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Run-Time Routines and .NET Framework Equivalents

Visual Studio .NET 2003

This section lists functions in the C run-time library and the equivalent functions in the .NET Framework.

Note Some listed .NET Framework functions are only approximately equivalent to the corresponding C run-time functions. Also, when using C++, replace the period character (.) with two colons (::).

If the function that you need is not listed, then you can use PInvoke to call the standard C function. For more information, see Platform Invoke Examples.

The main categories of Microsoft run-time library routines are:

Argument Access

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for accessing arguments.

CRT function	.NET Framework equivalent
va_arg, va_end, va_start	System.ParamArrayAttribute class

Buffer Manipulation

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for buffer manipulation.

CRT function	.NET Framework equivalent
_memccpy, memcpy, wmemcpy	System.Buffer.BlockCopy, System.String.Copy
memchr, wmemchr	System.String.CopyTo
memcmp, wmemcmp, _memicmp	System.String.Compare, System.String.Equals
memmove, wmemmove	System.Buffer.BlockCopy
memset, wmemset	System.Buffer.SetByte
_swab	Not applicable

Byte Classification

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for byte classification.

CRT function	.NET Framework equivalent
isleadbyte, _ismbbalnum, _ismbbalpha, _ismbbgraph, _ismbbkalnum, _ismbbkana, _ismbbkprint, _ismbbkpunct, _ismbblead, _ismbbprint, _ismbbpunct, _ismbbtrail, _ismbslead, _ismbstrail, _mbbtype, _mbsbtype	Not applicable, but see System.Globalization.CultureInfo

Character Classification

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for character classification.

CRT function	.NET Framework equivalent
isalnum, iswalnum	System.Char.IsLetterOrDigit
_ismbcalnum	Not applicable
isalpha, iswalpha, _ismbcalpha, __isascii, iswascii	System.Char.IsLetter
iscntrl, iswcntrl	System.Char.IsControl
__iscsym, __iscsymf	System.Char.IsSymbol
isdigit, iswdigit, _ismbcdigit	System.Char.IsDigit
isgraph, iswgraph, _ismbcgraph	Not applicable
islower, iswlower, _ismbclower	System.Char.IsLower
_ismbchira	Not applicable
_ismbckata	Not applicable
_ismbclegal	Not applicable
_ismbcl0, _ismbcl1, _ismbcl2	Not applicable
_ismbcsymbol	Not applicable
isprint, iswprint, _ismbcprint	Not applicable
ispunct, iswpunct, _ismbcpunct	System.Char.IsPunctuation
isspace, iswspace, _ismbcspace	System.Char.IsWhiteSpace
isupper, iswupper, _ismbcupper	System.Char.IsUpper
iswctype	Not applicable
isxdigit, iswxdigit	System.Char.IsNumber
mblen	Not applicable

Data Conversion

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for data conversion.

CRT function	.NET Framework equivalent
abs, _abs64	System.Math.Abs
atof	System.Convert.ToDouble
atoi	System.Convert.ToInt32, System.Convert.ToUInt32
_atoi64	System.Convert.ToInt64, System.Convert.ToUInt64
atol	System.Convert.ToInt64, System.Convert.ToUInt64
_ecvt	System.Convert.ToString
_fcvt	System.Convert.ToString
_gcvt	System.Convert.ToString
_itoa, _i64toa, _ui64toa, _itow, _i64tow, _ui64tow	System.Convert.ToString
labs	System.Math.Abs
_ltoa, _ltow	System.Convert.ToString
_mbbtombc	Not applicable
_mbcjistojms, _mbcjmstojis	Not applicable
_mbctohira, _mbctokata	Not applicable
_mbctombb	Not applicable
mbstowcs	Not applicable
mbtowc	Not applicable
strtod, wcstod	System.Convert.ToDouble
strtol, wcstol	System.Convert.ToInt64
strtoul, wcstoul	System.Convert.ToUInt64
strxfrm, wcsxfrm, __toascii	System.IFormattable.ToString
tolower, towlower, _mbctolower	System.Char.ToLower
_tolower	System.String.ToLower
toupper, towupper, _mbctoupper	System.Char.ToUpper
_toupper	System.String.ToUpper
_ultoa, _ultow	System.Convert.ToString
wcstombs	Not applicable
wctomb	Not applicable
_wtoi	Not applicable
_wtol	Not applicable

Debug

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for debugging.

