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

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

Vinay Khatri
Last updated on April 23, 2024

    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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