Arrays as Function Arguments

Part of the Fundamentals section of Coddy's C journey — lesson 58 of 63.

Arrays can be passed as arguments to functions in C. When an array is passed to a function, what is actually passed is the memory address of the first element.

Declare an array and a function that takes it as an argument:

void displayArray(int arr[], int size) {
    for(int i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
}

Create an array and call the function:

int numbers[5] = {10, 20, 30, 40, 50};
displayArray(numbers, 5);

When you pass an array to a function, changes made to the array inside the function will affect the original array:

void doubleValues(int arr[], int size) {
    for(int i = 0; i < size; i++) {
        arr[i] = arr[i] * 2;
    }
}

// Call the function
doubleValues(numbers, 5);
// Now numbers contains: {20, 40, 60, 80, 100}

Challenge

Easy

Create a function named sumArray that takes two arguments:

An integer array (arr).
An integer (size) representing the size of the array.

The function should calculate and return the sum of all elements in the array.

Then, in the main function:

Read an integer n (the size of the array).
Read n integers and store them in an array.
Call the sumArray function with the array.
Print the sum in the format: "Sum: X" (where X is the sum).

Cheat sheet

Arrays are passed to functions by reference (memory address of first element):

void displayArray(int arr[], int size) {
    for(int i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
}

Call the function with array name and size:

int numbers[5] = {10, 20, 30, 40, 50};
displayArray(numbers, 5);

Changes made to array inside function affect the original array:

void doubleValues(int arr[], int size) {
    for(int i = 0; i < size; i++) {
        arr[i] = arr[i] * 2;
    }
}

Try it yourself

#include <stdio.h>

// Write your sumArray function here

int main() {
    int n;
    scanf("%d", &n);
    
    int arr[n];
    for(int i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }
    
    // Call the sumArray function and print the result
    
    return 0;
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Fundamentals

1Introduction

C Language Hello World!Comments Basic Program Structure

4Control Flow

If Statement If - Else Else-If Switch Case Ternary Conditional Operator Recap Challenge Nested If - Else

7Functions

Declare a Function Return Types Parameters Recap Challenge #1 Recursion Basics Function Prototypes Recap Challenge #2