Computer Programming Concepts and Visual Basic David I. Schneider

’Determine amount of data to be processed
numStudents = 0
Open “SCORES.TXT” For Input As #1
Do While Not EOF(1)
Input #1, nTemp, sTemp
numStudents = numStudents + 1
Loop
Close #1
‘Create arrays for names and scores
ReDim nom(1 To numStudents) As String, score(1 To numStudents) As Integer
Open “SCORES.TXT” For Input As #1
For student = 1 To numStudents
Input #1, nom(student), score(student)
Next student Close #1
‘Analyze exam scores
total = 0
For student = 1 To numStudents
total = total + score(student)
Next student
average = total / numStudents
‘Display all names with above-average grades
picTopStudents.Cls
For student = 1 To numStudents
If score(student) > average Then
picTopStudents.Print nom(student)
End If
Next student
End Sub
An alternative approach to program flexibility that does not require reading the data file twice
is to require that the data file begin with a line that holds the number of records to be processed.
If SCORES.TXT is modified by adding a new first line that gives the number of students,
then the fourth through eighteenth lines of Example 4 can be replaced with
’Create arrays for names and scores
Open “SCORES.TXT” For
Input As #1
Input #1, numStudents
ReDim nom(1 To numStudents) As String, score(1 To numStudents) As Integer
For student = 1 To numStudents
Input #1, nom(student), score(student)
Next student
Close #1
In Example 4, the ReDim statement allowed us to create arrays whose size was not
known before the program was run. On the other hand, the arrays that were created were local
to the event procedure cmdShow_Click. Many applications require form-level arrays whose
size is not known in advance. Unfortunately, Dim statements cannot use variables or expressions
to specify the subscript range. The solution offered by Visual Basic is to allow the
(Declarations) section of (General) to contain Dim statements of the form
Dim arrayName() As varType
Creating and Accessing Arrays 167
where no range for the subscripts of the array is specified. An array created in this manner will
be form-level but cannot be used until a ReDim statement is executed in a procedure to establish
the range of subscripts. The “As varType” clause can be omitted from the ReDim statement.