8.1 Nested Loops
So far our loops have been straight forward. We saw examples of individual loops: pre-test, and post-test, pseodocode and C++ code. And we developed some projects that used the techniques illustrated in the examples. Programming in the real world, however, is seldom so simple. There are many situations requiring nested loops, where we find one loop structure embedded inside another. We will also see nested selection structures embedded in an embedded loop, but that comes later. You are now familiar with the three basic structures necessary to write any program: sequential, selection, and repetition. From now on most of our work will examine how to combine these structures into more and more complex structures. This is similar to the way we learn natural languages. We generally start with words, develop simple sentences, then compound and complex sentences. We then learn how to join sentences into paragraphs using key words to add coherence to our text, and so on. We are doing the same when we learn and eventually master a programming language. We now know the necessary structures and must learn to combine them into meaningful code to solve complex problems. We start with nested loops.
Using any of the techniques we have just learned, try to write a multiplication table for the numbers 1 through 10. Your program should create a table similar to the following:
1 2 3 4 5 6 7 8 9 10
2 4 6 8 10 12 14 16 18 20
3 6 9 12 15 18 21 24 27 30
4 8 12 16 20 24 28 32 36 40
... lines 5-9 skipped to save space
10 20 30 40 50 60 70 80 90 100
Here is the code to generate any of the 10 rows based on user input:
Start
Declare: number, counter counter = 1
Write "Enter a number between 1 and 10: "
Read number
While counter