Switch structure

The switch structure is used when one wants to check the equality of a variable or expression against a list of values (constants).

General syntax:

switch(expression):
{
    case constant1:
        break;
    case constant2:
        break;
    default:
        break;
}

Where expression can take the values: constant1, constant2 or other value in which case the default branch will be executed. The expression must be evaluated at an integer, enumerated value or character.

First practical example:

#include <iostream>
int main()
{
    int value = 0;

    std::cout << "Please enter your grade from the math test you took yesterday (between 1 (worst) and 5 (best)): " << std::endl;
    std::cin >> value;
    switch(value)
    {
        case 1:
            std::cout << "Lame!" << std::endl;
            break;
        case 2:
            std::cout << "Keep learning!" << std::endl;
            break;
        case 3:
            std::cout << "You did good!" << std::endl;
            break;
        case 4:
            std::cout << "Very good!" << std::endl;
            break;
        case 5:
            std::cout << "In the zone!" << std::endl;
            break;
        default:
            std::cout << "Please enter an integer between 1 and 5!" << std::endl;
            break;
    }
}

Second practical example:

#include <iostream>
int main()
{
    char firstLetter = 'x';

    std::cout << "Please enter the first letter of the alphabet (uppercase letter): " << std::endl;
    std::cin >> firstLetter;
    switch(firstLetter)
    {
        case 'A':
            std::cout << "Correct!" << std::endl;
            break;
        case 'a':
            std::cout << "It is the first letter, but it is not uppercase letter!" << std::endl;
            break;
        default:
            std::cout << "Wrong value!" << std::endl;
            break;
    }
}

There can be any number of cases and the default case is optional, although it is a good practice to use the default statement to handle other situations. A good practice is to surround the code in a case with braces when the code from that case exceeds one line (like below):

...
case 'X':
{
    std::cout << "Begin long code... " << std::endl;
    if(a condition)
    {
    }
    else if(another condition)
    {
    }
    else
    {
    }
    std::cout << "End long code... " << std::endl;
}
break;
case 'Y':
...

When the variable being switched on is equal to a case, the statements following that case will execute until a break statement is reached.

When a break statement is reached, the switch terminates, and the flow of control jumps to the next line following the switch statement.

When the variable being switched on is equal to a case, the statements following that case will execute until a break statement is reached.

Practical example:

#include <iostream>
int main()
{
    char firstLetter = 'x';

    std::cout << "Please enter the first letter of the alphabet (uppercase letter): " << std::endl;
    std::cin >> firstLetter;
    switch(firstLetter)
    {
        case 'A':
            std::cout << "Correct!" << std::endl;
        case 'a':
            std::cout << "It is the first letter, but it is not uppercase letter!" << std::endl;
        default:
            std::cout << "Wrong value!" << std::endl;
    }
}

In the example above, all three cout statements are executed because no break is found.