Computer Programming Concepts and Visual Basic David I. Schneider

50 Computer Programming Concepts and Visual Basic
EXAMPLE 1
Write a program that uses a file for input and produces the same output as the following code. (The form
design for all examples in this section consists of a command button and a picture box.)
Private Sub cmdDisplay_Click()
Dim houseNumber As Single, street As String
picAddress.Cls
houseNumber = 1600
street = “Pennsylvania Ave.”
picAddress.Print “The White House is located at”; houseNumber; street
End Sub
[Run and then click the command button. The following is displayed in the picture box.]
The White House is located at 1600 Pennsylvania Ave.
SOLUTION:
Use Windows’ Notepad to create the file DATA.TXT containing the following two lines:
1600
“Pennsylvania Ave.”
In the following code, the fifth line looks for the first item of data, 1600, and assigns it to the numeric
variable houseNumber. (Visual Basic records that this piece of data has been used.) The sixth line looks
for the next available item of data, “Pennsylvania Ave.”, and assigns it to the string variable street. Note:
You will have to alter the Open statement in the fourth line to tell it where the file DATA.TXT is located.
For instance, if the file is in the root directory (that is, folder) of a diskette in drive A, then the line should
read Open “A:\DATA.TXT” For Input As #1. If the file is located in the subdirectory (that is,
folder) VB6 of the C drive, then the statement should be changed to Open ”C:\VB6\DATA.TXT”
For Input As #1. See Comment 1 for another option.
Private Sub cmdReadFile_Click()
Dim houseNumber As Single, street As String
picAddress.Cls
Open “DATA.TXT” For Input As #1
Input #1, houseNumber
Input #1, street
picAddress.Print “The White House is located at”; houseNumber; street
Close #1
End Sub
A single Input # statement can assign values to several different variables. For instance,
the two Input # statements in the solution of Example 1 can be replaced by the single statement
Input #1, houseNumber, street
In general, a statement of the form
Input #n, var1, var2, ..., varj
has the same effect as the sequence of statements
Input #n, var1
Input #n, var2
.
.
.
Input #n, varj