Does C have a string type

Question

I have recently started programming in C  coming from Java and Python  Now  in my book I have noticed that to make a  Hello World  program  the syntax is something like this   char message 10  strcpy message   Hello  world    printf   s n   message     Now  this example is using a char array and I wondered - what happened to strings  Why can t I simply use one of those  Maybe there is a different way to do this

User · Answer

To note it in the languages you mentioned:

Java:

String str = new String("Hello");

Python:

str = "Hello"

Both Java and Python have the concept of a "string", C does not have the concept of a "string". C has character arrays which can come in "read only" or manipulatable.

C:

char * str = "Hello";  // the string "Hello\0" is pointed to by the character pointer
                       // str. This "string" can not be modified (read only)

or

char str[] = "Hello";  // the characters: 'H''e''l''l''o''\0' have been copied to the 
                       // array str. You can change them via: str[x] = 't'

A character array is a sequence of contiguous characters with a unique sentinel character at the end (normally a NULL terminator '\0'). Note that the sentinel character is auto-magically appended for you in the cases above.

User · Answer

In C  a string simply is an array of characters  ending with a null byte  So a char  is often pronounced  string   when you re reading C code

User · Answer

C does not support a first class string type   C   has std  string

User · Answer

First  you don t need to do all that  In particular  the strcpy is redundant - you don t need to copy a string just to printf it  Your message can be defined with that string in place   Second  you ve not allowed enough space for that  Hello  World   string  message needs to be at least 14 characters  allowing the extra one for the null terminator    On the why  though  it s history  In assembler  there are no strings  only bytes  words etc  Pascal had strings  but there were problems with static typing because of that - string 20  was a different type that string 40   There were languages even in the early days that avoided this issue  but that caused indirection and dynamic allocation overheads which were much more of an efficiency problem back then   C simply chose to avoid the overheads and stay very low level  Strings are character arrays  Arrays are very closely related to pointers that point to their first item  When array types  decay  to pointer types  the buffer-size information is lost from the static type  so you don t get the old Pascal string issues   In C    there s the std  string class which avoids a lot of these issues - and has the dynamic allocation overheads  but these days we usually don t care about that  And in any case  std  string is a library class - there s C-style character-array handling underneath

User · Answer

C does not and never has had a native string type  By convention  the language uses arrays of char terminated with a null char  i e   with   0   Functions and macros in the language s standard libraries provide support for the null-terminated character arrays  e g   strlen iterates over an array of char until it encounters a   0  character and strcpy copies from the source string until it encounters a   0    The use of null-terminated strings in C reflects the fact that C was intended to be only a little more high-level than assembly language  Zero-terminated strings were already directly supported at that time in assembly language for the PDP-10 and PDP-11   It is worth noting that this property of C strings leads to quite a few nasty buffer overrun bugs  including serious security flaws  For example  if you forget to null-terminate a character string passed as the source argument to strcpy  the function will keep copying sequential bytes from whatever happens to be in memory past the end of the source string until it happens to encounter a 0  potentially overwriting whatever valuable information follows the destination string s location in memory   In your code example  the string literal  Hello  world   will be compiled into a 14-byte long array of char  The first 13 bytes will hold the letters  comma  space  and exclamation mark and the final byte will hold the null-terminator character   0   automatically added for you by the compiler  If you were to access the array s last element  you would find it equal to 0  E g    const char foo      Hello  world    assert foo 12           assert foo 13       0      However  in your example  message is only 10 bytes long  strcpy is going to write all 14 bytes  including the null-terminator  into memory starting at the address of message  The first 10 bytes will be written into the memory allocated on the stack for message and the remaining four bytes will simply be written on to the end of the stack  The consequence of writing those four extra bytes onto the stack is hard to predict in this case  in this simple example  it might not hurt a thing   but in real-world code it usually leads to corrupted data or memory access violation errors

User · Answer

There is no string type in C  You have to use char arrays    By the way your code will not work  because the size of the array should allow for the whole array to fit in plus one additional zero terminating character

User · Answer

C does not have its own String data type like Java    Only we can declare String datatype in C using character array or character pointer For example     char message 10     or   char  message    But you need to declare at least         char message 14      to copy  Hello  world   into message variable    13   length of the  Hello  world   1   for   0  null character that identifies end of the string

[c] Does C have a string type?

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