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Writing to Arrays

Learn how to store values in an array after it has been declared as well as at the time of declaration.

We'll cover the following...

Assigning values to array cells

A memory location indexed by an array (for example grades[3]) is called a cell of that array. Just like we index an array to retrieve the value stored in it, we can also write to the same cell.

We can assign the integers 1 through 5 to the cells in our grades array like this:

C
#include <stdio.h>
int main(void)
{
  int grades[5];
  int i;
  for (i = 0; i < 5; i++) {
    grades[i] = i+1;
    printf("grades[%d] = %d\n", i, grades[i]);
  }
  return 0;
}

What can be dangerous however, is that we can also ask C to assign values to memory locations beyond the bounds of an array and C won’t complain:

C
#include <stdio.h>
int main(void)
{
  int grades[5];
  grades[5] = 999;
  grades[500] = 12345;
  printf("grades[500] = %d\n", grades[5]);
  printf("grades[500] = %d\n", grades[500]);
  return 0;
}

The reason this is ...