Code - Pointers Demo

// Some examples of using pointers
// Marc Chee (cs1511@cse.unsw.edu.au), March 2021

#include <stdio.h>

void increment_int(int n);
void increment_ptr(int *n);

int main(void) {
    int i = 100;
    // create a pointer called ip that points at i
    // it stores the address of i
    int *ip = &i;
    printf("%p is the address of i, which has the value %d\n", ip, *ip);
    
    increment_int(i);
    printf("i, %d, hasn't changed.\n", i);
    increment_ptr(ip);
    printf("i, %d, has now changed.\n", i);
    
    int numbers[10];
    
    // showing that arrays are actually pointers
    // to chunks of memory
    printf("%p\n", &numbers[0]);
    printf("%p\n", numbers);

}

// This function will have no effect!
// It only modifies it's own variable, n, not the variable in the main
void increment_int(int n) { 
    n = n + 1; 
}
// This function will affect whatever n is pointing at
void increment_ptr(int *n) { 
    *n = *n + 1; 
}