Learn to Program with Small Basic

Small Basic automatically indents
If statements as you type the code. This
makes the program easier to read and
clearly shows when statements are part
of code blocks. If your code ever gets unindented,
right-click in the Editor and
select Format Program from the pop-up
menu to indent all your code. Awesome!
The If statement is the basis of all
decision making in Small Basic. Check
out the illustration in Figure 8-1 to
understand how it works.
The condition of an If statement is
a logical expression (also called a Boolean
expression or a conditional expression) that’s
either true or false. If the condition is
Is
condition
true?
true, the program runs the statements between the If and EndIf keywords
(which is called the body of the If statement). But if the condition is false,
the statements in the block are skipped. The program runs the statement
after the EndIf keyword whether the condition is true or not.
No
Statement
after EndIf
Yes
Execute
statement(s)
between the
If and EndIf
keywords
Figure 8-1: The flowchart of the
If/Then/EndIf block
Tip
You can think of an If statement as a detour in the flow of a program. It’s like an
optional roller coaster loop.
Booleans in the Real World
The word Boolean is used in honor of George Boole, a 19th-century British
mathematician who invented a system of logic based on just two values: 1 and
0 (or true and false). Boolean algebra eventually became the basis for modernday
computer science.
In real life, we use Boolean expressions all the time to make decisions.
Computers also use them to determine which branch of a program to follow. A
remote server may grant or deny access when you swipe your credit card at a
department store based on whether your card was valid (true) or invalid (false).
A computer in a vehicle will automatically deploy the airbags when it decides
that a collision has occurred (collision = true). Your cell phone may display
a warning icon when the battery is low (batteryLow = true) and remove the
icon when the battery’s charge is acceptable (batteryLow = false).
These are just few examples of how computers cause different actions to
be taken by checking the results of Boolean conditions.
Making Decisions with If Statements 99