Loops

A loop is simply a way to repeat a block of code multiple times.

Types of loops

There are a few different types of loops, including:

• Count-controlled loops
• Condition-controlled loops
• Infinite loops

Count-controlled loops

A count-controlled loop repeats a block of code a specific number of times - e.g. by repeating it for each item in a collection, or by counting from one number to another.

The most common example is a for loop.

Condition-controlled loops

A condition-controlled loop repeats a block of code as long as a certain condition is true.

In pseudocode, we might write this as:

while (condition is true) {
    // Code to repeat
}

..and the Code to repeat will keep running until the condition becomes false.

Infinite loops

An infinite loop is a loop that never ends. This usually happens when the condition for a condition-controlled loop never becomes false.

An infinite loop is essentially the same as saying:

while (true) {
    // Code to repeat forever
}

(because the condition will never be false).

Often, infinite loops are a mistake - for example, if we forget to update a variable. But they do have uses!

Types of infinite loops

There are actually two types of infinite loops:

• actually infinite loops, which never end
• inifinite loops that we manually break out of

Actually infinite loops

These are infinite loops that actually never end. For example:

while (true) {
    Console.WriteLine("This will print forever!");
}

These are almost always a mistake, unless you’re writing something like an operating system or server that is supposed to run forever.

Infinite loops that we manually break out of

Using the break (or return) keyword (which we will cover soon!), we can create a while loop that, even though the condition never becomes false, we can still exit the loop when we want to.

For example:

while (true) {
    Console.WriteLine("Type 'exit' to quit the loop:");
    string input = Console.ReadLine();
    if (input == "exit") {
        break; // Exit the loop
    }
    Console.WriteLine("You typed: " + input);
}

In this example, the loop will keep running until the user types “exit”, at which point the break statement will exit the loop.