**The Program in C that uses a function that calculates factorial of a given number is given below**:

```
#include <stdio.h>
int factorial(int n) {
int result = 1;
for (int i = 1; i <= n; i++) {
result *= i;
}
return result;
}
int main() {
int n;
printf("Enter a positive integer: ");
scanf("%d", &n);
printf("The factorial of %d is: %d\n", n, factorial(n));
return 0;
}
```

## Output:

Enter a positive integer: 9

The factorial of 9 is: 362880

## Pro-Tips**💡**

In this program, the `factorial()`

function takes an integer as an argument and uses a for loop to calculate the factorial of that number by iterating from 1 to the given number and multiply each number with the result.

In the main function, the program prompts the user to enter a positive integer and then passes the entered number to the `factorial()`

function, which returns the factorial of the given number.

The program then prints the result on the screen.

The program uses a for loop to calculate the factorial, which is efficient for small numbers, for larger numbers the program may take more time and space.

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