tolower - toupper - Convert Character Case

Syntax

#include <ctype.h>
int tolower(int C);
int toupper(int c);

tolower converts the uppercase letter C to the corresponding lowercase letter.

toupper converts the lowercase letter c to the corresponding uppercase letter.

The character mapping is determined by the LC_CTYPE category of the current locale.

Note: toupper and tolower can only be used for single-byte characters. towupper and towlower should be used for case conversion of wide characters that are equivalent to both single-byte and double-byte characters.

Both functions return the converted character. If the character c does not have a corresponding lowercase or uppercase character, the functions return c unchanged.

This example uses toupper and tolower to modify characters between code 0 and code 7f.

#include <stdio.h>
#include <ctype.h>

int main(void)
{
   int ch;

   /* print hex values of characters */
   for (ch = 0; ch <= 0x7f; ch++) {
      printf("toupper=%#04x\n", toupper(ch));
      printf("tolower=%#04x\n", tolower(ch));
      putchar('\n');
   }
   return 0;
}

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