CRT function	.NET Framework equivalent
_ASSERT, _ASSERTE	System.Diagnostics.Debug.Assert
_CrtCheckMemory	System.Diagnostics.PerformanceCounter
_CrtDbgReport	System.Diagnostics.Debug.Write, System.Diagnostics.Debug.Writeline, System.Diagnostics.Debug.WriteIf, System.Diagnostics.Debug.WriteLineIf
_CrtDoForAllClientObjects	Not applicable
_CrtDumpMemoryLeaks	Not applicable
_CrtIsValidHeapPointer	Not applicable
_CrtIsMemoryBlock	Not applicable
_CrtIsValidPointer	Not applicable
_CrtMemCheckpoint	Not applicable
_CrtMemDifference	Not applicable
_CrtMemDumpAllObjectsSince	Not applicable
_CrtMemDumpStatistics	System.Diagnostics.PerformanceCounter
_CrtSetAllocHook	Not applicable
_CrtSetBreakAlloc	Not applicable
_CrtSetDbgFlag	Not applicable
_CrtSetDumpClient	Not applicable
_CrtSetReportFile	Not applicable
_CrtSetReportHook	Not applicable
_CrtSetReportMode	Not applicable
_RPT[0,1,2,3,4]	Not applicable
_RPTF[0,1,2,3,4]	Not applicable
_calloc_dbg	Not applicable
_expand_dbg	Not applicable
_free_dbg	Not applicable
_malloc_dbg	Not applicable
_msize_dbg	Not applicable
_realloc_dbg	Not applicable

Directory Control

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for directory control.

CRT function	.NET Framework equivalent
_chdir, _wchdir	System.Environment.CurrentDirectory
_chdrive	System.Environment.CurrentDirectory
_getcwd, _wgetcwd	System.Environment.CurrentDirectory
_getdcwd, _wgetdcwd	System.Environment.CurrentDirectory
_getdrive	System.Environment.CurrentDirectory
_mkdir, _wmkdir	System.IO.Directory.CreateDirectory, System.IO.DirectoryInfo.CreateSubdirectory
_rmdir, _wrmdir	System.IO.Directory.Delete
_searchenv, _wsearchenv	Not applicable

Error Handling

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for error handling.

CRT function	.NET Framework equivalent
_ASSERT, _ASSERTE Macros	System.Diagnostics.Debug.Assert
clearerr	Not applicable
_eof	Not applicable
feof	Not applicable
ferror	Not applicable
_RPT, _RPTF Macros	Not applicable

Exception Handling

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for exception handling.

CRT function	.NET Framework equivalent
_set_se_translator	Not applicable
set_terminate	Not applicable
set_unexpected	Not applicable
terminate	Not applicable
unexpected	See System.Exception Class

File-Handling Routines (File Descriptor)

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for file-handling using file descriptors.

CRT function	.NET Framework equivalent
_chsize	System.IO.Stream.SetLength, System.IO.FileStream.SetLength
_filelength, _filelengthi64	System.IO.Stream.SetLength, System.IO.FileStream.SetLength
_fstat, _fstat64, _fstati64	Not applicable
_isatty	System.IO.Stream.CanWrite, System.IO.FileStream.CanWrite
_locking	System.IO.FileStream.Lock
_setmode	See System.IO.BinaryReader Class, System.IO.TextReader Class

File-Handling Routines (Path or File Name)

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for file-handling using paths or file names.

CRT function	.NET Framework equivalent
_access, _waccess	See System.IO.FileAccess enumeration
_chmod, _wchmod	System.IO.File.SetAttributes, System.Security.Permissions.FileIOPermission
_fullpath, _wfullpath	System.IO.File.Create
_get_osfhandle	Not applicable
_makepath, _wmakepath	System.IO.File.Create
_mktemp, _wmktemp	Not applicable
_open_osfhandle	System.IO.FileStream.Handle
remove, _wremove	System.IO.File.Delete
rename, _wrename	System.IO.File.Move
_splitpath, _wsplitpath	Not applicable
_stat, _stat64, _stati64, _wstat, _wstat64, _wstati64	System.IO.File.GetAttributes, System.IO.File.GetCreationTime, System.IO.File.GetLastAccessTime, System.IO.File.GetLastWriteTime
_umask	System.IO.File.SetAttributes
_unlink, _wunlink	System.IO.File.Delete

Floating-Point Support

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for floating-point support.

