These routines convert data from one form to another. Generally these routines execute faster than conversions you might write. Each routine that begins with a to prefix is implemented as a function and as a macro. See Choosing Between Functions and Macros for information about choosing an implementation.
Data-Conversion Routines
| Routine | Use |
| abs | Find absolute value of integer |
| atof | Convert string to float |
| atoi, _atoi64 | Convert string to int |
| atol | Convert string to long |
| _ecvt | Convert double to string of specified length |
| _fcvt | Convert double to string with specified number of digits following decimal point |
| _gcvt | Convert double number to string; store string in buffer |
| _itoa, _i64toa, _itow, _i64tow | Convert int to string |
| labs | Find absolute value of long integer |
| _ltoa, _ltow | Convert long to string |
| _mbbtombc | Convert 1-byte multibyte character to corresponding 2-byte multibyte character |
| _mbcjistojms | Convert Japan Industry Standard (JIS) character to Japan Microsoft (JMS) character |
| _mbcjmstojis | Convert JMS character to JIS character |
| _mbctohira | Convert multibyte character to 1-byte hiragana code |
| _mbctokata | Convert multibyte character to 1-byte katakana code |
| _mbctombb | Convert 2-byte multibyte character to corresponding 1-byte multibyte character |
| mbstowcs | Convert sequence of multibyte characters to corresponding sequence of wide characters |
| mbtowc | Convert multibyte character to corresponding wide character |
| strtod, wcstod | Convert string to double |
| strtol, wcstol | Convert string to long integer |
| strtoul, wcstoul | Convert string to unsigned long integer |
| strxfrm, wcsxfrm | Transform string into collated form based on locale-specific information |
| __toascii | Convert character to ASCII code |
| tolower, towlower, _mbctolower | Test character and convert to lowercase if currently uppercase |
| _tolower | Convert character to lowercase unconditionally |
| toupper, towupper, _mbctoupper | Test character and convert to uppercase if currently lowercase |
| _toupper | Convert character to uppercase unconditionally |
| _ultoa, _ultow | Convert unsigned long to string |
| wcstombs | Convert sequence of wide characters to corresponding sequence of multibyte characters |
| wctomb | Convert wide character to corresponding multibyte character |
| _wtoi | Convert wide-character string to int |
| _wtol | Convert wide-character string to long |