Recursion Using - C
  
 Source Code
  

  
#include<stdio.h>

int GCD(int a, int b);

void main() {
    int a, b;
    printf("Enter two Positive Integers: ");
    scanf("%d %d", &a, &b);
    printf("G.C.D of %d and %d is %d.", a, b, GCD(a, b));
}

int GCD(int a, int b) {
    if (b != 0)
        return GCD(b, a % b);
    else
        return a;
}

Enter two Positive Integers:  40   60
G.C.D of 40 and 60 is 20.

  
Iteration Using - C
  
 Source Code
  

  
#include<stdio.h>

int GCD(int a, int b);
  
void main() {
    int a, b;
  
    printf("Enter two Positive Integers: ");
    scanf("%d %d", &a, &b);
  
    printf("G.C.D of %d and %d is %d.", a, b, GCD(a,b));
}
  
int GCD(int a, int b) {
  int  i, gcd;
      for(i=1; i <= a && i <= b; ++i) {
          if(a%i==0 && b%i==0)
          gcd = i;
      }
      return gcd;
  } 
  

Enter two Positive Integers:  144   24
G.C.D of 144 and 24 is 24.

        
Rescursion Using - C++
        
 Source Code
        

        
#include<iostream>
using namespace std;

int GCD(int a, int b);

int main() {
    int a, b;
    cout<< "Enter two Positive Integers: ";
    cin>> a>> b;
    cout<< "G.C.D of "<< a<< " and "<< b<< " is "<< GCD(a,b);
    return 0;
}

int GCD(int a, int b) {
    if (b != 0)
        return GCD(b, a % b);
    else
        return a;
}
   

Enter two Positive Integers:  30  6
G.C.D of 30 and 6 is 6

  
Iteration Using - C++
  
 Source Code
  

  
#include<iostream>
using namespace std;

int GCD(int a, int b);

int main() {
    int a, b;
    cout<< "Enter two Positive Integers: ";
    cin>> a>> b;
    cout<< "G.C.D of "<< a<< " and "<< b<< " is "<< GCD(a,b);
    return 0;
}

int GCD(int a, int b) {
	int  i, gcd;
    
	for(i=1; i <= a && i <= b; ++i) {
        if(a%i==0 && b%i==0) 		
        gcd = i;
    }
    return gcd;
}

Enter two Positive Integers: 150   50
G.C.D of 150 and 50 is 50