**C program to calculate area, perimeter and diagonal of a rectangle** has been given below. Suppose, length and breadth of a rectangle are *l* unit, and *b* unit respectively. Then area, perimeter and diagonal of that rectangle would be *l * b* unit^2, *2 * (l + b)* unit and *sqrt(l^2 + b^2)* unit, respectively.

For example, if length is 7 cm and breadth is 3 cm, then area of the rectangle would be 7 * 3 = 21 cm^2 while perimeter and diagonal would be 2 * (7 + 3) = 20 cm and sqrt(7^2 + 3^2) = sqrt(58) = 7.616 cm.

The algorithm, pseudocode, and time-complexity of the program have also been covered below.

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

1. Take the length *l* and the breadth *b* of a rectangle as inputs.

2. Compute *a = l * b*

3. Compute *p = 2 * (l + b)*

4. Compute *d = sqrt(l^2 + b^2)*

5. Declare the *a* as the area, *p* as the perimeter and *d* as the diagonal of that rectangle.

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

**Input** : Length *l* and breadth *b* of a rectangle

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

1. **Procedure** areaPerimeterDiagonal(*l, w*):

2. *A := l * b*

3. *P := 2 * (l + b)*

4. *D := sqrt(l^2 + b^2)*

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

6. **End Procedure**

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

**Time Complexity: O(1)**

## 4. C Program & Output to calculate area, perimeter and diagonal of a rectangle

/************************************* alphabetacoder.com C program to calculate the area, perimeter and diameter of a rectangle **************************************/ #include <stdio.h> #include <math.h> int main() { // declare variables float l, b, a, p, d; // take input printf("Enter the length of rectangle: "); scanf("%f", & l); printf("Enter the breadth of rectangle: "); scanf("%f", & b); // calculate area a = l * b; // calculate perimeter p = 2 * (l + b); // calculate diagonal d = sqrt(l * l + b * b); // display result upto 3 decimal places printf("Area: %0.3f\n", a); printf("Perimeter: %0.3f\n", p); printf("Diagonal: %0.3f\n", d); return 0; }

Output

Enter the length of rectangle: 10.5

Enter the breadth of rectangle: 7

Area: 73.500

Perimeter: 35.000

Diagonal: 12.619