tolower(), toupper() — Convert Character Case

Format

#include <ctype.h>

int tolower(int c);   /* Convert c to lowercase if appropriate */
int toupper(int c);   /* Convert c to uppercase if appropriate */

General Description

The tolower() function converts c to a lowercase letter, if possible. Conversely, the toupper() function converts c to an uppercase letter, if possible.

Returned Value

If successful, tolower() and toupper() return the corresponding character, as defined in the IBM-1047 code page, if such a character exists.

If unsuccessful, tolower() and toupper() return the unchanged value c.

Related Information

• ctype.h
• isalnum() to isxdigit() — Test integer value