What Is 1D Array in Data Structure?


Heather Bennett

In data structure, an array is a collection of elements that are stored in contiguous memory locations. It provides a way to store multiple values of the same data type under a single variable name. Arrays can be one-dimensional (1D) or multi-dimensional.

What Is a 1D Array?

A 1D array is a linear collection of elements arranged in a single row or column. Each element in the array is accessed by its index, which represents its position within the array.

A 1D array can be visualized as a row of boxes, where each box holds a value. The first box is assigned an index of 0, and subsequent boxes are assigned sequential indices.

Declaring and Initializing a 1D Array

To declare and initialize a 1D array in most programming languages, you need to specify the data type of the elements it will hold and the number of elements it can store.

For example, in C++, you can declare an integer array named numbers with 5 elements as follows:

int numbers[5];

You can also initialize the array with specific values at the time of declaration:

int numbers[] = {10, 20, 30, 40, 50};

This initializes numbers[0] to 10, numbers[1] to 20, and so on.

The Indexing Scheme

A key feature of arrays is their indexing scheme. In most programming languages, arrays are zero-indexed, meaning the first element has an index of 0.

For example, in our numbers array, numbers[0] refers to the first element with a value of 10.

Accessing and Modifying Array Elements

To access or modify elements in a 1D array, you need to use the array name followed by the index enclosed in square brackets ([]).

To access the third element in our numbers array, you would use numbers[2]. This would return the value 30.

You can also assign a new value to an element using the same syntax. For example, to change the second element value to 25, you would write: numbers[1] = 25;

The Length of a 1D Array

The length of a 1D array represents the number of elements it can store. It is often useful to know this information when iterating over an array or performing other operations.

In most programming languages, you can obtain the length of an array using the built-in length, size(), or similar functions.

An Example:

// C++ example
#include <iostream>

int main() {
    int numbers[] = {10, 20, 30, 40, 50};
    int length = sizeof(numbers) / sizeof(numbers[0]);

    std::cout << "The length of numbers is " << length << std::endl;

    return 0;

The output of the above code will be:

The length of numbers is 5

Advantages of 1D Arrays

  • Efficient memory usage: Arrays allow for efficient memory allocation as elements are stored in contiguous memory locations.
  • Random access: Elements in an array can be accessed randomly using their indices, making it easy to retrieve specific values.
  • Ease of iteration: Arrays can be easily traversed using loops, enabling efficient processing of multiple elements.


A 1D array is a fundamental data structure that provides a way to store and access multiple values under a single variable name. Understanding how to declare, initialize, and manipulate elements in a 1D array is crucial for building more complex programs.

By leveraging the power of arrays, you can efficiently store and process large amounts of data in various programming languages.

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