Conditional Statements

Conditional statements let a program make decisions, running different code depending on whether an expression evaluates to true or false.

if, else if, and else

An if statement runs a block only when its condition is true. Chaining else if lets you check multiple conditions in order, and a final else catches anything not matched above.

int mark = 74;

if (mark >= 80) {
    std::cout << "Distinction" << std::endl;
} else if (mark >= 60) {
    std::cout << "Merit" << std::endl;
} else if (mark >= 50) {
    std::cout << "Pass" << std::endl;
} else {
    std::cout << "Fail" << std::endl;
}

The switch Statement

A switch is a clean alternative to a long else if chain when you are comparing one variable against several exact values. Each case must end with break;, or execution will fall through into the next case.

int day = 3;
switch (day) {
    case 1: std::cout << "Monday"; break;
    case 2: std::cout << "Tuesday"; break;
    case 3: std::cout << "Wednesday"; break;
    default: std::cout << "Invalid day";
}

Common Mistakes

• Forgetting break; in a switch case, causing execution to fall through into the next case.
• Using = instead of == inside an if condition, which assigns instead of compares.
• Writing conditions that overlap so an earlier else if always matches first, making later branches unreachable.
• Using a switch on a type it does not support, such as a std::string (switch only works on integral and enum types).