Array of pointers

An array of pointers is an array whose elements are all pointers, each holding the address of a variable or a string.

Declaration: data_type *name[size]; for example int *p[3]; is an array of 3 pointers to integers.

int x = 10, y = 20, z = 30;
int *p[3] = {&x, &y, &z};     /* p[i] stores the address of x, y, z */
printf("%d", *p[1]);          /* prints 20 */

The commonest use is an array of strings, where each pointer points to a string, and strings of different lengths need no wasted space:

char *day[3] = {"Sunday", "Monday", "Tuesday"};

Sorting these strings only needs the pointers to be swapped, not the characters. It is also used for arrays of structure pointers and argv (command line arguments).

#include <stdio.h>

int main(void)
{
    char *day[3] = {"Sunday", "Monday", "Tuesday"};   /* array of 3 pointers */
    int x = 10, y = 20, z = 30;
    int *p[3] = {&x, &y, &z};

    for (int i = 0; i < 3; i++)
        printf("%s  %d\n", day[i], *p[i]);
    return 0;
}

Output:

Sunday  10
Monday  20
Tuesday  30