun sometime  enable  NET source access in Visual Studio 2008 or higher  and step into the simple one-linef above   One of the fun little gems you ll come across is this comment in the getter for Control CreateParams      In a typical control this is accessed ten times to create and show a control     It is a net memory savings  then  to maintain a copy on control      if  createParams    null        createParams   new CreateParams          Ten times   The information roughly equivalent to the sum of what s stored in a WNDCLASSEX structure and what s passed to CreateWindowEx is retrieved from the Control class ten times before it s stored in a WNDCLASSEX structure and passed on to RegisterClassEx and CreateWindowEx   All in all  the number of instructions executed to perform this very basic task is 2   3 orders of magnitude more in C  than in C   Part of this is due to the use of a feature-rich library  which is necessarily generalized  versus our simple C code which does exactly what we need and nothing more   But part of it is due to the fact that the modularized  object-oriented nature of  NET framework  lends itself to a lot of repetition of execution that often is avoided by a procedural approach   I m not trying to pick on C  or the  NET framework   Nor am I saying that modularization  generalization  library language features  OOP  etc  are bad things   I used to do most of my development in C  later in C    and most lately in C    Similarly  before C  I used mostly assembly   And with each step  higher  my language goes  I write better  more maintainable  more robust programs in less time   They do  however  tend to execute a little more slowly

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Even the difference between C and C   can at times be great   When you are allocating memory for an object  invoking constructors  aligning memory on word boundaries  etc  the program winds up going through a lot of overhead that is abstracted away from the programmer   C forces you to take a look at each thing that your program is doing  generally at a very fine level of detail   This makes it harder  although not by any means impossible  to write code that does a lot of tasks that are unnecessary to the immediate goal at hand   So where in  for instance a BASIC program you would use the INPUT keyword to read a string form STDIN and automatically allocate memory for its variable  in C the programmer will typically have already allocated memory and can control things like whether the program blocks for I O or not  and if it stops reading input after it has the information it needs or continues reading characters to the end of the line   C also performs a lot less error-checking than other languages  presuming the programmer knows what they re doing   So whereas in PHP if you declare a string  myStr   getInput    and go on to reference  myStr 20   but the input was only 10 characters long  PHP will catch this and safely return to you a blank string   C assumes that you ve either allocated enough memory to hold data past the end of the string or that you know what information comes after the string and are trying to reference that instead   These small factors have a huge impact on overhead in aggregate

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C is fast because it is Natively compiled  low-level language   But C is not the fastest   The Recursive Fibonacci Benchmark shows that Rust  Crystal  and Nim can be faster

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I guess you forgot that Assembly language is also a language     But seriously  C programs are faster only when the programmer knows what he s doing  You can easily write a C program that runs slower than programs written in other languages that do the same job   The reason why C is faster is because it is designed in this way  It lets you do a lot of  lower level  stuff that helps the compiler to optimize the code  Or  shall we say  you the programmer are responsible for optimizing the code  But it s often quite tricky and error prone    Other languages  like others already mentioned  focus more on productivity of the programmer  It is commonly believed that programmer time is much more expensive than machine time  even in the old days   So it makes a lot of sense to minimize the time programmers spend on writing and debugging programs instead of the running time of the programs  To do that  you will sacrifice a bit on what you can do to make the program faster because a lot of things are automated

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Amazing to see the old  C C   must be faster than Java because Java is interpreted  myth is still alive and kicking  There are articles going back a few years  as well as more recent ones  that explain with concepts or measurements why this simply isn t always the case   Current virtual machine implementations  and not just the JVM  by the way  can take advantage of information gathered during program execution to dynamically tune the code as it runs  using a variety of techniques    rendering frequent methods to machine code  inlining small methods  adjustment of locking   and a variety of other adjustments based on knowing what the code is actually doing  and on the actual characteristics of the environment in which it s running

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Some C   algorithms are faster than C  and some implementations of algorithms or design patterns in other languages can be faster than C   When people say that C is fast  and then move on to talking about some other language  they are generally using C s performance as a benchmark

