CODE EXAMPLE FOR C

function that changes all lowercase letters of a string to uppercase.

char *string_toupper(char *s)
{
  	int i;
     while( s[i] != '' ) 
     {
        // if character is in lowercase
        // then subtract 32 
        if( s[i] >= 'a' && s[i] <= 'z' )
        {
           s[i] = s[i] - 32;
        }

        // increase iterator variable
        i++;
     }
     return (s);
 }