C++ switch..case Statement

In this tutorial, we will find out about the switch statement and its working in C++ programming with the help of certain examples.

The switch statement allows us to execute a block of code among many other options.

The syntax of the switch statement in C++ is:

switch (expression)  {
    case constant1:
        // code to be executed if 
        // expression is equal to constant1;
        break;

    case constant2:
        // code to be executed if
        // expression is equal to constant2;
        break;
        .
        .
        .
    default:
        // code to be executed if
        // expression doesn't match any constant
}

How does the switch statement work?

The expression is evaluated once and contrasted and the values of each case label.

If there is a match, the relating code after the coordinating name is executed. For instance, if the value of the variable is equivalent to constant2, the code after case constant2: is executed until the break statement is encountered.

If there is no match, the code after default: is executed.

Note: We can do something very similar with the if…else..if ladder. However, the syntax of the switch statement is cleaner and much easier to read and write.

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Example: Create a Calculator using the switch Statement

// Program to build a simple calculator using switch Statement
#include <iostream>
using namespace std;

int main() {
    char oper;
    float num1, num2;
    cout << "Enter an operator (+, -, *, /): ";
    cin >> oper;
    cout << "Enter two numbers: " << endl;
    cin >> num1 >> num2;

    switch (oper) {
        case '+':
            cout << num1 << " + " << num2 << " = " << num1 + num2;
            break;
        case '-':
            cout << num1 << " - " << num2 << " = " << num1 - num2;
            break;
        case '*':
            cout << num1 << " * " << num2 << " = " << num1 * num2;
            break;
        case '/':
            cout << num1 << " / " << num2 << " = " << num1 / num2;
            break;
        default:
            // operator is doesn't match any case constant (+, -, *, /)
            cout << "Error! The operator is not correct";
            break;
    }

    return 0;
}

Output 1

Enter an operator (+, -, *, /): +
Enter two numbers: 
2.3
4.5
2.3 + 4.5 = 6.8

Output 2

Enter an operator (+, -, *, /): -
Enter two numbers: 
2.3
4.5
2.3 - 4.5 = -2.2

Output 3

Enter an operator (+, -, *, /): *
Enter two numbers: 
2.3
4.5
2.3 * 4.5 = 10.35

Output 4

Enter an operator (+, -, *, /): /
Enter two numbers: 
2.3
4.5
2.3 / 4.5 = 0.511111

Output 5

Enter an operator (+, -, *, /): ?
Enter two numbers: 
2.3
4.5
Error! The operator is not correct.

In the above program, we are using the switch…case statement to perform addition, subtraction,multiplication, and division.

How This Program Works

Notice that the break statement is used inside each case square. This ends the switch statement.

If the break statement isn’t used, all cases after the right case are executed.

1. We first prompt the user to enter the desired operator. This input is then stored in the char variable named oper.

2. We at that point prompt the user to enter two numbers, which are stored in the float variables num1 and num2.

3. The switch statement is then used to check the operator entered by the user:
If the user enters +, addition is performed on the numbers.
If the user enters -, subtraction is performed on the numbers.
If the user enters *, multiplication is performed on the numbers.
If the user enters /, the division is performed on the numbers.
If the user enters any other character, the default code is printed.

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Please feel free to give your comment if you face any difficulty here.

C++ Flow Control