pass the pointer to the function

To pass a pointer to a function in the C programming language, you can declare a function parameter of type "pointer to a certain data type". Here's an example:

#include <stdio.h>

void changeValue(int *ptr) {
    *ptr = 10;
}

int main() {
    int num = 5;
    printf("Before function call: %d\n", num);
    changeValue(&num);
    printf("After function call: %d\n", num);
    return 0;
}

In this example, the changeValue function takes a pointer to an integer (int ptr) as a parameter. Inside the function, we dereference the pointer (ptr) to access the value at the memory location it points to and assign it a new value (10 in this case).

In the main function, we declare an integer variable num and initialize it with 5. We then call the changeValue function, passing the address of num (&num) as an argument. This allows the function to modify the value of num directly, even though it is defined in the main function.

The output of this code will be:

Before function call: 5
After function call: 10

By passing a pointer to a function, you can modify variables in the calling function, even though they are outside the function's scope.