C++ Program To Find The Area And Perimeter Of A Rectangle

In this article, you will learn how to write a C++ program that calculates the area and perimeter of a rectangle. This fundamental program helps illustrate basic input, computation, and output operations in C++.

Problem Statement

A rectangle is a four-sided shape where all angles are right angles (90 degrees) and opposite sides are equal in length. To find the area and perimeter of a rectangle, we use simple mathematical formulas based on its length and width. Automating these calculations with a C++ program can save time and reduce errors for various applications.

The formulas are:

• Area = Length × Width
• Perimeter = 2 × (Length + Width)

Example

If a rectangle has a length of 7.5 units and a width of 3.0 units, the program should produce an output similar to this:

Enter the length of the rectangle: 7.5
Enter the width of the rectangle: 3.0
Area of the rectangle: 22.5
Perimeter of the rectangle: 21

Background & Knowledge Prerequisites

To understand the C++ program, readers should be familiar with the following basic C++ concepts:

• Basic C++ syntax: How to write simple C++ statements.
• Variables: Declaring and using variables to store data (e.g., double for decimal numbers).
• Input/Output operations: Using std::cin to read user input and std::cout to display output.
• Arithmetic operators: Performing basic mathematical operations like addition (+), multiplication (*).

Use Cases or Case Studies

Calculating the area and perimeter of a rectangle is a fundamental operation with many practical applications:

• Construction and Architecture: Estimating materials needed for flooring, roofing, or painting a rectangular room.
• Gardening and Landscaping: Determining the amount of fence required for a rectangular garden or the area of turf needed.
• Game Development: Calculating bounding boxes for collision detection or rendering rectangular game objects.
• Graphic Design: Sizing and positioning elements in a layout, or calculating the printable area on a page.
• Robotics: Planning paths or operations within a rectangular workspace or determining the reach of a robotic arm in a rectangular area.

Solution Approaches

This problem can be effectively solved using a direct approach involving user input and formula application.

Using User Input to Calculate Area and Perimeter

This approach involves prompting the user to enter the length and width of the rectangle, then applying the standard formulas to calculate and display the area and perimeter.

// Rectangle Area and Perimeter Calculator
#include <iostream> // Required for input/output operations

int main() {
    // Step 1: Declare variables to store length, width, area, and perimeter
    // Using 'double' for precision to handle decimal values
    double length;
    double width;
    double area;
    double perimeter;

    // Step 2: Prompt the user to enter the length
    std::cout << "Enter the length of the rectangle: ";
    std::cin >> length; // Read the length from user input

    // Step 3: Prompt the user to enter the width
    std::cout << "Enter the width of the rectangle: ";
    std::cin >> width; // Read the width from user input

    // Step 4: Calculate the area using the formula: Area = Length * Width
    area = length * width;

    // Step 5: Calculate the perimeter using the formula: Perimeter = 2 * (Length + Width)
    perimeter = 2 * (length + width);

    // Step 6: Display the calculated area
    std::cout << "Area of the rectangle: " << area << std::endl;

    // Step 7: Display the calculated perimeter
    std::cout << "Perimeter of the rectangle: " << perimeter << std::endl;

    return 0; // Indicate successful execution
}

Run

Sample Output

Enter the length of the rectangle: 10.5
Enter the width of the rectangle: 4
Area of the rectangle: 42
Perimeter of the rectangle: 29

Stepwise Explanation

1. Include Header: The #include line brings in the necessary library for std::cout (output) and std::cin (input).
2. Declare Variables: double length, width, area, perimeter; declares four variables of type double. double is chosen to allow for measurements that include decimal points, providing more accurate results.
3. Get Input (Length): std::cout << "Enter the length of the rectangle: "; displays a message to the user. std::cin >> length; then waits for the user to type a number and press Enter, storing that number in the length variable.
4. Get Input (Width): Similarly, the program prompts for and reads the width.
5. Calculate Area: area = length * width; computes the area using the multiplication operator and stores the result in the area variable.
6. Calculate Perimeter: perimeter = 2 * (length + width); calculates the perimeter. The parentheses ensure that length + width is evaluated first, before being multiplied by 2. The result is stored in the perimeter variable.
7. Display Results: std::cout << "Area of the rectangle: " << area << std::endl; and std::cout << "Perimeter of the rectangle: " << perimeter << std::endl; print the calculated values to the console, each on a new line (std::endl).
8. Return 0: return 0; signifies that the program has executed successfully.

Conclusion

This article demonstrated how to create a simple yet effective C++ program to calculate the area and perimeter of a rectangle. By taking user input and applying basic arithmetic operations, we can automate these common geometric calculations. This serves as a foundational example for understanding C++ variables, input/output, and mathematical operations.

Summary

• The area of a rectangle is calculated as Length × Width.
• The perimeter of a rectangle is calculated as 2 × (Length + Width).
• C++ programs use std::cin for user input and std::cout for displaying results.
• Using double for length, width, area, and perimeter variables ensures precision when dealing with non-integer measurements.
• This basic program highlights fundamental C++ concepts such as variable declaration, user interaction, and arithmetic operations.