CRT function	.NET Framework equivalent
abs, _abs64	System.Math.Abs
acos, acosf	System.Math.Acos
asin, asinf	System.Math.Asin
atan, atanf, atan2, atan2f	System.Math.Atan, System.Math.Atan2
atof, _wtof, atoi, _wtoi, _atoi64, _wtoi64, atol, _wtol	System.Convert.ToInt64, System.Convert.ToUInt64, System.Convert.ToSingle, System.Convert.ToDouble
Bessel Functions	Not applicable
_cabs	Not applicable
ceil, ceilf	System.Math.Ceiling
_chgsign	Not applicable
_clear87, _clearfp	Not applicable
_control87, _controlfp	Not applicable
_copysign	Not applicable
cos, cosf, cosh, coshf	System.Math.Cos, System.Math.Cosh
difftime	System.DateTime.Subtract
div	Not applicable
_ecvt	System.Convert.ToString
exp, expf	System.Math.Exp
fabs, fabsf	System.Math.Abs
_fcvt	System.Convert.ToString
_finite	System.Double.IsInfinity
floor, floorf	System.Math.Floor
fmod, fmodf	System.Math.IEEERemainder
_fpclass	System.Double.IsInfinity, System.Double.IsNegativeInfinity, System.Double.IsPositiveInfinity, System.Double.IsNan
_fpieee_flt	Not applicable
frexp	Not applicable
_gcvt	System.Convert.ToString
_hypot, hypotf	Not applicable
_isnan	System.Double.IsNan
labs	System.Math.Abs
ldexp	System.Math.Pow
ldiv	Not applicable
log, logf	System.Math.Log
log10, log10f	System.Math.Log10
_logb	Not applicable
_lrotl, _lrotr	Not applicable
_matherr	Not applicable
__max	System.Math.Max
__min	System.Math.Min
modf, modff	Not applicable
_nextafter	Not applicable
pow, powf	System.Math.Pow
printf, wprintf	System.Console.Write, System.Console.WriteLine
rand	See System.Random Class
_rotl, _rotl64, _rotr_rotr64	Not applicable
_scalb	Not applicable
scanf, wscanf	System.Console.Read, System.Console.ReadLine
sin, sinf, sinh, sinhf	System.Math.Sin, System.Math.Sinh
sqrt, sqrtf	System.Math.Sqrt
srand	See System.Random Class
_status87, _statusfp	Not applicable
strtod, wcstod	System.Convert.ToDouble
tan, tanf, tanh, tanhf	System.Math.Tan, System.Math.Tanh

Input and Output

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for input and output.

CRT function	.NET Framework equivalent
_open, _wopen, fopen, _wfopen, freopen, _wfreopen, _fsopen, _wfsopen	System.IO.File.Open, System.IO.FileStream.FileStream
clearerr	Not applicable
fclose, _fcloseall	System.IO.FileStream.Close, System.IO.Stream.Close, System.IO.BinaryReader.Close, System.IO.BinaryWriter.Close, System.IO.TextReader.Close, System.IO.TextWriter.Close, System.IO.StringReader.Close, System.IO.StringWriter.Close, System.IO.StreamReader.Close, System.IO.StreamWriter.Close
_fdopen, _wfdopen	System.IO.FileStream.FileStream
feof	System.IO.FileStream.Read
ferror	Not applicable
fflush	System.IO.FileStream.Flush
fgetc, fgetwc	System.IO.StreamReader.Read
_fgetchar, _fgetwchar	System.Console.Read
fgetpos	System.IO.FileStream.Position
fgets, fgetws	System.IO.StreamReader.ReadLine, System.IO.TextReader.ReadBlock
_fileno	System.IO.FileStream.Handle
_flushall	System.IO.FileStream.Flush, System.IO.StreamWriter.Flush, System.IO.TextWriter.Flush, System.IO.BinaryWriter.Flush
fopen, _wfopen	System.IO.File.Open
fprintf, fwprintf	System.IO.StreamWriter.Write
fputc, fputwc	System.IO.StreamWriter.Write
_fputchar, _fputwchar	System.Console.Write
fputs, fputws	System.IO.StreamWriter.Write
fread	System.IO.FileStream.Read
freopen, _wfreopen	System.IO.File.Open
fscanf, fwscanf	System.IO.StreamReader.ReadLine; see also Parse methods, such as System.Double.Parse.
fseek	System.IO.FileStream.Position, System.IO.FileStream.Seek
fsetpos	System.IO.FileStream.Position
_fsopen, _wfsopen	Not applicable
ftell	System.IO.FileStream.Position
fwrite	System.IO.FileStream.Write
getc, getwc	System.IO.StreamReader.Read
getchar, getwchar	System.Console.Read
gets, _getws	System.Console.Read
_getw	Not applicable
printf, wprintf	System.Console.Write
putc, putwc	System.IO.StreamWriter.Write
putchar, putwchar	System.Console.Write
puts, _putws	System.Console.Write
_putw	Not applicable
rewind	Not applicable
_rmtmp	Not applicable
scanf, wscanf	System.Console.ReadLine; see also Parse methods, such as System.Double.Parse.
setbuf	Not applicable
_setmaxstdio	Not applicable
setvbuf	Not applicable
_snprintf, _snwprintf	Not applicable
sprintf, swprintf	System.String.Format
sscanf, swscanf	See Parse methods, such as System.Double.Parse
_tempnam, _wtempnam, tmpnam, _wtmpnam	Not applicable
tmpfile	Not applicable
ungetc, ungetwc	Not applicable
vfprintf, vfwprintf	Not applicable
vprintf, vwprintf	System.Console.Write
_vsnprintf, _vsnwprintf	Not applicable
vsprintf, vswprintf	System.String.Format