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Even the difference between C and C   can at times be great   When you are allocating memory for an object  invoking constructors  aligning memory on word boundaries  etc  the program winds up going through a lot of overhead that is abstracted away from the programmer   C forces you to take a look at each thing that your program is doing  generally at a very fine level of detail   This makes it harder  although not by any means impossible  to write code that does a lot of tasks that are unnecessary to the immediate goal at hand   So where in  for instance a BASIC program you would use the INPUT keyword to read a string form STDIN and automatically allocate memory for its variable  in C the programmer will typically have already allocated memory and can control things like whether the program blocks for I O or not  and if it stops reading input after it has the information it needs or continues reading characters to the end of the line   C also performs a lot less error-checking than other languages  presuming the programmer knows what they re doing   So whereas in PHP if you declare a string  myStr   getInput    and go on to reference  myStr 20   but the input was only 10 characters long  PHP will catch this and safely return to you a blank string   C assumes that you ve either allocated enough memory to hold data past the end of the string or that you know what information comes after the string and are trying to reference that instead   These small factors have a huge impact on overhead in aggregate

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It is not so much that C is fast as that C s cost model is transparent   If a C program is slow  it is slow in an obvious way  by executing a lot of statements   Compared with the cost of operations in C  high-level operations on objects  especially reflection  or strings can have costs that are not obvious   Two languages that generally compile to binaries which are just as fast as C are Standard ML  using the MLton compiler  and Objective Caml    If you check out the benchmarks game you ll find that for some benchmarks  like binary trees  the OCaml version is faster than C    I didn t find any MLton entries    But don t take the shootout too seriously  it is  as it says  a game  the the results often reflect how much effort people have put in tuning the code

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what s to stop other languages from   being able to compile down to binary   that runs every bit as fast as C    Nothing  Modern languages like Java or  NET langs are oriented more on programmer productivity rather than performance  Hardware is cheap now days  Also compilation to intermediate representation gives a lot of bonuses such as security  portability etc   NET CLR can take advantage of different hardware - for example you don t need to manually optimize recompile program to use SSE instructions set

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It is not so much that C is fast as that C s cost model is transparent   If a C program is slow  it is slow in an obvious way  by executing a lot of statements   Compared with the cost of operations in C  high-level operations on objects  especially reflection  or strings can have costs that are not obvious   Two languages that generally compile to binaries which are just as fast as C are Standard ML  using the MLton compiler  and Objective Caml    If you check out the benchmarks game you ll find that for some benchmarks  like binary trees  the OCaml version is faster than C    I didn t find any MLton entries    But don t take the shootout too seriously  it is  as it says  a game  the the results often reflect how much effort people have put in tuning the code

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There is a trade off the C designers have made  That s to say  they made the decision to put speed above safety  C won t  Check array index bounds Check for uninitialized variable values Check for memory leaks Check for null pointer dereference  When you index into an array  in Java it takes some method call in the virtual machine  bound checking and other sanity checks  That is valid and absolutely fine  because it adds safety where it s due  But in C  even pretty trivial things are not put in safety  For example  C doesn t require memcpy to check whether the regions to copy overlap  It s not designed as a language to program a big business application  But these design decisions are not bugs in the C language  They are by design  as it allows compilers and library writers to get every bit of performance out of the computer  Here is the spirit of C how the C Rationale document explains it   C code can be non-portable  Although it strove to give programmers the opportunity to write truly portable programs  the Committee did not want to force programmers into writing portably  to preclude the use of C as a   high-level assembler    the ability to write machine-specific code is one of the strengths of C  Keep the spirit of C  The Committee kept as a major goal to preserve the traditional spirit of C   There are many facets of the spirit of C  but the essence is a community sentiment of the underlying principles upon which the C language is based   Some of the facets of the spirit of C can be summarized in phrases like  Trust the programmer  Don t prevent the programmer from doing what needs to be done  Keep the language small and simple  Provide only one way to do an operation  Make it fast  even if it is not guaranteed to be portable   The last proverb needs a little explanation   The potential for efficient code generation is one of the most important strengths of C   To help ensure that no code explosion occurs for what appears to be a very simple operation  many operations are defined to be how the target machine s hardware does it rather than by a general abstract rule   An example of this willingness to live with what the machine does can be seen in the rules that govern the widening of char objects for use in expressions  whether the values of char objects widen to signed or unsigned quantities typically depends on which byte operation is more efficient on the target machine

