Learn to Program with Small Basic

TRY IT OUT 4-3
Write a program that evaluates the following expression. Try taking a couple different
approaches. Try doing it while dancing! Don’t be shy!
1 + 7
9 8
1 + 6
5 7
Using Variables to Solve Problems
People often solve problems without really thinking through every step of
the process. But computers can’t do this: they need you to think through
each step for them (at least until The Terminator or The Matrix come true).
That’s why it takes some planning to use a computer to solve a problem.
When developing a solution to a programming problem, you should do this:
1. Understand what the problem is.
2. Design a solution.
3. Write the program.
4. Test the program to make sure it works as you expect it to.
Let’s say you want to create a program that computes the area of a circle
with a given radius. To solve the problem, you need to answer these basic
questions:
1. What do you need the program to output?
2. What input do you need, and where will the program get this input from?
3. What processing will the program have to do to turn the input into the
output?
For this problem, here’s how you’d answer those questions:
1. Your program needs to output the area of a circle. It’ll show this output
to the user in the text window.
2. This program needs a single input from your user: the radius of the
circle.
3. Your program will need to compute the area using this formula, which
might be familiar from math class:
area = π × (radius) 2
Note
The Greek letter π, pronounced pi, is a special number that can be rounded to
3.1416. We gave you free pi!
Using Variables 51