ptr_ops.c

// ptr_ops.c -- pointer operations
#include <stdio.h>
int main(void)
{
    int urn[5] = {100, 200, 300, 400, 500};
    int *ptr1, *ptr2, *ptr3;

    ptr1 = urn;  // assign an address to a pointer
    ptr2 = &urn[2];  // ditto
    // dereference a pointer and take the address of a pointer
    printf("pointer value, dereferenced pointer, pointer address:\n");
    printf("ptr1 = %p, *ptr1 = %d, &ptr1 = %p\n", ptr1, *ptr1, &ptr1);

    // pointer addition
    ptr3 = ptr1 + 4;
    printf("\nadding an int to a pointer:\n");
    printf("ptr1 + 4 = %p, *(ptr4 + 3) = %d\n", ptr1 + 4, *(ptr1 + 3));
    ptr1++;  // increment a pointer
    printf("ptr1 = %p, *ptr1 = %d, &ptr1 = %p\n", ptr1, *ptr1, &ptr1);
    ptr2--;  // decrement a pointer
    printf("\nvalues after ptr1++:\n");
    printf("ptr2 = %p, *ptr2 = %d, &ptr2 = %p\n", ptr2, *ptr2, &ptr2);
    --ptr1;  // restore to original value
    ++ptr2;  // restore to original value
    printf("\nPointers reset to original values:\n");
    printf("ptr1 = %p, *ptr1 = %p, ptr2 - ptr1 = %td\n", ptr2, ptr1, ptr2 - ptr1);  // subtract an integer from a pointer
    printf("\nsubtracting an int from a pointer:\n");
    printf("ptr3 = %p, ptr3 - 2 = %p\n", ptr3, ptr3 - 2);

    return 0;
}