difference between stdint.h and inttypes.h

Question

What is the difference between stdint.h and inttypes.h?

If none of them is used, uint64_t is not recognized but with either of them it is a defined type.

Answer 1

See the wikipedia article for inttypes.h.

Use stdint.h for a minimal set of definitions; use inttypes.h if you also need portable support for these in printf, scanf, et al.

Answer 2

stdint.h

Including this file is the "minimum requirement" if you want to work with the specified-width integer types of C99 (i.e. "int32_t", "uint16_t" etc.). If you include this file, you will get the definitions of these types, so that you will be able to use these types in declarations of variables and functions and do operations with these datatypes.

inttypes.h

If you include this file, you will get everything that stdint.h provides (because inttypes.h includes stdint.h), but you will also get facilities for doing printf and scanf (and "fprintf, "fscanf", and so on.) with these types in a portable way. For example, you will get the "PRIu16" macro so that you can printf an uint16_t integer like this:

#include <stdio.h>
#include <inttypes.h>
int main (int argc, char *argv[]) {

    // Only requires stdint.h to compile:
    uint16_t myvar = 65535;

    // Requires inttypes.h to compile:
    printf("myvar=%" PRIu16 "\n", myvar);  
}