C :

#include <stdio.h>
#include <string.h>
int main() {
        char encode[101], decode[101];
        int i, length;
        gets(encode);
        length = strlen(encode);
        decode[length] = '\0';
        for (i = 0;i < length;i++) {
                if ('A' <= encode[i] && encode[i] <= 'Z') {
                        decode[i] = 'A' + ('Z' - encode[i]);
                } else if ('a' <= encode[i] && encode[i] <= 'z') {
                        decode[i] = 'a' + ('z' - encode[i]);
                } else {
                        decode[i] = encode[i];
                }
        }
        puts(decode);
        return 0;
}

C++ :

#include <stdio.h>
#include <string.h>
int main() {
	char encode[101], decode[101];
	int i, length;
	gets(encode);
	length = strlen(encode);
	decode[length] = '\0';
	for (i = 0;i < length;i++) {
		if ('A' <= encode[i] && encode[i] <= 'Z') {
			decode[i] = 'A' + ('Z' - encode[i]);
		} else if ('a' <= encode[i] && encode[i] <= 'z') {
			decode[i] = 'a' + ('z' - encode[i]);
		} else {
			decode[i] = encode[i];
		}
	}
	puts(decode);
	return 0;
}

Pascal :

var 
  i:longint;
  s,sa:string;
  
function turn(c:char):char;
var ch:char;
begin
  ch:=upcase(c);
  if( not(ch in ['A'..'Z']) ) then exit(c);
  ch:=chr( ord('A')+ord('Z')-ord(ch) );
  if(upcase(c)=c) then exit(ch)
    else exit(lowercase(ch));
end;
  
begin
  readln(s); sa:='';
  for i:=1 to length(s) do
    sa:=sa+turn(s[i]);
  writeln(sa);
end.

Java :

import java.util.Scanner;

public class Main {
   private static Scanner s = new Scanner(System.in) ;
   public static void main(String[] args) {
	   String str = s.nextLine() ;
	   
	   System.out.println(f(str));
   }
   
   public static String f(String str){
	   char c[] = str.toCharArray() ;
	   
	   for (int i = 0; i < c.length; i++) {
		  if(c[i]>='a'&&c[i]<='z')
		  c[i] = (char) ('a'+24-(c[i]-'a')+1) ;
		  else  if(c[i]>='A'&&c[i]<='Z'){
			  c[i] = (char) ('A'+24-(c[i]-'A')+1) ;
		  }
	   }
	   
	   return new String(c) ;
   }
}