 Hello friends, I am Sanjay Gupta. I welcome you on my YouTube channel. You can watch various programming related videos on my channel. It contains more than 800 videos. You can search these videos through the keyword programming by Sanjay Gupta. In this video, I am going to demonstrate you how you can reuse or call a function more than one time in C programming. For example, I am taking factorial program. First of all, I am going to include a header file as tdf.h. Then I am declaring a function whose name is fact, its return type is int and its argument type is int. And it will be receiving only one argument as input. After that, I am defining main function. I have declared some variables. Now I am going to print a message, enter a number. To read that number, I am using scanf and the entered number will be stored inside n1. Now I am going to call fact function and passing n1 variable into it. This is calling a function and the returned result will be available in f1 variable. So I am going to print it with the help of printf. So this way I have called fact function once right now. So before calling it more than one time, let me define its definition first. So this block will be known as definition. So whenever you want to reuse any function, you have to define it once but you can call it more than one time. So here I am going to implement the logic for factorial calculation. So this is the definition of fact function which is calculating factorial of n and the value will be returned with the help of variable f. So if we talk about line number 10, settling by n1 is passed as an argument which will be received through n which is available at line number 13. And the returned value of f from line number 18 will be received through f1 which is available at line number 10. So this way right now I have defined function once and I have called it only once. So let me execute this piece of code first. I am entering for n input and you can see the factorial is 34 which is correct. Now I am going to call this function definition second time in the same code. So printing this message enter second number that second number will be stored inside n2 variable. Now I am going to again call fact function and this time I am passing n2 and the returned value is available in f2. So I am going to display it with the help of printf. So now you can see I have called fact function twice. First time at line number 10 and second time at line number 14. But definition of function is provided only once. So this is the reusability of function whenever you want to execute a particular logic more than one time. So you have to define it once and you can call it more than one time in any of the other function. So here I am calling fact function into main but you can call this function into other functions also. So this way I have implemented the complete code in front of you. Now I am going to execute this code and this time two times numbers will be asked and two different factorials will be displayed on output screen. So you can see the output screen. First I entered four. So factorial displayed that is 24. Second number I entered as five and factorial is 120. So this way the program is working properly and I hope you have understood how we can reuse a function definition by calling it again and again at different line of statements. So this way I have demonstrated this code in front of you. I hope you have understood whatever I have explained. If you want to watch more programming related videos you can follow my YouTube channel. Thank you for watching this video.