C :

#include<stdio.h>
#include<string.h>
int main()
{
	char a[102];
	int i,l;
	gets(a);
	l=strlen(a);
	for(i=l-1;i>=0;i--)
		printf("%c",a[i]);
	printf("\n");
}

C++ :

#include <stdio.h>
#include <string.h>
int main() {
	void reverse(char array[], int n);
	int i;
	char str[101];
	gets(str);
	reverse(str, strlen(str));
	for (i = 0;str[i] != '\0';i++) {
		printf("%c", str[i]);
	}
	puts("");
	return 0;
}
void reverse(char array[], int n) {
	int i;
	char temp;
	for (i = 0;i + i < n;i++) {
		temp = array[i];
		array[i] = array[n - 1 - i];
		array[n - 1 - i] = temp;
	}
}

Pascal :

var
  n:string;
  i:longint;
begin
  readln(n);
  for i:=length(n) downto 1 do write(n[i]);
  writeln;
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() ;
	  
	  char[]c = str.toCharArray() ;
	  
	  for (int i = c.length-1; i >= 0 ; i--) {
		 System.out.print(c[i]);
	   }
	  
	  System.out.println();
   }
}