### C Program to Find the GCD and LCM of Two Integers

This C Program calculates the GCD and LCM of two integers. Here GCD means Greatest Common Divisor. For two integers a and b, if there are any numbers d so that a / d and b / d doesn’t have any remainder, such a number is called a common divisor. Common divisors exist for any pair of integers a and b, since we know that 1 always divides any integer. We also know that common divisors can’t get too big since divisors can’t be any larger than the number they are dividing. Hence a common divisor d of a and b must have d <= a and d <= b. Here, LCM means Least Common Multiplies. For two integer a & b, to know if there are any smallest numbers d so that d / a and d / b doesn't have a remainder. such a number is called a Least Common Multiplier. Here is source code of the C program to calculate the GCD and LCM of two integers. The C program is successfully compiled and run on a Linux system. The program output is also shown below.
1.  /*
2.   * C program to find the GCD and LCM of two integers using Euclids' algorithm
3.   */
4.  #include <stdio.h>
5.
6.  void main()
7.  {
8.      int num1, num2, gcd, lcm, remainder, numerator, denominator;
9.
10.    printf("Enter two numbers\n");
11.    scanf("%d %d", &num1, &num2);
12.    if (num1 > num2)
13.    {
14.        numerator = num1;
15.        denominator = num2;
16.    }
17.    else
18.    {
19.        numerator = num2;
20.        denominator = num1;
21.    }
22.    remainder = num1 % num2;
23.    while (remainder != 0)
24.    {
25.        numerator   = denominator;
26.        denominator = remainder;
27.        remainder   = numerator % denominator;
28.    }
29.    gcd = denominator;
30.    lcm = num1 * num2 / gcd;
31.    printf("GCD of %d and %d = %d\n", num1, num2, gcd);
32.    printf("LCM of %d and %d = %d\n", num1, num2, lcm);
33.}

Output:

Enter two numbers
30
40
GCD of 30 and 40 = 30
LCM of 30 and 40

### Find factorial of a given number using the recursive function method in C

Write a program to find factorial of a given number using the recursive function method in C

Hints:

# Factorial !

Example: 4! is shorthand for 4 x 3 x 2 x 1
 The factorial function (symbol: !) means to multiply a series of descending natural numbers. Examples: 4! = 4 × 3 × 2 × 1 = 24 7! = 7 × 6 × 5 × 4 × 3 × 2 × 1 = 5040 1! = 1

Source Code:

#include<stdio.h>
//function declaration before the main
int factorial(int n);
//main function of the program
int main()
{
int n;
scanf("%d",&n);
//call function and print the final value at a time
printf("%d", factorial(n));
return 0;
}
int factorial(int n)
{
if(n!=1)
return n*factorial(n-1);
}

### Write a c program to sum of all elements from a two dimensional (2D) array

Figure of a Two Dimensional Array:

Program: