Page 177 - Learn To Program With Scratch

7

r e Pe t i t ion: a De e Pe r
e x PL or at ion of L oo P S

You’ve seen some of Scratch’s repetition structures
before, but this chapter covers them in greater detail.
It’s time to discuss new blocks that create loops, nested
loops, and recursion. By the end of this chapter, we’ll

have explored the following programming concepts:

• Repetition structures to execute statements repeatedly
• How to validate user input
• Counter-controlled and event-controlled loops
• Procedures that can call themselves with recursion
Although most people find repetitive tasks boring, computers seem to
like nothing more. Repetition structures, better known as loops, are program-
ming commands that tell a computer to repeatedly execute a statement or
a sequence of statements. The simplest kind of loop is a definite loop, which
repeats a sequence of statements a specific number of times. These loops

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