What is a One-dimensional Array?

A one-dimensional array, also called a 1D array, is an array that stores elements in a single line or single row.

In simple words, a one-dimensional array is like a list of values arranged one after another. Each value has a position number called an index.

For example, if we want to store marks of five students, we can use one array:

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

Here, marks is a one-dimensional array because all values are stored in a single sequence.

Easy Real-Life Example

A one-dimensional array works in the same way. It stores values one after another, and each value can be found using its position.

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

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

Why is it Called One-dimensional?

It is called one-dimensional because data is stored in only one direction: as a single row or list.

A one-dimensional array does not have rows and columns like a table. It only has one line of elements.

One-dimensional Array:

[10, 20, 30, 40, 50]

It needs only one index to access an element.

numbers[2]

The above expression accesses the value stored at index 2.

Main Parts of a One-dimensional Array

General Syntax of One-dimensional Array

The exact syntax changes from language to language, but the general language-neutral format is:

arrayName = [value1, value2, value3, value4]

Example:

scores = [45, 78, 92, 66, 81]

Here, scores is a one-dimensional array containing five numbers.

Indexing in One-dimensional Array

Each element in a one-dimensional array has an index. The index is used to access, update, or process the value.

scores = [45, 78, 92, 66, 81]

Index 0 → 45
Index 1 → 78
Index 2 → 92
Index 3 → 66
Index 4 → 81

For example, if an array has 5 elements, the last index is 5 - 1 = 4.

Accessing Elements from a One-dimensional Array

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

scores = [45, 78, 92, 66, 81]

DISPLAY scores[0]
DISPLAY scores[2]
DISPLAY scores[4]

Expected Output

45
92
81

scores[0] gives the first element, scores[2] gives the third element, and scores[4] gives the fifth element.

Updating Elements in a One-dimensional Array

We can update an existing element by assigning a new value to a specific index.

scores = [45, 78, 92, 66, 81]

SET scores[1] = 80

DISPLAY scores

Updated Array

[45, 80, 92, 66, 81]

The value at index 1 changed from 78 to 80.

Traversing a One-dimensional Array

Traversal means visiting each element of the array one by one.

Loops are commonly used to traverse one-dimensional arrays.

scores = [45, 78, 92, 66, 81]

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

Expected Output

45
78
92
66
81

The loop starts at index 0 and continues until the last valid index.

Example 1: Store and Display Student Marks

/*
This program stores and displays student marks using a one-dimensional array.
*/

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

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

Expected Output

Student 1 Mark: 85
Student 2 Mark: 90
Student 3 Mark: 78
Student 4 Mark: 88
Student 5 Mark: 92

Example 2: Calculate Total of Array Elements

/*
This program calculates the total of all elements in a one-dimensional array.
*/

ENTRY POINT
    DECLARE numbers AS ARRAY = [10, 20, 30, 40, 50]
    DECLARE total AS INTEGER = 0

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

    DISPLAY "Total: " + total
END ENTRY POINT

Expected Output

Total: 150

Example 3: Find Average of Array Elements

/*
This program calculates average marks using a one-dimensional array.
*/

ENTRY POINT
    DECLARE marks AS ARRAY = [85, 90, 78, 88, 92]
    DECLARE total AS INTEGER = 0
    DECLARE average AS DECIMAL = 0.0

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

    SET average = total / length(marks)

    DISPLAY "Average Marks: " + average
END ENTRY POINT

Expected Output

Average Marks: 86.6

Example 4: Find Highest Value

/*
This program finds the highest value in a one-dimensional array.
*/

ENTRY POINT
    DECLARE scores AS ARRAY = [45, 78, 92, 66, 81]
    DECLARE highest AS INTEGER = scores[0]

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

    DISPLAY "Highest Score: " + highest
END ENTRY POINT

Expected Output

Highest Score: 92

Example 5: Search an Element

/*
This program searches for a value in a one-dimensional array.
*/

ENTRY POINT
    DECLARE numbers AS ARRAY = [10, 20, 30, 40, 50]
    DECLARE target AS INTEGER = 30
    DECLARE isFound AS BOOLEAN = false

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

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

Expected Output

30 found in the array

Common Operations on One-dimensional Arrays

One-dimensional Array vs Two-dimensional Array

Advantages of One-dimensional Arrays

Limitations of One-dimensional Arrays

Common Beginner Mistakes

Best Practices for One-dimensional Arrays

Prerequisites Before Learning One-dimensional Array

Students should already understand:

Practice Activity: Identify Index and Value

Study the following one-dimensional array:

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

Questions

1. What is the value at index 0?
2. What is the value at index 2?
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 2 = 30
3. Length = 5
4. Last index = 4
5. Value at last index = 50

Mini Quiz

Interview Questions on One-dimensional Array

Quick Summary