(libc.info)Case Conversion


Case Conversion
===============

   This section explains the library functions for performing
conversions such as case mappings on characters.  For example, `toupper'
converts any character to upper case if possible.  If the character
can't be converted, `toupper' returns it unchanged.

   These functions take one argument of type `int', which is the
character to convert, and return the converted character as an `int'.
If the conversion is not applicable to the argument given, the argument
is returned unchanged.

   *Compatibility Note:* In pre-ISO C dialects, instead of returning
the argument unchanged, these functions may fail when the argument is
not suitable for the conversion.  Thus for portability, you may need to
write `islower(c) ? toupper(c) : c' rather than just `toupper(c)'.

   These functions are declared in the header file `ctype.h'.

 - Function: int tolower (int C)
     If C is an upper-case letter, `tolower' returns the corresponding
     lower-case letter.  If C is not an upper-case letter, C is
     returned unchanged.

 - Function: int toupper (int C)
     If C is a lower-case letter, `toupper' returns the corresponding
     upper-case letter.  Otherwise C is returned unchanged.

 - Function: int toascii (int C)
     This function converts C to a 7-bit `unsigned char' value that
     fits into the US/UK ASCII character set, by clearing the high-order
     bits.  This function is a BSD extension and is also an SVID
     extension.

 - Function: int _tolower (int C)
     This is identical to `tolower', and is provided for compatibility
     with the SVID.  Note: SVID.

 - Function: int _toupper (int C)
     This is identical to `toupper', and is provided for compatibility
     with the SVID.


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