C Program to Find the Area and Perimeter of a Rectangle

If you’ve ever measured a room to fit a carpet or frame, you've worked with rectangles. Finding a rectangle's area and perimeter isn’t tough. This C program gets the rectangle's length and width and calculates both values for you.

This can be super handy in real life. Let’s see how to do it with C.

Prerequisites for Calculating Area and Perimeter in C

Before coding, ensure you know the following:

• Usage of int data types for variables like length and width.
• Basic arithmetic operators: * for multiplication, +, and * again for the perimeter formula.
• Any C compiler such as GCC 9 or newer — or just run it in the EduSeekho online compiler.

Source Code of C Program to Find the Area and Perimeter of a Rectangle

Here's the complete C code that calculates the area and perimeter of a rectangle based on input values.

#include <stdio.h>

int main() {
    int length, width, area, perimeter;
    // Input length and width
    printf("Enter the length of the rectangle: ");
    scanf("%d", &length);
    printf("Enter the width of the rectangle: ");
    scanf("%d", &width);
    // Compute area and perimeter
    area = length * width;
    perimeter = 2 * (length + width);
    // Output area and perimeter
    printf("Area of the rectangle = %d\n", area);
    printf("Perimeter of the rectangle = %d\n", perimeter);
    return 0;
}

Output of the Area and Perimeter Program

Once you run the program and provide the inputs, it displays the results as shown below.

Enter the length of the rectangle: 5
Enter the width of the rectangle: 3
Area of the rectangle = 15
Perimeter of the rectangle = 16

Algorithm to Calculate Area and Perimeter in C

Calculating a rectangle's area and perimeter involves multiplying its dimensions and using simple arithmetic. Here's the step-by-step logic the program follows:

1. Start the program.
2. Read the rectangle's length and width from the user.
3. Calculate the area as length * width.
4. Calculate the perimeter as 2 * (length + width).
5. Print the area and perimeter.
6. End the program.

flowchart TD
  A([Start]) --> B[/Read length and width/]
  B --> C[area = length * width]
  C --> D[perimeter = 2 * (length + width)]
  D --> E[/Print area and perimeter/]
  E --> F([End])

How the C Program for Area and Perimeter Works

Let's walk through how the program works line by line:

• Includes the <stdio.h> library to use the printf and scanf functions.
• The main function defines int variables for length, width, area, and perimeter.
• Prompts the user to enter the rectangle's length and stores it in length.
• Prompts for the width and stores it in width.
• Calculates the area using length * width and assigns it to area.
• Calculates the perimeter using 2 * (length + width) and assigns it to perimeter.
• Prints both the area and perimeter with explanatory strings.
• Ends the program with return 0.

Time and Space Complexity of the C Program

This program's efficiency is straightforward given the computations involved.

Time Complexity: O(1). The program executes a fixed number of operations regardless of input values. It reads two inputs and performs two calculations, so it always runs in the same time.

Space Complexity: O(1). The program uses four int variables: length, width, area, and perimeter. Their count doesn't change with different inputs.

Key takeaway: Knowing formulas is key for accurate programming, especially in geometry.

FAQs About C Program to Find the Area and Perimeter

Students often have specific questions about calculating area and perimeter. Here are some common ones:

Related Programs

If you found this program helpful, check out these related programs:

• C Program to Calculate Simple and Compound Interest
• C Program to Calculate Difference Between Two Time Periods
• C Program to Calculate Area and Circumference of Circle
• C Program to Find the Roots of a Quadratic Equation
• C Program to Calculate Standard Deviation — Full Code & Output

Conclusion

Geometry calculations like these pop up a lot. If you ever need to calculate other shapes, knowing how C handles these basics is super useful. Next time, try working with circles.

Practice more C programs to really nail this down. Check out more exercises in our C quiz or jump back to coding with the C compiler.