NAME

inttypes.h - fixed size integer types

SYNOPSIS

#include <inttypes.h>

DESCRIPTION

^[CX] Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the System Interfaces volume of IEEE Std 1003.1-2001, Section 2.2, The Compilation Environment) to enable the visibility of these symbols in this header.

The <inttypes.h> header shall include the <stdint.h> header.

The <inttypes.h> header shall include a definition of at least the following type:

imaxdiv_t

Structure type that is the type of the value returned by the imaxdiv() function.

The following macros shall be defined. Each expands to a character string literal containing a conversion specifier, possibly modified by a length modifier, suitable for use within the format argument of a formatted input/output function when converting the corresponding integer type. These macros have the general form of PRI (character string literals for the fprintf() and fwprintf() family of functions) or SCN (character string literals for the fscanf() and fwscanf() family of functions), followed by the conversion specifier, followed by a name corresponding to a similar type name in <stdint.h>. In these names, N represents the width of the type as described in <stdint.h>. For example, PRIdFAST32 can be used in a format string to print the value of an integer of type int_fast32_t.

The fprintf() macros for signed integers are:

PRIdN	PRIdLEASTN	PRIdFASTN	PRIdMAX	PRIdPTR
PRIiN	PRIiLEASTN	PRIiFASTN	PRIiMAX	PRIiPTR

The fprintf() macros for unsigned integers are:

PRIoN	PRIoLEASTN	PRIoFASTN	PRIoMAX	PRIoPTR
PRIuN	PRIuLEASTN	PRIuFASTN	PRIuMAX	PRIuPTR
PRIxN	PRIxLEASTN	PRIxFASTN	PRIxMAX	PRIxPTR
PRIXN	PRIXLEASTN	PRIXFASTN	PRIXMAX	PRIXPTR

The fscanf() macros for signed integers are:

SCNdN	SCNdLEASTN	SCNdFASTN	SCNdMAX	SCNdPTR
SCNiN	SCNiLEASTN	SCNiFASTN	SCNiMAX	SCNiPTR

The fscanf() macros for unsigned integers are:

SCNoN	SCNoLEASTN	SCNoFASTN	SCNoMAX	SCNoPTR
SCNuN	SCNuLEASTN	SCNuFASTN	SCNuMAX	SCNuPTR
SCNxN	SCNxLEASTN	SCNxFASTN	SCNxMAX	SCNxPTR

For each type that the implementation provides in <stdint.h>, the corresponding fprintf() and fwprintf() macros shall be defined and the corresponding fscanf() and fwscanf() macros shall be defined unless the implementation does not have a suitable modifier for the type.

The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.

intmax_t  imaxabs(intmax_t);
imaxdiv_t imaxdiv(intmax_t, intmax_t);
intmax_t  strtoimax(const char *restrict, char **restrict, int);
uintmax_t strtoumax(const char *restrict, char **restrict, int);
intmax_t  wcstoimax(const wchar_t *restrict, wchar_t **restrict, int);
uintmax_t wcstoumax(const wchar_t *restrict, wchar_t **restrict, int);

EXAMPLES

#include <inttypes.h>
#include <wchar.h>
int main(void)
{
    uintmax_t i = UINTMAX_MAX; // This type always exists.
    wprintf(L"The largest integer value is %020"
        PRIxMAX "\n", i);
    return 0;
}

APPLICATION USAGE

The purpose of <inttypes.h> is to provide a set of integer types whose definitions are consistent across machines and independent of operating systems and other implementation idiosyncrasies. It defines, via typedef, integer types of various sizes. Implementations are free to typedef them as ISO C standard integer types or extensions that they support. Consistent use of this header will greatly increase the portability of applications across platforms.

RATIONALE

The ISO/IEC 9899:1990 standard specified that the language should support four signed and unsigned integer data types- char, short, int, and long- but placed very little requirement on their size other than that int and short be at least 16 bits and long be at least as long as int and not smaller than 32 bits. For 16-bit systems, most implementations assigned 8, 16, 16, and 32 bits to char, short, int, and long, respectively. For 32-bit systems, the common practice has been to assign 8, 16, 32, and 32 bits to these types. This difference in int size can create some problems for users who migrate from one system to another which assigns different sizes to integer types, because the ISO C standard integer promotion rule can produce silent changes unexpectedly. The need for defining an extended integer type increased with the introduction of 64-bit systems.

FUTURE DIRECTIONS

Macro names beginning with PRI or SCN followed by any lowercase letter or 'X' may be added to the macros defined in the <inttypes.h> header.

SEE ALSO

The System Interfaces volume of IEEE Std 1003.1-2001, imaxdiv()

CHANGE HISTORY

First released in Issue 5.

Issue 6

The Open Group Base Resolution bwg97-006 is applied.

This reference page is updated to align with the ISO/IEC 9899:1999 standard.