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There is a trade off the C designers have made  That s to say  they made the decision to put speed above safety  C won t  Check array index bounds Check for uninitialized variable values Check for memory leaks Check for null pointer dereference  When you index into an array  in Java it takes some method call in the virtual machine  bound checking and other sanity checks  That is valid and absolutely fine  because it adds safety where it s due  But in C  even pretty trivial things are not put in safety  For example  C doesn t require memcpy to check whether the regions to copy overlap  It s not designed as a language to program a big business application  But these design decisions are not bugs in the C language  They are by design  as it allows compilers and library writers to get every bit of performance out of the computer  Here is the spirit of C how the C Rationale document explains it   C code can be non-portable  Although it strove to give programmers the opportunity to write truly portable programs  the Committee did not want to force programmers into writing portably  to preclude the use of C as a   high-level assembler    the ability to write machine-specific code is one of the strengths of C  Keep the spirit of C  The Committee kept as a major goal to preserve the traditional spirit of C   There are many facets of the spirit of C  but the essence is a community sentiment of the underlying principles upon which the C language is based   Some of the facets of the spirit of C can be summarized in phrases like  Trust the programmer  Don t prevent the programmer from doing what needs to be done  Keep the language small and simple  Provide only one way to do an operation  Make it fast  even if it is not guaranteed to be portable   The last proverb needs a little explanation   The potential for efficient code generation is one of the most important strengths of C   To help ensure that no code explosion occurs for what appears to be a very simple operation  many operations are defined to be how the target machine s hardware does it rather than by a general abstract rule   An example of this willingness to live with what the machine does can be seen in the rules that govern the widening of char objects for use in expressions  whether the values of char objects widen to signed or unsigned quantities typically depends on which byte operation is more efficient on the target machine

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1  As others have said  C does less for you  No initializing variables  no array bounds checking  no memory management  etc  Those features in other languages cost memory and CPU cycles that C doesn t spend   2  Answers saying that C is less abstracted and therefore faster are only half correct I think  Technically speaking  if you had a  sufficiently advanced compiler  for language X  then language X could approach or equal the speed of C  The difference with C is that since it maps so obviously  if you ve taken an architecture course  and directly to assembly language that even a naive compiler can do a decent job  For something like Python  you need a very advanced compiler to predict the probable types of objects and generate machine code on the fly -- C s semantics are simple enough that a simple compiler can do well

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what s to stop other languages from   being able to compile down to binary   that runs every bit as fast as C    Nothing  Modern languages like Java or  NET langs are oriented more on programmer productivity rather than performance  Hardware is cheap now days  Also compilation to intermediate representation gives a lot of bonuses such as security  portability etc   NET CLR can take advantage of different hardware - for example you don t need to manually optimize recompile program to use SSE instructions set

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The lack of abstraction is what makes C faster  If you write an output statement you know exactly what is happening  If you write an output statement in java it is getting compiled to a class file which then gets run on a virtual machine introducing a layor of abstraction  The lack of object oriented features as a part of the language also increases it s speed do to less code being generated  If you use C as an object oriented language then you are doing all the coding for things such as classes  inharitence  etc  This means rather then make something generalized enough for everyone with the amount of code and the performance penelty that requires you only write what you need to get the job done

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There isn t much that s special about C  That s one of the reasons why it s fast   Newer languages which have support for garbage collection  dynamic typing and other facilities which make it easier for the programmer to write programs    The catch is  there is additional processing overhead which will degrade the performance of the application  C doesn t have any of that  which means that there is no overhead  but that means that the programmer needs to be able to allocate memory and free them to prevent memory leaks  and must deal with static typing of variables   That said  many languages and platforms  such as Java  with its Java Virtual Machine  and  NET  with its Common Language Runtime  have improved performance over the years with advents such as just-in-time compilation which produces native machine code from bytecode to achieve higher performance

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C   is faster on average  as it was initially  largely a superset of C  though there are some differences   However  for specific benchmarks  there is often another language which is faster   https   benchmarksgame-team pages debian net benchmarksgame   fannjuch-redux was fastest in Scala  n-body and fasta were faster in Ada   spectral-norm was fastest in Fortran   reverse-complement  mandelbrot and pidigits were fastest in ATS   regex-dna was fastest in JavaScript   chameneou-redux was fastest is Java 7   thread-ring was fastest in Haskell   The rest of the benchmarks were fastest in C or C

