What is the difference between long long long long int and long long int in C

Question

I am transitioning from Java to C   and have some questions about the long data type  In Java  to hold an integer greater than 232  you would simply write long x   However  in C    it seems that long is both a data type and a modifier    There seems to be several ways to use long   long x  long long x  long int x  long long int x    Also  it seems there are things such as   long double x    and so on   What is the difference between all of these various data types  and do they all have the same purpose

User · Answer

long is equivalent to long int  just as short is equivalent to short int  A long int is a signed integral type that is at least 32 bits  while a long long or long long int is a signed integral type is at least 64 bits   This doesn t necessarily mean that a long long is wider than a long  Many platforms   ABIs use the LP64 model - where long  and pointers  are 64 bits wide  Win64 uses the LLP64  where long is still 32 bits  and long long  and pointers  are 64 bits wide   There s a good summary of 64-bit data models here   long double doesn t guarantee much other than it will be at least as wide as a double

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While in Java a long is always 64 bits  in C   this depends on computer architecture and operating system  For example  a long is 64 bits on Linux and 32 bits on Windows  this was done to keep backwards-compatability  allowing 32-bit programs to compile on 64-bit Windows without any changes    It is considered good C   style to avoid short int long     and instead use   std  int8 t     exactly  8 bits std  int16 t    exactly 16 bits std  int32 t    exactly 32 bits std  int64 t    exactly 64 bits  std  size t     can hold all possible object sizes  used for indexing   These  int  t  can be used after including the  lt cstdint gt  header  size t is in  lt stdlib h gt

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Long and long int are at least 32 bits   long long and long long int are at least 64 bits  You must be using a c99 compiler or better   long doubles are a bit odd  Look them up on Wikipedia for details

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long and long int are identical  So are long long and long long int  In both cases  the int is optional   As to the difference between the two sets  the C   standard mandates minimum ranges for each  and that long long is at least as wide as long   The controlling parts of the standard  C  11  but this has been around for a long time  are  for one  3 9 1 Fundamental types  section 2  a later section gives similar rules for the unsigned integral types       There are five standard signed integer types   signed char  short int  int  long int  and long long int  In this list  each type provides at least as much storage as those preceding it in the list    There s also a table 9 in 7 1 6 2 Simple type specifiers  which shows the  mappings  of the specifiers to actual types  showing that the int is optional   a section of which is shown below   Specifier s          Type -------------    ------------- long long int    long long int long long        long long int long int         long int long             long int   Note the distinction there between the specifier and the type  The specifier is how you tell the compiler what the type is but you can use different specifiers to end up at the same type   Hence long on its own is neither a type nor a modifier as your question posits  it s simply a specifier for the long int type  Ditto for long long being a specifier for the long long int type   Although the C   standard itself doesn t specify the minimum ranges of integral types  it does cite C99  in 1 2 Normative references  as applying  Hence the minimal ranges as set out in C99 5 2 4 2 1 Sizes of integer types  lt limits h gt  are applicable     In terms of long double  that s actually a floating point value rather than an integer  Similarly to the integral types  it s required to have at least as much precision as a double and to provide a superset of values over that type  meaning at least those values  not necessarily more values

User · Answer

Historically  in early C times  when processors had 8 or 16 bit wordlength intwas identical to todays short 16 bit   In a certain sense  int is a more abstract data type thanchar short longorlong long  as you cannot be sure about the bitwidth    When definingint n you could translate this with  give me the best compromise of bitwidth and speed on this machine for n   Maybe in the future you should expect compilers to translateintto be 64 bit  So when you want your variable to have 32 bits and not more  better use an explicitlongas data type    Edit   include  lt stdint h gt  seems to be the proper way to ensure bitwidths using the int   t types  though it s not yet part of the standard

User · Answer

This looks confusing because you are taking long as a datatype itself   long is nothing but just the shorthand for long int when you are using it alone   long is a modifier  you can use it with double also as long double   long    long int   Both of them take 4 bytes

[c++] What is the difference between "long", "long long", "long int", and "long long int" in C++?

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