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The Microsoft run-time library defines the following standard types.
| Type | Description | Declared in | 
|---|---|---|
| clock_t (long) | Stores time values; used by clock. | TIME.H | 
| _complex structure | Stores real and imaginary parts of complex numbers; used by _cabs. | MATH.H | 
| _CRT_ALLOC_HOOK | A type define for the user-defined hook function. Used in _CrtSetAllocHook. | CRTDBG.H | 
| _CRT_DUMP_CLIENT, _CRT_DUMP_CLIENT_M | A type define for a call-back function that will get called in _CrtMemDumpAllObjectsSince. | CRTDBG.H | 
| _CrtMemState structure | Provides information about the current state of the C run-time debug heap. | CRTDBG.H | 
| _CRT_REPORT_HOOK, _CRT_REPORT_HOOKW, _CRT_REPORT_HOOKW_M | A type define for a call-back function that will get called in _CrtDbgReport. The parameters for this function are: report type, output message and the return value from the call-back function. | CRTDBG.H | 
| dev_t, _dev_t short or unsigned integer | Represents device handles. | SYS\TYPES.H | 
| _diskfree_t structure | Contains information about a disk drive. Used by _getdiskfree. | DOS.H and DIRECT.H | 
| div_t, ldiv_t and lldiv_t structures | Store values returned by div, ldiv, and lldiv, respectively. | STDLIB.H | 
| errno_t integer | Used for a function return type or parameter that deals with the error codes of errno. | STDDEF.H, CRTDEFS.H | 
| _exception structure | Stores error information for _matherr. | MATH.H | 
| _EXCEPTION_POINTERS | Contains an exception record. See EXCEPTION_POINTERS for more information. | FPIEEE.H | 
| FILE structure | Stores information about current state of stream; used in all stream I/O operations. | STDIO.H | 
| _finddata_t, _wfinddata_t, _finddata32_t, _wfinddata32_t, _finddatai64_t, _wfinddatai64_t, __finddata64_t, __wfinddata64_t, __finddata32i64_t, __wfinddata32i64_t, __finddata64i32_t, __wfinddata64i32_t structures | Store file-attribute information returned by _findfirst, _wfindfirst and _findnext, _wfindnext. See _find, _wfind Functions for information on structure members. | IO.H, WCHAR.H | 
| _FPIEEE_RECORD structure | Contains information pertaining to IEEE floating-point exception; passed to user-defined trap handler by _fpieee_flt. | FPIEEE.H | 
| fpos_t (long integer, __int64, or structure, depending on the target platform) | Used by fgetpos and fsetpos to record information for uniquely specifying every position within a file. | STDIO.H | 
| _fsize_t (unsigned long integer) | Used to represent the size of a file. | IO.H, WCHAR.H | 
| _HEAPINFO structure | Contains information about next heap entry for _heapwalk. | MALLOC.H | 
| _HFILE (void *) | An operating system file handle. | CRTDBG.H | 
| imaxdiv_t | The type of value that's returned by the imaxdiv function, containing both the quotient and the remainder. | inttypes.h | 
| ino_t, _ino_t (unsigned short) | For returning status information. | WCHAR.H | 
| intmax_t | A signed integer type capable of representing any value of any signed integer type. | stdint.h | 
| intptr_t (long integer or __int64, depending on the target platform) | Stores a pointer (or HANDLE) on both Win32 and Win64 platforms. | STDDEF.H and other include files | 
| jmp_buf array | Used by setjmp and longjmp to save and restore program environment. | SETJMP.H | 
| lconv structure | Contains formatting rules for numeric values in different countries/regions. Used by localeconv. | LOCALE.H | 
| _LDOUBLE, _LONGDOUBLE, _LDBL12 (long double or an unsigned char array) | Use to represent a long double value. | STDLIB.H | 
| _locale_t structure | Stores current locale values; used in all locale specific C run-time libraries. | CRTDEF.H | 
| mbstate_t | Tracks the state of a multibyte character conversion. | WCHAR.H | 
| off_t, _off_t long integer | Represents file-offset value. | WCHAR.H, SYS\TYPES.H | 
| _onexit_t, _onexit_m_t pointer | Returned by _onexit, _onexit_m. | STDLIB.H | 
| _PNH pointer to function | Type of argument to _set_new_handler. | NEW.H | 
| ptrdiff_t (long integer or __int64, depending on the target platform) | Result of subtraction of two pointers. | CRTDEFS.H | 
| _purecall_handler, _purecall_handler_m | A type define for a call-back function that is called when a pure virtual function is called. Used by _set_purecall_handler. A _purecall_handler function should have a void return type. | STDLIB.H | 
| _RTC_error_fn type define | A type define for a function that will handle run-time error checks. Used in _RTC_SetErrorFunc. | RTCAPI.H | 
