Professional

CHAPTER 4
Using decision statements
After completing this chapter, you will be able to:
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Declare Boolean variables.
Use Boolean operators to create expressions whose outcome is either true or false.
Write if statements to make decisions based on the result of a Boolean expression.
Write switch statements to make more complex decisions.
Chapter 3, “Writing methods and applying scope,” shows how to group related statements into
methods. It also demonstrates how to use parameters to pass information to a method and how to
use return statements to pass information out of a method. Dividing a program into a set of discrete
methods, each designed to perform a specific task or calculation, is a necessary design strategy. Many
programs need to solve large and complex problems. Breaking up a program into methods helps you
to understand these problems and focus on how to solve them, one piece at a time.
The methods in Chapter 3 are very straightforward, with each statement executing sequentially
after the previous statement completes. However, to solve many real-world problems, you also need
to be able to write code that selectively performs different actions and that takes different paths
through a method depending on the circumstances. In this chapter, you’ll learn how to accomplish
this task.
Declaring Boolean variables
In the world of C# programming (unlike in the real world), everything is black or white, right or
wrong, true or false. For example, if you create an integer variable called x, assign the value 99 to it,
and then ask whether x contains the value 99, the answer is definitely true. If you ask if x is less than
10, the answer is definitely false. These are examples of Boolean expressions. A Boolean expression
always evaluates to true or false.
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