programming-for-dummies

Picking Three or More Choices with the IF-THEN-ELSEIF Statement 185
command #2
.
.
command #3
)
The IF-THEN-ELSE statement tells the computer, “Check if something is
True. If so, follow this set of commands. Otherwise, follow this second set of
commands.”
One problem with the IF-THEN-ELSE statement is that it only checks a
single condition. If that single condition is False, it always runs its second
set of commands, such as
IF (Salary > 100000) THEN
TaxRate = 0.45
ELSE
TaxRate = 0.30
END IF
In this BASIC language example, if the value of the Salary variable is greater
than 100000, the TaxRate variable is always set to 0.45.
Book II
Chapter 4
Making Decisions
by Branching
However, if the Salary variable isn’t greater than 100000 (it’s less than or
equal to 100000), the ELSE portion of the IF-THEN-ELSE statement always
sets the TaxRate variable to 0.30.
The IF-THEN-ELSE always gives the computer a choice of exactly two,
mutually exclusive choices. What if you want to give the computer three or
more possible choices? Then you must use the IF-THEN-ELSEIF statement.
Picking Three or More Choices with
the IF-THEN-ELSEIF Statement
The IF-THEN-ELSEIF statement offers two advantages over the IF-THEN-
ELSE statement:
✦ You can check a condition for each set of commands.
✦ You can define three or more separate sets of commands for the computer
to follow.
Not all programming languages, such as C/C++, offer the IF-THEN-ELSEIF
statement.