C Arrays


Arrays are used to store multiple values in a single variable, instead of declaring separate variables for each value.

To create an array, define the data type (like int) and specify the name of the array followed by square brackets [].

To insert values to it, use a comma-separated list, inside curly braces:

int myNumbers[] = {25, 50, 75, 100};

We have now created a variable that holds an array of four integers.

Access the Elements of an Array

To access an array element, refer to its index number.

Array indexes start with 0: [0] is the first element. [1] is the second element, etc.

This statement accesses the value of the first element [0] in myNumbers:


int myNumbers[] = {25, 50, 75, 100};
printf("%d", myNumbers[0]);

// Outputs 25

Change an Array Element

To change the value of a specific element, refer to the index number:


myNumbers[0] = 33;


int myNumbers[] = {25, 50, 75, 100};
myNumbers[0] = 33;

printf("%d", myNumbers[0]);

// Now outputs 33 instead of 25

Loop Through an Array

You can loop through the array elements with the for loop.

The following example outputs all elements in the myNumbers array:


int myNumbers[] = {25, 50, 75, 100};
int i;

for (i = 0; i < 4; i++) {
  printf("%dn", myNumbers[i]);

Set Array Size

Another common way to create arrays, is to specify the size of the array, and add elements later:


// Declare an array of four integers:
int myNumbers[4];

// Add elements
myNumbers[0] = 25;
myNumbers[1] = 50;
myNumbers[2] = 75;
myNumbers[3] = 100;

Using this method, you should know the size of the array, in order for the program to store enough memory.

You are not able to change the size of the array after creation.

C Exercises

Test Yourself With Exercises


Create an array of type int called myNumbers.

   {25, 50, 75, 100};