C Arrays
Arrays let you store many values of the same type in a single variable, instead of declaring a separate variable for each value. If you needed to keep track of 100 test scores, declaring score1, score2, all the way to score100 would be painful. An array solves this by grouping the values together and giving you a simple number, called an index, to reach each one.
Creating an Array
To declare an array in C, you write the data type, the array name, and then the number of elements inside square brackets. The number in the brackets is the size of the array, which is how many values it can hold. You can also fill the array with values right away using curly braces.
Declaring and initializing an array
#include <stdio.h>
int main() {
int myNumbers[4] = {25, 50, 75, 100};
printf("First value: %d\n", myNumbers[0]);
printf("Second value: %d\n", myNumbers[1]);
return 0;
}Changing and Accessing Elements
You can read any element by using its index, and you can change an element by assigning a new value to that index. This makes arrays flexible: you set up the storage once, then update individual slots whenever you need to.
Changing an element by index
#include <stdio.h>
int main() {
int myNumbers[4] = {25, 50, 75, 100};
myNumbers[0] = 33;
printf("New first value: %d\n", myNumbers[0]);
return 0;
}Looping Through an Array
Arrays and loops work well together. Because each element has a numbered index, you can use a for loop with a counter to visit every element one by one without repeating code.
Printing every element with a loop
#include <stdio.h>
int main() {
int myNumbers[4] = {25, 50, 75, 100};
for (int i = 0; i < 4; i++) {
printf("Index %d holds %d\n", i, myNumbers[i]);
}
return 0;
}Common array declarations
Exercise: C Arrays
How are indices numbered for a C array such as int arr[5]?
