Accessing Characters in a String

They all do the same thing, but some of the methods are slower.

The Program

/*********************************************
**  File: quicker.c
**  Author: S. Bogar
**  Date:   8/8/96
**  Modified: 9/26/05
**  Section: 101
**  EMail: bogar@cs.umbc.edu
**
**    Quicker ways to access the characters in a string.
**********************************************
/
#include <stdio.h>
#include <string.h>
#include <ctype.h>

int main() 
{
   int i, length ;   
   char c, str[31] = "this line is all in upper case" ;

   /* This is a fast way */
   printf("Method 1: ") ;
   for(i = 0; str[i] != '\0'; i++) 
   {
      c = str[i] ;
      c = toupper(c) ;
      printf("%c", c) ;
   }
   printf("\n\n") ; 

   /* This is slightly slower, but okay to use */ 
   printf("Method 2: ") ;
   length = strlen(str) ;
   for(i = 0; i < length; i++) 
   {
      c = str[i] ;
      c = toupper(c) ;
      printf("%c", c) ;
   }
   printf("\n\n") ; 

   /* This is the slowest - Don't use this method! */ 
   printf("Method 3: ") ;
   for(i = 0; i < strlen(str); i++) 
   {
      c = str[i] ;
      c = toupper(c) ;
      printf("%c", c) ;
   }
   printf("\n\n") ; 

   return 0;
}

The Sample Run