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With modern optimizing compilers  it s highly unlikely that a pure C program is going to be all that much faster than compiled  net code  if at all  With the productivity enhancement that frameworks like  net provide the developer  you can do things in a day that used to take weeks or months in regular C  Coupled with the cheap cost of hardware compared to a developer s salary  it s just WAY cheaper to write the stuff in a high-level language and throw hardware at any slowness   The reason Jeff and Joel talk about C being the  real programmer  language is because there is no hand-holding in C  You must allocate your own memory  deallocate that memory  do your own bounds-checking  etc  There s no such thing as new object    There s no garbage collection  classes  OOP  entity frameworks  LINQ  properties  attributes  fields  or anything like that  You have to know things like pointer arithmetic and how to dereference a pointer  And  for that matter  know and understand what a pointer is  You have to know what a stack frame is and what the instruction pointer is  You  have to know the memory model of the CPU architecture you re working on  There is a lot of implicit understanding of the architecture of a microcomputer  usually the microcomputer you re working on  when programming in C that simply is not present nor necessary when programming in something like C  or Java  All of that information has been off-loaded to the compiler  or VM  programmer

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It s all about time and effort   Given an infinite amount of time and effort    An assembly program will be faster than one written in C  A C program will be faster than one written in C      Given an fixed amount of time and effort    A C   program will be faster than one written in C  A C program will be faster than one written in Assembly    Why  Because the more abstraction you do  the more time you can spend optimising the critical sections of code that really matter  A couple of assumptions here is a developer is equally competent in all three languages  you don t care about binary size  memory usage  etc   Every abstraction has a cost performance-wise but should make code easier and faster to write

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Back in the good ole days  there were just two types of languages  compiled and interpreted   Compiled languages utilized a  compiler  to read the language syntax and convert it into identical assembly language code  which could than just directly on the CPU  Interpreted languages used a couple of different schemes  but essentially the language syntax was converted into an intermediate form  and then run in a  interpreter   an environment for executing the code    Thus  in a sense  there was another  layer  -- the interpreter -- between the code and the machine  And  as always the case in a computer  more means more resources get used  Interpreters were slower  because they had to perform more operations   More recently  we ve seen more hybrid languages like Java  that employ both a compiler and an interpreter to make them work  It s complicated  but a JVM is faster  more sophisticated and way more optimized than the old interpreters  so it stands a much better change of performing  over time  closer to just straight compiled code  Of course  the newer compilers also have more fancy optimizing tricks so they tend to generate way better code than they used to as well  But most optimizations  most often  although not always  make some type of trade-off such that they are not always faster in all circumstances  Like everything else  nothing comes for free  so the optimizers must get their boast from somewhere  although often times it using compile-time CPU to save runtime CPU     Getting back to C  it is a simple language  that can be compiled into fairly optimized assembly and then run directly on the target machine  In C  if you increment an integer  it s more than likely that it is only one assembler step in the CPU  in Java however  it could end up being a lot more than that  and could include a bit of garbage collection as well  -  C offers you an abstraction that is way closer to the machine  assembler is the closest   but you end up having to do way more work to get it going and it is not as protected  easy to use or error friendly  Most other languages give you a higher abstraction and take care of more of the underlying details for you  but in exchange for their advanced functionality they require more resources to run  As you generalize some solutions  you have to handle a broader range of computing  which often requires more resources    Paul

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I guess you forgot that Assembly language is also a language     But seriously  C programs are faster only when the programmer knows what he s doing  You can easily write a C program that runs slower than programs written in other languages that do the same job   The reason why C is faster is because it is designed in this way  It lets you do a lot of  lower level  stuff that helps the compiler to optimize the code  Or  shall we say  you the programmer are responsible for optimizing the code  But it s often quite tricky and error prone    Other languages  like others already mentioned  focus more on productivity of the programmer  It is commonly believed that programmer time is much more expensive than machine time  even in the old days   So it makes a lot of sense to minimize the time programmers spend on writing and debugging programs instead of the running time of the programs  To do that  you will sacrifice a bit on what you can do to make the program faster because a lot of things are automated

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This is actually a bit of a perpetuated falsehood   While it is true that C programs are frequently faster  this is not always the case  especially if the C programmer isn t very good at it   One big glaring hole that people tend to forget about is when the program has to block for some sort of IO  such as user input in any GUI program   In these cases  it doesn t really matter what language you use since you are limited by the rate at which data can come in rather than how fast you can process it   In this case  it doesn t matter much if you are using C  Java  C  or even Perl  you just cannot go any faster than the data can come in   The other major thing is that using garbage collection and not using proper pointers allows the virtual machine to make a number of optimizations not available in other languages   For instance  the JVM is capable of moving objects around on the heap to defragment it   This makes future allocations much faster since the next index can simply be used rather than looking it up in a table   Modern JVMs also don t have to actually deallocate memory  instead  they just move the live objects around when they GC and the spent memory from the dead objects is recovered essentially for free   This also brings up an interesting point about C and even more so in C     There is something of a design philosophy of  If you don t need it  you don t pay for it    The problem is that if you do want it  you end up paying through the nose for it   For instance  the vtable implementation in Java tends to be a lot better than C   implementations  so virtual function calls are a lot faster   On the other hand  you have no choice but to use virtual functions in Java and they still cost something  but in programs that use a lot of virtual functions  the reduced cost adds up

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The main factors are that it s a statically-typed language and that s compiled to machine code  Also  since it s a low-level language  it generally doesn t do anything you don t tell it to   These are some other factors that come to mind    Variables are not automatically initialized No bounds checking on arrays Unchecked pointer manipulation No integer overflow checking Statically-typed variables Function calls are static  unless you use function pointers  Compiler writers have had lots of time to improve the optimizing code  Also  people program in C for the purpose of getting the best performance  so there s pressure to optimize the code  Parts of the language specification are implementation-defined  so compilers are free to do things in the most optimal way   Most static-typed languages could be compiled just as fast or faster than C though  especially if they can make assumptions that C can t because of pointer aliasing  etc

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Some C   algorithms are faster than C  and some implementations of algorithms or design patterns in other languages can be faster than C   When people say that C is fast  and then move on to talking about some other language  they are generally using C s performance as a benchmark

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I know plenty of people have said it in a long winded way  but      C is faster because it does less  for you

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I didn t see it already  so I ll say it   C tends to be faster because almost everything else is written in C   Java is built on C  Python is built on C  or Java  or  NET  etc    Perl is  etc   The OS is written in C  the virtual machines are written in C  the compilers are written in C  the interpreters are written in C   Some things are still written in Assembly language  which tends to be even faster   More and more things are being written in something else  which is itself written in C   Each statement that you write in other languages  not Assembly  is typically implemented underneath as several statements in C  which are compiled down to native machine code   Since those other languages tend to exist in order to obtain a higher level of abstraction than C  those extra statements required in C tend to be focused on adding safety  adding complexity  and providing error handling   Those are often good things  but they have a cost  and its names are speed and size   Personally  I have written in literally dozens of languages spanning most of the available spectrum  and I personally have sought the magic that you hint at      How can I have my cake and eat it  too   How can I play with high-level abstractions in my favorite language  then drop down to the nitty gritty of C for speed    After a couple of years of research  my answer is Python  on C    You might want to give it a look   By the way  you can also drop down to Assembly from Python  too  with some minor help from a special library    On the other hand  bad code can be written in any language   Therefore  C  or Assembly  code is not automatically faster   Likewise  some optimization tricks can bring portions of higher-level language code close to the performance level of raw C   But  for most applications  your program spends most of its time waiting on people or hardware  so the difference really does not matter   Enjoy

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The lack of abstraction is what makes C faster  If you write an output statement you know exactly what is happening  If you write an output statement in java it is getting compiled to a class file which then gets run on a virtual machine introducing a layor of abstraction  The lack of object oriented features as a part of the language also increases it s speed do to less code being generated  If you use C as an object oriented language then you are doing all the coding for things such as classes  inharitence  etc  This means rather then make something generalized enough for everyone with the amount of code and the performance penelty that requires you only write what you need to get the job done

[c] Why is C so fast, and why aren't other languages as fast or faster?

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