Loops: Don't Repeat Yourself

Imagine telling a computer to print "Happy Birthday" 100 times. Writing it 100 times would be silly — so we use a loop: an instruction that says "repeat this a certain number of times" (or "repeat until something happens"). Loops let a few lines of code do a huge amount of work, which is one of the reasons computers are so powerful. But beware the infinite loop — a loop with no way to stop will run forever and freeze the program. A good loop always has a clear ending condition: "repeat 10 times," or "repeat until the score reaches 100."