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inttypes.h - fixed size integer types
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, Sec‐
tion 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 fol‐
Structure type that is the type of the value returned by the
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 inte‐
ger 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 exam‐
ple, 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 cor‐
responding 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.
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);
uintmax_t i = UINTMAX_MAX; // This type always exists.
wprintf(L"The largest integer value is %020"
PRIxMAX "\n", i);
The following sections are informative.
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 type
def, integer types of various sizes. Implementations are free to type
def them as ISO C standard integer types or extensions that they sup‐
port. Consistent use of this header will greatly increase the portabil‐
ity of applications across platforms.
The ISO/IEC 9899:1990 standard specified that the language should sup‐
port 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, respec‐
tively. 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 stan‐
dard integer promotion rule can produce silent changes unexpectedly.
The need for defining an extended integer type increased with the
introduction of 64-bit systems.
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.
The System Interfaces volume of IEEE Std 1003.1-2001, imaxdiv()
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .