Sets a new multibyte code page.

int _setmbcp(
   int codepage 


  • codepage
    New code page setting for locale-independent multibyte routines.

Return Value

Returns 0 if the code page is set successfully. If an invalid code page value is supplied for codepage, returns –1 and the code page setting is unchanged. Sets errno to EINVAL if a memory allocation failure occurs.


The _setmbcp function specifies a new multibyte code page. By default, the run-time system automatically sets the multibyte code page to the system-default ANSI code page. The multibyte code page setting affects all multibyte routines that are not locale dependent. However, it is possible to instruct _setmbcp to use the code page defined for the current locale (see the following list of manifest constants and associated behavior results). For a list of the multibyte routines that are dependent on the locale code page rather than the multibyte code page, see Interpretation of Multibyte-Character Sequences.

The multibyte code page also affects multibyte-character processing by the following run-time library routines:

_exec functions




_spawn functions





In addition, all run-time library routines that receive multibyte-character argv or envp program arguments as parameters (such as the _exec and _spawn families) process these strings according to the multibyte code page. Therefore, these routines are also affected by a call to _setmbcp that changes the multibyte code page.

The codepage argument can be set to any of the following values:

  • _MB_CP_ANSI   Use ANSI code page obtained from operating system at program startup.

  • _MB_CP_LOCALE   Use the current locale's code page obtained from a previous call to setlocale.

  • _MB_CP_OEM   Use OEM code page obtained from operating system at program startup.

  • _MB_CP_SBCS   Use single-byte code page. When the code page is set to _MB_CP_SBCS, a routine such as _ismbblead always returns false.

  • Any other valid code page value, regardless of whether the value is an ANSI, OEM, or other operating-system-supported code page (except UTF-7 and UTF-8, which are not supported).



Required header



For more compatibility information, see Compatibility in the Introduction.

See Also



setlocale, _wsetlocale