Internationalization

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for internationalization.

CRT Function	.NET Framework Equivalent
setlocale, _wsetlocale	see System.Globalization.CultureInfo Class

Memory Allocation

Because the common language runtime provides automatic memory management (garbage collection), the .NET Framework has no equivalents for the memory allocation functions in the C run-time library.

CRT function	.NET Framework equivalent
_alloca, calloc, _calloc_dbg, _expand, _expand_dbg, free, _free_dbg, _get_sbh_threshold, _heapadd, _heapchk, _heapmin, _heapset, _heapwalk, malloc, _malloc_dbg, _msize, _msize_dbg, operator new, _query_new_handler, _query_new_mode, realloc, _realloc_dbg, _set_new_handler, _set_new_mode, _set_sbh_threshold	Not applicable

Process and Environment Control

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for process and environment control.

CRT function	.NET Framework equivalent
abort	Not applicable
assert	System.Diagnostics.Debug.Assert
_ASSERT, _ASSERTE Macros	System.Diagnostics.Debug.Assert
atexit	System.Diagnostics.Process.Exited
_beginthread, _beginthreadex	System.Threading.Thread.Start
_cexit, _c_exit	System.Diagnostics.Process.CloseMainWindow
_cwait	System.Diagnostics.Process.WaitForExit
_endthread, _endthreadex	Not applicable
_execl, _wexecl, _execle, _wexecle, _execlp, _wexeclp, _execlpe, _wexeclpe, _execv, _wexecv, _execve, _wexecve, _execvp, _wexecvp, _execvpe, _wexecvpe	See System.Diagnostics.Process Class, System.Diagnostics.ProcessStartInfo Class
exit, _exit	System.Diagnostics.Process.Kill
getenv, _wgetenv	System.Environment.GetEnvironmentVariable
_getpid	System.Diagnostics.Process.Id
longjmp	Not applicable
_onexit	System.Diagnostics.Process.Exited
_pclose	Not applicable
perror, _wperror	Not applicable
_pipe	Not applicable
_popen, _wpopen	Not applicable
_putenv, _wputenv	Not applicable
raise	Not applicable
setjmp	Not applicable
signal	Not applicable
_spawnl, _wspawnl, _spawnle, _wspawnle, _spawnlp, _wspawnlp, _spawnlpe, _wspawnlpe, _spawnv, _wspawnv, _spawnve, _wspawnve, _spawnvp, _wspawnvp, _spawnvpe, _wspawnvpe	See System.Diagnostics.Process Class, System.Diagnostics.ProcessStartInfo Class
system, _wsystem	See System.Diagnostics.ProcessStartInfo Class, System.Diagnostics.Process Class

Searching and Sorting

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for searching and sorting.

CRT function	.NET Framework equivalent
bsearch	System.Collections.ArrayList.BinarySearch
_lfind	System.Collections.ArrayList.Contains
_lsearch	Not applicable
qsort	System.Collections.ArrayList.Sort

String Manipulation

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for string manipulation.

