Learn to Program with C_ Learn to Program using the Popular C Programming Language ( PDFDrive )

Chapter 4 ■ Programs with Selection Logic
The latest C99 standard defines the type bool. However, in this book, we will use the traditional
approach mainly because many popular C compilers do not support the C99 standard as yet. Also,
as you will see, we can easily live without bool. The vast majority of our Boolean expressions would
be relational expressions used in if and while statements. If we ever need a “Boolean” variable, we
can use an int variable with 1 representing true and 0 representing false.
4.3 The if Construct
Let us write a program for the following problem:
A computer repair shop charges $100 per hour for labor plus the cost of any parts used in the
repair. However, the minimum charge for any job is $150. Prompt for the number of hours worked
and the cost of parts (which could be $0) and print the charge for the job.
We will write the program so that it works as follows:
Hours worked? 2.5
Cost of parts? 20
Charge for the job: $270.00
or
Hours worked? 1
Cost of parts? 25
Charge for the job: $150.00
The following algorithm describes the steps required to solve the problem:
prompt for and read the hours worked
prompt for and read the cost of parts
calculate charge = hours worked * 100 + cost of parts
if charge is less than 150 then set charge to 150
print charge
This is another example of an algorithm written in pseudocode—an informal way of specifying
programming logic.
The algorithm introduces a new statement—the if statement. The expression
charge is less than 150
is an example of a condition. If the condition is true, the statement after then (called the then part)
is executed; if it is false, the statement after then is not executed.
Program P4.1 shows how to express this algorithm as a C program.
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