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_itoa, _i64toa, _ui64toa, _itow, _i64tow, _ui64tow

Converts an integer to a string. More secure versions of these functions are available; see _itoa_s, _i64toa_s, _ui64toa_s, _itow_s, _i64tow_s, _ui64tow_s.

char *_itoa(
   int value,
   char *str,
   int radix 
);
char *_i64toa(
   __int64 value,
   char *str,
   int radix 
);
char * _ui64toa(
   unsigned _int64 value,
   char *str,
   int radix 
);
wchar_t * _itow(
   int value,
   wchar_t *str,
   int radix 
);
wchar_t * _i64tow(
   __int64 value,
   wchar_t *str,
   int radix 
);
wchar_t * _ui64tow(
   unsigned __int64 value,
   wchar_t *str,
   int radix 
);
template <size_t size>
char *_itoa(
   int value,
   char (&str)[size],
   int radix 
); // C++ only
template <size_t size>
char *_i64toa(
   __int64 value,
   char (&str)[size],
   int radix 
); // C++ only
template <size_t size>
char * _ui64toa(
   unsigned _int64 value,
   char (&str)[size],
   int radix 
); // C++ only
template <size_t size>
wchar_t * _itow(
   int value,
   wchar_t (&str)[size],
   int radix 
); // C++ only
template <size_t size>
wchar_t * _i64tow(
   __int64 value,
   wchar_t (&str)[size],
   int radix 
); // C++ only
template <size_t size>
wchar_t * _ui64tow(
   unsigned __int64 value,
   wchar_t (&str)[size],
   int radix 
); // C++ only
value

Number to be converted.

str

String result.

radix

Base of value; which must be in the range 2–36.

Each of these functions returns a pointer to str. There is no error return.

The _itoa, _i64toa, and _ui64toa functions convert the digits of the given value argument to a null-terminated character string and stores the result (up to 33 characters for _itoa and 65 for _i64toa and _ui64toa) in str. If radix equals 10 and value is negative, the first character of the stored string is the minus sign ( ). _itow, _i64tow, and _ui64tow are wide-character versions of _itoa, _i64toa, and _ui64toa, respectively.

Security noteSecurity Note:

To prevent buffer overruns, ensure that the str buffer is large enough to hold the converted digits plus the trailing null-character and a sign character.

In C++, these functions have template overloads that invoke the newer, secure counterparts of these functions. For more information, see Secure Template Overloads.

Generic-Text Routine Mappings

Tchar.h routine

_UNICODE and _MBCS not defined

_MBCS defined

_UNICODE defined

_itot

_itoa

_itoa

_itow

_i64tot

_i64toa

_i64toa

_i64tow

_ui64tot

_ui64toa

_ui64toa

_ui64tow

Routine

Required header

_itoa

<stdlib.h>

_i64toa

<stdlib.h>

_ui64toa

<stdlib.h>

_itow

<stdlib.h>

_i64tow

<stdlib.h>

_ui64tow

<stdlib.h>

For more compatibility information, see Compatibility in the Introduction.

// crt_itoa.c
// compile with: /W3
// This program makes use of the _itoa functions
// in various examples.

#include <string.h>
#include <stdlib.h>

int main( void )
{
   char buffer[65];
   int r;
   for( r=10; r>=2; --r )
   {
     _itoa( -1, buffer, r ); // C4996
     // Note: _itoa is deprecated; consider using _itoa_s instead
     printf( "base %d: %s (%d chars)\n", r, buffer, strnlen(buffer, _countof(buffer)) );
   }
   printf( "\n" );
   for( r=10; r>=2; --r )
   {
     _i64toa( -1L, buffer, r ); // C4996
     // Note: _i64toa is deprecated; consider using _i64toa_s
     printf( "base %d: %s (%d chars)\n", r, buffer, strnlen(buffer, _countof(buffer)) );
   }
   printf( "\n" );
   for( r=10; r>=2; --r )
   {
     _ui64toa( 0xffffffffffffffffL, buffer, r ); // C4996
     // Note: _ui64toa is deprecated; consider using _ui64toa
     printf( "base %d: %s (%d chars)\n", r, buffer, strnlen(buffer, _countof(buffer)) );
   }
}
base 10: -1 (2 chars) base 9: 12068657453 (11 chars) base 8: 37777777777 (11 chars) base 7: 211301422353 (12 chars) base 6: 1550104015503 (13 chars) base 5: 32244002423140 (14 chars) base 4: 3333333333333333 (16 chars) base 3: 102002022201221111210 (21 chars) base 2: 11111111111111111111111111111111 (32 chars) base 10: -1 (2 chars) base 9: 145808576354216723756 (21 chars) base 8: 1777777777777777777777 (22 chars) base 7: 45012021522523134134601 (23 chars) base 6: 3520522010102100444244423 (25 chars) base 5: 2214220303114400424121122430 (28 chars) base 4: 33333333333333333333333333333333 (32 chars) base 3: 11112220022122120101211020120210210211220 (41 chars) base 2: 1111111111111111111111111111111111111111111111111111111111111111 (64 chars) base 10: 18446744073709551615 (20 chars) base 9: 145808576354216723756 (21 chars) base 8: 1777777777777777777777 (22 chars) base 7: 45012021522523134134601 (23 chars) base 6: 3520522010102100444244423 (25 chars) base 5: 2214220303114400424121122430 (28 chars) base 4: 33333333333333333333333333333333 (32 chars) base 3: 11112220022122120101211020120210210211220 (41 chars) base 2: 1111111111111111111111111111111111111111111111111111111111111111 (64 chars)
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