The main benefit of arrays is the ability to work with large amounts of data without assigning each piece of data its own variable name; therefore arrays usually contain many elements. To work with these elements, you will probably have to do something repeatedly. As you learned earlier in the course, a loop is used in order to execute repeated code. The technique of using a loop on an array is called “looping through the array.” Recall the two kinds of loops: a for loop and a while loop.

Let’s first take a look at how to loop through an array using a while loop. Consider the example of having an array consisting of 20 random integers and you wish to print its contents to the screen. Here’s how this is done with a while loop:

#include<stdio.h>

int main() {
  int arr[] = {6, 9, 18, 37, 4, 23, 27, 16, 1, 30, 22, 7, 10, 25, 3, 2, 35, 11, 19, 28}; // Array
  int i = 0; // Initialize index i to zero
  while(i < 20){ // while loop
    printf("%i\n", arr[i]); // Access element at index i in arr and print 
    i++; // Increment the index
  }
}

In this piece of code, we have the 20 integer array arr. An index variable is declared and initialized outside of the loop. The loop runs for indices less than the size of the array (in this case, it is 20). The element at index i is printed along with a new line. Finally, the index is incremented by one.

This same process can be done using a for loop like so:

#include<stdio.h>

int main() {
  int arr[] = {6, 9, 18, 37, 4, 23, 27, 16, 1, 30, 22, 7, 10, 25, 3, 2, 35, 11, 19, 28}; // Array
  for(int i = 0; i < 20; i++){ // for loop
    printf("%i\n", arr[i]); // Access element at index i in arr and print
  }
}