Visual Basic.NET How to Program (PDF)

186 Procedures Chapter 6
11 PrintPay(20, 13)
12 PrintPay(50, 14)
13
14 End Sub ' Main
15
16 ' print dollar amount earned in command window
17 Sub PrintPay(ByVal hours As Double, ByVal wage As Decimal)
18
19 ' pay = hours * wage
20 Console.WriteLine("The payment is {0:C}", hours * wage)
21 End Sub ' PrintPay
22
23 End Module ' modPayment
The payment is $420.00
The payment is $826.50
The payment is $260.00
The payment is $700.00
Fig. Fig. Fig. 6.2 6.2 6.2 Sub procedure for printing payment information (part 2 of 2).
The program contains two procedure definitions. Lines 6–14 define Sub procedure
Main, which executes when the console application is loaded. Lines 17–21 define Sub
procedure PrintPay, which executes when it is invoked, or called, from another procedure,
in this case Main.
Main makes four calls (lines 9–12) to Sub procedure PrintPay, causing
PrintPay to execute four times. Although the procedure arguments in this example are
constants, arguments can also be variables or expressions. For example, the statement
PrintPay(employeeOneExtraHours, employeeOneWage * 1.5)
could be used to display payment information for an employee who is being paid time-anda-half
for working overtime.
When Main calls PrintPay, the program makes a copy of the value of each argument
(e.g., 40 and 10.5 on line 9), and program control transfers to the first line of procedure
PrintPay. Procedure PrintPay receives the copied values and stores them in
the parameter variables hours and wage. Then, PrintPay calculates hours * wage
and displays the result, using the currency format (line 20). When the End Sub statement
on line 21 is encountered, control is returned to the calling procedure, Main.
The first line of procedure PrintPay (line 17) shows (inside the parentheses) that
PrintPay declares a Double variable hours and a Decimal variable wage. These
parameters hold the values passed to PrintPay within the definition of this procedure.
Notice that the entire procedure definition of PrintPay appears within the body of
module modPayment. All procedures must be defined inside a module or a class.
The format of a procedure definition is
Sub procedure-name(parameter-list)
declarations and statements
End Sub