Detailed Explanation

1. Include the Standard I/O Library:
   • #include <stdio.h> is used to include the Standard Input/Output library. This allows the program to use functions like printf and scanf for displaying output and reading input.
2. Define the Factorial Function:
   • int factorial(int n) is a function that calculates the factorial of a number n.
   • The factorial of a number n is the product of all positive integers up to n. For example, the factorial of 5 (denoted as 5!) is 5 * 4 * 3 * 2 * 1 = 120.
   • The function uses recursion, which means it calls itself with a smaller value each time.
   • The base case is when n is 0. The factorial of 0 is defined as 1.
   • If n is greater than 0, the function returns n multiplied by the factorial of n - 1.
3. Main Function:
   • The main function is the entry point of the program.
   • int number; declares a variable to store the user’s input.
   • printf("Enter a number: "); prompts the user to enter a number.
   • scanf("%d", &number); reads the number input by the user and stores it in the number variable.
   • int result = factorial(number); calculates the factorial of the entered number by calling the factorial function.
   • printf("Factorial of %d is %d\n", number, result); prints the result to the screen.
   • return 0; indicates that the program has executed successfully.

How to Use This Code

1. Copy the Code:
   • Copy the C program code provided above.
2. Create a C File:
   • Open a text editor and paste the code into a new file. Save the file with a .c extension, such as factorial.c.
3. Compile the Code:
   • Use a C compiler to compile the code. If you’re using GCC, you can compile the program with:

     bash

     Copy code

     gcc factorial.c -o factorial

   • This command creates an executable file named factorial.
4. Run the Program:
   • Execute the compiled program from the command line:

     bash

     Copy code

     ./factorial

   • The program will prompt you to enter a number. Type a number and press Enter.
5. View the Result:
   • The program will calculate and display the factorial of the number you entered.

Example Output

If you enter the number 5, the output will be: