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Loops allow repeating the execution of a block of code as long as a condition remains true.

In C++, the standard loops are: for, while, and do-while.

The for Loop

The for loop is used when you know the number of iterations in advance:

// Prints numbers from 0 to 4
for (int i = 0; i < 5; ++i) {
    std::cout << i << " ";
}

The structure of the for loop is split into three parts separated by semicolons ;:

1. Initialization: run only once at the beginning (e.g. int i = 0).
2. Condition: evaluated before each iteration; if false, the loop ends (e.g. i < 5).
3. Update: run at the end of each iteration (e.g. ++i).

The while Loop

The while loop repeats the code as long as its condition is true. It is typically used when the number of iterations is not known beforehand:

int energy = 3;
while (energy > 0) {
    std::cout << "Energy: " << energy << std::endl;
    energy--; // Decrement to prevent an infinite loop
}

The do-while Loop

Unlike the while loop, the do-while loop guarantees that the body of the loop is executed at least once, because the condition is evaluated at the end:

int x = 10;
do {
    std::cout << "Executed!" << std::endl;
} while (x < 5); // Condition is false, loop terminates after the first iteration

Try it yourself