Computer Programming Concepts and Visual Basic David I. Schneider

■ CONTROL BREAK PROCESSING
Suppose a small real estate company stores its sales data for a year in a sequential file in which
each record contains four fields: month of sale, day of sale (1 through 31), address, and price.
Typical data for the sales of the first quarter of a year are shown in Figure 7-2. The records are
ordered by date of sale.
Month Day Address Price
January 9 102 Elm Street $203,000
January 20 1 Main Street $315,200
January 25 5 Maple Street $123,450
February 15 1 Center Street $100,000
February 23 2 Vista Drive $145,320
March 15 205 Rodeo Circle $389,100
FIGURE 7-2 Real Estate Sales for First Quarter of Year
Figure 7-3 shows the output of a program that displays the total sales for the quarter year,
with a subtotal for each month.
FIGURE 7-3 Output of Example 3
A program to produce the output of Figure 7-3 must calculate a subtotal at the end of
each month. The variable holding the month triggers a subtotal whenever its value changes.
Such a variable is called a control variable and each change of its value is called a break.
EXAMPLE 3
The following program produces the output of Figure 7-2. The data of Figure 7-2 are stored in the sequential
file HOMESALE.TXT. The program allows for months with no sales. Because monthly subtotals will
be printed, the month-of-sale field is an appropriate control variable.
Private Sub cmdCreateReport_Click()
Dim currentMonth As String, newMonth As String
Dim dayNum As Integer, address As String
Dim price As Single, monthTotal As Single
Dim yearTotal As Single, doneFlag As Boolean
‘Display home sales by month
picReport.Cls
Open “HOMESALE.TXT” For Input As #1
currentMonth = “” ‘Name of month being subtotaled
monthTotal = 0
yearTotal = 0
doneFlag = False ‘Flag to indicate end of list
Do While Not doneFlag
Using Sequential Files 227