How the computer handles variables

parameters_is_address.c

#include <stdio.h>

void add(int *a) {
  *a = (*a) + 10;
}

int main(void) {
  int a = 7;
  add(&a);
  
  // print: a = 17
  printf("%d\n", a);
  system("pause");
  return 0;
}