S03 Answer

/* Puzzle S03 -- to lower case */

#include <stdio.h>
#include <stdlib.h>

int isUppercase( int ch )
{
  return ch>='A' && ch<='Z' ;
}

int toLowercase( int ch )
{
  if ( isUppercase( ch ) )
    return ch + 0x20;
  else
    return ch;
}

int main(int argc, char *argv[])
{
  char trials[] = {'a', 'B', 'C', '+', 'z', '0', '?', 0x0D };
  int j, ch;

  for ( j=0; j<sizeof(trials); j++ )
  {
    ch = (unsigned int)trials[j] ; /* char in low order byte */
    printf("%c ", ch );
    printf("to lower case: %c\n", toLowercase(ch) );
  }

  system("PAUSE");
  return 0;
}

Comments: For greater efficiency, you might want toLowercase() to include the code that detects when a character is upper case. Doing this would elimiate one function call.

int toLowercase( int ch )
{
  if ( ch>='A' && ch<='Z' )
    return ch + 0x20;
  else
    return ch;
}

There are several functions that are standard in C environments that convert characters: