**C# program to calculate the area, perimeter and diagonal of a square** has been given below. If length of the side of a square is $s~ unit$, the area, perimeter and diagonal of that square would be $s^2~\text{unit}^2$, $4s~\text{unit}$ and $s\sqrt{2}~\text{unit}$ respectively.

For example, if length of the side of a square is $5~cm$, the area would be $5^2 = 25~\text{cm}^2$ while the perimeter would be $4 \cdot 5 = 20~\text{cm}$. The diagonal will be calculated as $5\cdot \sqrt{2} = 7.071 ~\text{cm}$

In the following section, the algorithm, pseudocode and time-complexity of the program have also been covered.

## 1. Algorithm to calculate the area, perimeter and diagonal of a square

1. Take the length of side $s$ as input.

2. Declare $s^2$ as the area of the square

3. Declare $4s$ as the perimeter of the square

4. Declare $s\sqrt{2}$ as the diagonal of the square

## 2. Pseudocode to calculate the area, perimeter and diagonal of a square

**Input** : Length of side $s$

**Output** : Area $A$, Perimeter $P$ and Diagonal $D$ of the square

1. **Procedure** areaPerimeterDiagonal($s$):

2.

3.

4.

5. **Return** $A, P, D$

6. **End Procedure**

## 3. Time complexity to calculate the area, perimeter and diagonal of a square

**Time Complexity: O(1)**

## 4. C# Program to calculate the area, perimeter and diagonal of a square

/************************************** alphabetacoder.com C# program to calculate the area ,perimeter and diagonal of a square ***************************************/ using System; namespace AreaPerimeterDiagonal { class Program { static void Main(string[] args) { //declare variables double s, a, p, d; // take input Console.Write("Enter the length of side of the square: "); s = Convert.ToDouble(Console.ReadLine()); // calculate area a = s * s; // calculate perimeter p = 4 * s; // calculate diagonal d = s * Math.Sqrt(2); // display result upto 3 decimal places Console.Write("Area: " + string.Format("{0:0.000}", a) + "\n"); Console.Write("Perimeter: " + string.Format("{0:0.000}", p) + "\n"); Console.Write("Diagonal: " + string.Format("{0:0.000}", d) + "\n"); // wait for user to press any key Console.ReadKey(); } } }

Output

Enter the length of side of the square: 5

Area: 25.000

Perimeter: 20.000

Diagonal: 7.071

- The program calculates the area, perimeter, and diagonal of a square based on the length of its sides.
- Four float variables are declared:

**s**: Stores the length of the side of the square.**a**: Will store the area of the square.**p**: Will store the perimeter of the square.**d**: Will store the diagonal of the square. - The program prompts the user to enter the length of the side of the square.
- It reads the user's input and stores it in the variable
**s**. - The program calculates the area of the square by squaring the side length (
**s * s**), the perimeter by multiplying the side length by 4 (**4 * s**), and the diagonal by multiplying the side length by the square root of 2 (**s * sqrt(2)**). - The calculated area, perimeter, and diagonal values are then displayed on the screen. They are formatted to show up to three decimal places.