What is function in c

 

#include <stdio.h>

void ad(int num1, int num2);

int main()

{

    add(44,55);

    return 0;

}

void add ( int num1, int num2){

 int result= num1 +num2;

 printf("result of %d +%d = %d", num1,num2 ,result);

}

//********************************

Array to function 👇

#include <stdio.h>

void displaysinglemarks (int);

int main()

{int marks [] = {97,98,83,95,90};

   displaysinglemarks (marks [4]);

    return 0;

}

void displaysinglemarks (int marks) {

 printf ("-------------display single marks----------------\n"); 

 printf("%d", marks);

}

//*************************