What is an Array?

An array is a data structure used to store multiple values under a single variable name.

In simple words, an array is like a container that can hold many related values together. Instead of creating separate variables for each value, we can store all values in one array.

For example, if we want to store marks of five students, we do not need five separate variables. We can store all marks inside one array.

marks = [85, 90, 78, 88, 92]

Here, marks is an array that stores five values.

Easy Real-Life Example

An array works in a similar way. It has multiple positions, and each position stores one value.

Index:   0    1    2    3    4
Value:  85   90   78   88   92

In most programming languages, array indexing starts from 0. That means the first element is at index 0, not index 1.

Why are Arrays Needed?

Arrays are needed because storing many related values using separate variables becomes difficult and messy.

Without Array

studentMark1 = 85
studentMark2 = 90
studentMark3 = 78
studentMark4 = 88
studentMark5 = 92

This approach may work for five values, but it becomes difficult when there are hundreds or thousands of values.

With Array

studentMarks = [85, 90, 78, 88, 92]

This is cleaner, easier to manage, and easier to process using loops.

Main Parts of an Array

General Syntax of an Array

The exact syntax of arrays differs from language to language, but the general idea is:

arrayName = [value1, value2, value3, value4]

Example:

studentNames = ["Aman", "Riya", "Sohan", "Meera"]

Here, studentNames is an array that stores four text values.

What is an Array Index?

An index is the position number of an element inside an array.

Most programming languages start array indexing from 0. So the first element is stored at index 0, the second element at index 1, and so on.

fruits = ["Apple", "Banana", "Mango", "Orange"]

Index 0 → Apple
Index 1 → Banana
Index 2 → Mango
Index 3 → Orange

If an array has 4 elements, the indexes are 0, 1, 2, and 3.

Accessing Array Elements

To access an element, we use the array name and the index of the element.

fruits = ["Apple", "Banana", "Mango", "Orange"]

DISPLAY fruits[0]
DISPLAY fruits[2]

Expected Output

Apple
Mango

fruits[0] gives the first element, and fruits[2] gives the third element.

Updating Array Elements

We can change an existing value in an array by using its index.

marks = [85, 90, 78, 88, 92]

SET marks[2] = 80

DISPLAY marks

Updated Array

[85, 90, 80, 88, 92]

The value at index 2 changed from 78 to 80.

Traversing an Array

Traversing means visiting each element of an array one by one.

Loops are commonly used to traverse arrays.

marks = [85, 90, 78, 88, 92]

FOR index FROM 0 TO length(marks) - 1
    DISPLAY marks[index]
END FOR

Expected Output

85
90
78
88
92

This loop starts from index 0 and visits every value in the array.

Example 1: Store Student Marks

/*
This program stores and displays student marks using an array.
*/

ENTRY POINT
    DECLARE marks AS ARRAY = [85, 90, 78, 88, 92]

    FOR index FROM 0 TO length(marks) - 1
        DISPLAY "Mark: " + marks[index]
    END FOR
END ENTRY POINT

Example 2: Find Total Marks

/*
This program calculates total marks from an array.
*/

ENTRY POINT
    DECLARE marks AS ARRAY = [85, 90, 78, 88, 92]
    DECLARE total AS INTEGER = 0

    FOR index FROM 0 TO length(marks) - 1
        SET total = total + marks[index]
    END FOR

    DISPLAY "Total Marks: " + total
END ENTRY POINT

Expected Output

Total Marks: 433

Example 3: Find Highest Marks

/*
This program finds the highest mark in an array.
*/

ENTRY POINT
    DECLARE marks AS ARRAY = [85, 90, 78, 88, 92]
    DECLARE highest AS INTEGER = marks[0]

    FOR index FROM 1 TO length(marks) - 1
        IF marks[index] > highest THEN
            SET highest = marks[index]
        END IF
    END FOR

    DISPLAY "Highest Mark: " + highest
END ENTRY POINT

Expected Output

Highest Mark: 92

Example 4: Search an Element in an Array

/*
This program searches for a name inside an array.
*/

ENTRY POINT
    DECLARE names AS ARRAY = ["Aman", "Riya", "Sohan", "Meera"]
    DECLARE targetName AS TEXT = "Sohan"
    DECLARE isFound AS BOOLEAN = false

    FOR index FROM 0 TO length(names) - 1
        IF names[index] == targetName THEN
            SET isFound = true
            BREAK
        END IF
    END FOR

    IF isFound == true THEN
        DISPLAY targetName + " found in the array"
    ELSE
        DISPLAY targetName + " not found in the array"
    END IF
END ENTRY POINT

Common Array Operations

Types of Arrays

Arrays can be classified in different ways.

1. One-Dimensional Array

A one-dimensional array stores values in a single line or list.

marks = [85, 90, 78, 88, 92]

2. Two-Dimensional Array

A two-dimensional array stores data in rows and columns, like a table.

matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

A two-dimensional array is useful for tables, grids, matrices, game boards, and seat arrangements.

3. Multi-Dimensional Array

A multi-dimensional array has more than two dimensions. It is used when data has multiple levels.

Array vs Normal Variables

Array vs List

In some programming languages, arrays and lists are different. In some languages, list-like structures are commonly used instead of traditional arrays.

Advantages of Arrays

Limitations of Arrays

Common Beginner Mistakes

Best Practices for Arrays

Prerequisites Before Learning Arrays

To understand arrays properly, students should already know:

Practice Activity: Identify Array Elements

Study the array below and answer the questions.

numbers = [10, 20, 30, 40, 50]

Questions

1. What is the value at index 0?
2. What is the value at index 3?
3. What is the length of the array?
4. What is the last index?
5. What is the value at the last index?

Sample Answers

1. Value at index 0 = 10
2. Value at index 3 = 40
3. Length = 5
4. Last index = 4
5. Value at last index = 50

Mini Quiz

Interview Questions on Arrays

Quick Summary