| _RTC_error_fnW type define | A type define for a function that will handle run-time error checks. Used in _RTC_SetErrorFuncW. | RTCAPI.H | 
| _RTC_ErrorNumber enumeration | Defines error conditions for _RTC_GetErrDesc and _RTC_SetErrorType. | RTCAPI.H | 
| _se_translator_function | A type define for a call-back function that translates an exception. The first parameter is the exception code and the second parameter is the exception record. Used by _set_se_translator. | EH.H | 
| sig_atomic_t integer | Type of object that can be modified as atomic entity, even in presence of asynchronous interrupts; used with signal. | SIGNAL.H | 
| size_t (unsigned __int64 or unsigned integer, depending on the target platform) | Result of sizeof operator. | CRTDEFS.H and other include files | 
| _stat structure | Contains file-status information returned by _stat and _fstat. | SYS\STAT.H | 
| __stat64 structure | Contains file-status information returned by _fstat64 and _stat64, and _wstat64. | SYS\STAT.H | 
| _stati64 structure | Contains file-status information returned by _fstati64, _stati64, and _wstati64. | SYS\STAT.H | 
| terminate_function type define | A type define for a call-back function that is called when terminate is called. Used by set_terminate. | EH.H | 
| time_t (__int64 or long integer) | Represents time values in mktime, time, ctime, _ctime32, _ctime64, _wctime, _wctime32, _wctime64, ctime_s, _ctime32_s, _ctime64_s, _wctime_s, _wctime32_s, _wctime64_s, ctime, _ctime32, _ctime64, _wctime, _wctime32, _wctime64 and gmtime, _gmtime32, _gmtime64. The number of seconds since January 1, 1970, 0:00 UTC. If _USE_32BIT_TIME_T is defined, time_t is a long integer. If not defined, it is a 64-bit integer. | TIME.H, SYS\STAT.H, SYS\TIMEB.H | 
| __time32_t (long integer) | Represents time values in mktime, _mktime32, _mktime64, ctime, _ctime32, _ctime64, _wctime, _wctime32, _wctime64, ctime_s, _ctime32_s, _ctime64_s, _wctime_s, _wctime32_s, _wctime64_s, gmtime, _gmtime32, _gmtime64 and localtime, _localtime32, _localtime64. | CRTDEFS.H, SYS\STAT.H, SYS\TIMEB.H | 
| __time64_t (__int64) | Represents time values in mktime, _mktime32, _mktime64, _ctime64, _wctime64, ctime_s, _ctime32_s, _ctime64_s, _wctime_s, _wctime32_s, _wctime64_s, _gmtime64, _localtime64 and _time64. | TIME.H, SYS\STAT.H, SYS\TIMEB.H | 
| _timeb structure | Used by _ftime and _ftime_s, _ftime32_s, _ftime64_s to store current system time. | SYS\TIMEB.H | 
| __timeb32 structure | Used by _ftime, _ftime32, _ftime64 and _ftime_s, _ftime32_s, _ftime64_s to store current system time. | SYS\TIMEB.H | 
| __timeb64 structure | Used by _ftime64 and _ftime_s, _ftime32_s, _ftime64_s to store current system time. | SYS\TIMEB.H | 
| tm structure | Used by asctime, _wasctime, asctime_s, _wasctime_s, gmtime, _gmtime32, _gmtime64, gmtime_s, _gmtime32_s, _gmtime64_s, localtime, _localtime32, _localtime64, localtime_s, _localtime32_s, _localtime64_s, mktime, _mktime32, _mktime64 and strftime, wcsftime, _strftime_l, _wcsftime_l to store and retrieve time information. | TIME.H | 
| uintmax_t | An unsigned integer type capable of representing any value of any unsigned integer type. | stdint.h | 
| uintptr_t (long integer or __int64, depending on the target platform) | An unsigned integer or unsigned __int64 version of intptr_t. | STDDEF.H and other include files | 
| unexpected_function | A type define for a call-back function that is called when unexpected is called. Used by set_unexpected. | EH.H | 
| _utimbuf structure | Stores file access and modification times used by _utime, _wutime and _futime, _futime32, _futime64 to change file-modification dates. | SYS\UTIME.H | 
| _utimbuf32 structure | Stores file access and modification times used by _utime, _utime32, _utime64, _wutime, _wutime32, _wutime64 and _futime, _futime32, _futime64 to change file-modification dates. | SYS\UTIME.H | 
| __utimbuf64 structure | Used by _utime64, _wutime64 and _futime64 to store the current time. | SYS\UTIME.H | 
| va_list structure | Used to hold information needed by va_arg and va_end macros. Called function declares variable of type va_list that can be passed as argument to another function. | STDARG.H, CRTDEFS.H | 
| wchar_t wide character | Useful for writing portable programs for international markets. | STDDEF.H, STDLIB.H, CRTDEFS.H, SYS\STAT.H | 
| wctrans_t integer | Represents locale-specific character mappings. | WCTYPE.H | 
| wctype_t integer | Can represent all characters of any language character set. | WCHAR.H, CRTDEFS.H | 
| wint_t integer | Type of data object that can hold any wide character or wide end-of-file value. | WCHAR.H, CRTDEFS.H |