Program to Calculate the Factorial of an Integer [C, C++, Python & Java]

In this blog post, we will write a program in C, C++, Python, and Java to calculate the factorial of a user-entered integer.

To write a program, the following are the prerequisites:

• Data types
• Programming operators
• if...else statement
• for loop

What is a Factorial?

Factorial is a mathematical concept that uses the ! symbol and is used in permutation, combination, and probability. A factorial of a number, n, is the product of that number with every whole number less than or equal to n.

For example, a factorial of 3 (3!) = 3*2*1 = 6.

Here is another example, 5! = 5*4*3*2*1 = 120.

Note - The factorial of 0 (0!) is equal to 1, and the factorial of a negative number does not exist.

Uses or Applications of a Factorial

• Recursion
• Permutation
• Combination
• Probability distribution

C Program to Find the Factorial of an Integer

#include<stdio.h>
#include<conio.h>
void main()
{
long num, i,fact=1;
clrscr();
printf("Enter a number:");
scanf("%ld",&num);
for(i=num; i>=1; i--)
  { fact*=i;
  }
printf("The factorial of the number %ld is %ld",num,fact);
 getch();
}

Output:

Enter a number:10
The factorial of the number 10 is 3628800

C++ Program to Find the Factorial of an Integer

#include<iostream.h>
#include<conio.h>
#include<stdio.h>
#include<math.h>
void main()
{
clrscr();
int num,fact=1;
cout<<"Enter a number: ";
cin>>num;
for(int i=1; i<=num; i++)
fact *= i;
if(num==0)
cout<<"The factorial is 1";
else
cout<<"The factorial of "<<num<<" is "<<fact;
getch();
}

Output:

Enter a Number: 5
The factorial of 5 is 120

Python Program to Find the Factorial of an Integer

num =int(input("Enter a Number: "))
fact=1
for i in range(1,num+1):
    fact*=i
if num==0:
    print("The factorial is 1")
else:
    print("The factorial of",num,"is",fact)

Output:

Enter a Number: 6
The factorial of 6 is 720

Java Program to Find the Factorial of an Integer

import java.util.*;
public class Main
{
	public static void main(String[] args) {
	    int i, fact=1;
	    Scanner s = new Scanner(System.in);
		System.out.println("Enter a number: ");
		int num = s.nextInt();
        if (num == 0)
        {
            System.out.println("The factorial is 1");
        }
        else
        {
            for(i=1; i<=num; ++i)
		{
		    fact=fact*i;
		}
	    System.out.println("The factorial of " +num+ " is " +fact);
        }
	}
}

Output:

Enter a number: 5
The factorial of 5 is 120

Conclusion

Wasn't it easy to write a program to calculate the factorial of any number? This is a very basic program. You can add a condition for negative numbers, i.e., if a user enters a negative number, it must display the message "The factorial of a negative number does not exist".

We hope this article has helped you write a program to calculate the factorial of an integer. If you have any doubts, do let us know in the comments.

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