Array Initialization | Arrays

Introduction

In the C programming language, arrays are a collection of elements of the same type stored in contiguous memory locations. Array initialization refers to the process of assigning values to an array when it is declared. This tutorial will guide you through various methods of initializing arrays in C.

Declaring and Initializing Arrays

To declare an array in C, you specify the type of its elements and the number of elements required by an array. Here is the syntax:

data_type array_name[array_size];

For example, to declare an array of 5 integers:

int numbers[5];

When you declare an array, its elements contain garbage values. To initialize an array, you can assign values to it at the time of declaration:

int numbers[5] = {1, 2, 3, 4, 5};

Partial Array Initialization

If you provide fewer values than the size of the array, the remaining elements are initialized to zero. For example:

int numbers[5] = {1, 2};

In this case, the array numbers will be initialized as follows:

numbers[0] = 1

numbers[1] = 2

numbers[2] = 0

numbers[3] = 0

numbers[4] = 0

Implicit Size Array Initialization

You can also let the compiler determine the size of the array by omitting the size and initializing it at the same time:

int numbers[] = {1, 2, 3, 4, 5};

In this case, the compiler will create an array of size 5.

Initializing Arrays at Runtime

Sometimes, you may want to initialize an array at runtime. You can use loops to assign values to an array dynamically. Here is an example:

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

The output of this program will be:

1 2 3 4 5

Multidimensional Array Initialization

Arrays in C can have multiple dimensions. For example, a two-dimensional array is an array of arrays. Here's how you can initialize a 2D array:

int matrix[2][3] = {{1, 2, 3}, {4, 5, 6}};

You can also initialize a 2D array partially:

int matrix[2][3] = {{1, 2}, {4}};

In this case, the missing elements will be initialized to zero:

matrix[0][0] = 1

matrix[0][1] = 2

matrix[0][2] = 0

matrix[1][0] = 4

matrix[1][1] = 0

matrix[1][2] = 0

Conclusion

Array initialization is a fundamental concept in C programming that allows you to assign values to an array at the time of declaration. This tutorial covered various methods of initializing arrays including full, partial, implicit size, runtime initialization, and multidimensional arrays. Understanding these methods will help you effectively manage and manipulate arrays in your C programs.

Array Initialization in C