Computer Programming Concepts and Visual Basic David I. Schneider

Some of the benefits of documentation are as follows:
1. Other people can easily comprehend the program.
2. The program can be understood when read later.
3. Long programs are easier to read because the purposes of individual pieces can
be determined at a glance.
COMMENTS
1. Visual Basic provides a convenient device for accessing a file that resides in the
same folder as the (saved) program. After a program has been saved in a folder,
the value of App.Path is the string containing the name of the folder. Therefore,
if a program contains a line such as
Open App.Path & “\DATA.TXT” For Input As #1
Visual Basic will look for the file DATA.TXT in the folder containing the program.
The programs from this book, as well as the data files they use, all are contained
in the folder Programs on the CD accompanying this book. On the CD,
App.Path is used in every Open statement. Therefore, even after you copy the
contents of the Programs folder onto a hard drive or diskette, the programs will
continue to execute properly without your having to alter any paths.
2. The text box and input box provide a whole new dimension to the capabilities
of a program. The user, rather than the programmer, can provide the data to be
processed.
3. A string used in a file does not have to be enclosed by quotation marks. The
only exceptions are strings containing commas or leading and trailing spaces.
4. If an Input # statement looks for a string and finds a number, it will treat the
number as a string. Suppose the first two entries in the file DATA.TXT are the
numbers 2 and 3.
Private Sub cmdButton_Click()
Dim a As String, b As String
picBox.Cls
Open “DATA.TXT” For Input As #1
Input #1, a, b
picBox.Print a + b
Close #1
End Sub
[Run and then click the command button. The following is displayed in the picture
box.]
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5. If an Input # statement looks for a number and finds a string, the Input # statement
will assign the value 0 to the numeric variable. For instance, suppose the
first two entries in the file DATA.TXT are “ten” and 10. Then after the statement
Input #1, num1, num2
is executed, where um1 and num2 are numeric variables, the values of these
variables will be 0 and 10.
Input and Output 57