6.4. Initialising Arrays

In the above example we initialised the array hourly_wage by placing a comma separated list of values in curly braces. Using this method you can initialise as few or as many array elements as you like however you cannot initialise an element without initialising all the previous elements. If you initialise some but not all elements of an array the remaining elements will be automatically initialised to zero.

To get around this inconvenience, a GNU extension to the C language allows you to initialise array elements selectively by number. When initialised by number, the elements can be placed in any order withing the curly braces preceded by [index]=value. Like so:

Example 6-2. initialise_array.c

#include <stdio.h>

  int i;
  int first_array[100] = { [90]=4, [0]=5, [98]=6 };
  double second_array[5] = { [3] = 1.01, [4] = 1.02 };

  printf("sure enough, first_array[90] == %d\n\n", first_array[90]);
  printf("sure enough, first_array[99] == %d\n\n", first_array[99]);

  for (i = 0; i < 5; i++}
    printf("value of second_array[%d] is %f\n", i, second_array[i]);

  return 0;