CRT function	.NET Framework equivalent
mbscoll, _mbsicoll, _mbsncoll, _mbsnicoll	System.String.Compare
_mbsdec, _strdec, _wcsdec	Not applicable
_mbsinc, _strinc, _wcsinc	Not applicable
_mbsnbcat	Not applicable
_mbsnbcmp	Not applicable
_mbsnbcnt, _mbsnccnt, _strncnt, _wcsncnt	Not applicable
_mbsnbcpy	Not applicable
_mbsnbicmp	Not applicable
_mbsnbset	Not applicable
_mbsnextc, _strnextc, _wcsnextc	Not applicable
_mbsninc, _strninc, _wcsninc	Not applicable
_mbsspnp, _strspnp, _wcsspnp	Not applicable
sprintf, swprintf	System.String.Format
strcat, wcscat, _mbscat	System.String.Concat
strchr, wcschr, _mbschr	System.String.IndexOf
strcmp, wcscmp, _mbscmp	System.String.CompareOrdinal
strcoll, wcscoll, _stricoll, _wcsicoll, _strncoll, _wcsncoll	System.String.Compare
_strnicoll, _wcsnicoll	System.String.Compare
strcpy, wcscpy, _mbscpy	System.String.Copy
strcspn, wcscspn, _mbscspn	System.String.Substring
_strdup, _wcsdup, _mbsdup	System.String.Clone
strerror, _strerror, _wcserror, __wcserror	System.Exception.Message
strftime, wcsftime	System.Convert.ToString
_stricmp, _wcsicmp, _mbsicmp	System.String.Compare
strlen, wcslen, _mbslen, _mbstrlen	System.String.Length
_strlwr, _wcslwr, _mbslwr	System.String.ToLower
strncat, wcsncat, _mbsncat	System.String.Concat
strncmp, wcsncmp, _mbsncmp	System.String.Compare
strncpy, wcsncpy, _mbsncpy	System.String.Copy
_strnicmp, _wcsnicmp, _mbsnicmp	System.String.Compare
_strnset, _wcsnset, _mbsnset	System.String.Replace
strpbrk, wcspbrk, _mbspbrk	System.String.IndexOfAny
strrchr, wcsrchr, _mbsrchr	System.String.LastIndexOf
_strrev, _wcsrev, _mbsrev	Not applicable
_strset, _wcsset, _mbsset	Not applicable
strspn, wcsspn, _mbsspn	System.String.Substring
strstr, wcsstr, _mbsstr	System.String.IndexOf
strtok, wcstok, _mbstok	Not applicable
_strupr, _wcsupr, _mbsupr	System.String.ToUpper
strxfrm, wcsxfrm	Not applicable
vsprintf, vswprintf	System.String.Format

System Calls

The following .NET Framework equivalents provide similar functionality of the C run-time library functions for system calls.

CRT function	.NET Framework equivalent
_findclose	Not applicable
_findfirst, _findfirst64, _findfirsti64, _wfindfirst, _wfindfirst64, _wfindfirsti64	System.IO.DirectoryInfo.GetFiles
_findnext, _findnext64, _findnexti64, _wfindnext, _wfindnext64, _wfindnexti64	Not applicable

Time Management

The following .NET Framework equivalents provide similar functionality of the C run-time library for time management.

CRT function	.NET Framework equivalent
asctime, _wasctime	System.DateTime.ToLongDateString, System.DateTime.ToLongTimeString, System.DateTime.ToShortDateString, System.DateTime.ToShortTimeString, System.DateTime.ToString
clock	Not applicable
ctime, _ctime64, _wctime, _wctime64	System.DateTime.GetDateTimeFormats, System.DateTime.ToString, System.DateTime.ToLongTimeString, System.DateTime.ToShortTimeString
difftime	System.DateTime.Subtract
_ftime, _ftime64	System.DateTime.Now
_futime, _futime64	System.IO.File.SetLastAccessTime, System.IO.File.SetLastWriteTime, System.IO.File.SetCreationTime
gmtime, _gmtime64	System.DateTime.UtcNow, System.DateTime.ToUniversalTime
localtime, _localtime64	System.DateTime.ToLocalTime
mktime, _mktime64	System.DateTime.DateTime
_strdate, _wstrdate	System.DateTime.Parse
strftime, wcsftime, _strtime, _wstrtime	System.DateTime.ToLongDateString, System.DateTime.ToLongTimeString, System.DateTime.ToShortDateString, System.DateTime.ToShortTimeString, System.DateTime.ToString
time, _time64	Not applicable
_tzset	Not applicable
_utime, _utime64, _wutime, _wutime64	Not applicable