Arrays of Pointers — String Lists and Pointer Tables

C in 100 Seconds, Episode 28

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An array of pointers holds addresses instead of values. Each element points somewhere else in memory. This is how C handles lists of strings, command-line arguments, and dispatch tables.

Array of String Pointers

The most common use — a list of strings:

char *colors[] = {"red", "green", "blue"};

Each element is a char* pointing to a string literal. The array itself holds three pointers, not three copies of the strings.

Iterating

The sizeof trick works the same way — total size divided by one element:

int len = sizeof(colors) / sizeof(colors[0]);
for (int i = 0; i < len; i++) {
  printf("colors[%d] = %s\n", i, colors[i]);
}

Array of Int Pointers

You can also store pointers to individual variables:

int a = 10, b = 20, c = 30;
int *nums[] = {&a, &b, &c};

Each element holds an address. Dereference with *nums[i] to get the value.

Why This Matters

• argv — command-line arguments are char *argv[]
• String tables — menus, error messages, configuration
• Dispatch tables — arrays of function pointers for routing
• Dynamic collections — arrays of malloc'd pointers

Full Code

#include <stdio.h>

int main() {
  char *colors[] = {"red", "green", "blue"};
  int len = sizeof(colors) / sizeof(colors[0]);

  for (int i = 0; i < len; i++) {
    printf("colors[%d] = %s\n", i, colors[i]);
  }

  int a = 10, b = 20, c = 30;
  int *nums[] = {&a, &b, &c};

  for (int i = 0; i < 3; i++) {
    printf("*nums[%d] = %d\n", i, *nums[i]);
  }

  return 0;
}

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Next episode: Double Pointers — pointer to pointer, dynamic 2D arrays.

Student code: github.com/GoCelesteAI/c-in-100-seconds/episode28