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OBJECTIVES

Many new programs need to read and write data to disk files. This lesson is geared toward learning how to create these files, how to read data from these files, and how to write data to files. VB uses three methods to access files: 1) Random access; 2) Sequential access; and 3) Binary access.

ACCESSING FILES

1.  Assuming that there is a user-defined data type that is defined 
as follows:

    Type EmployeeInfo
         Name     As String * 40
         Age      As Integer 
    End Type

What does the following code do?

    Dim FileNum As Integer
    Dim Employee As EmployeeInfo

    FileNum = FreeFile
    Open "EMPLOYEE.DAT" For Random As FileNum Len =
    Len(PersonInfo)
    Employee.Name = "JOHN SMITH"
    Employee.Age = 32
    Put FileNum, 5, Employee

2.  Assuming that there is a user-defined data type that is defined as 
follows:

    Type EmployeeInfo
        Name     As String * 40
        Age      As Integer
    End Type

What does the following code do?

    Dim FileNum As Integer
    Dim Employee As EmployeeInfo

    FileNum = FreeFile
    Open "EMOLOYEE.DAT" For Random As FileNum Len = 
    Len(Employee)
    
3.  What does the following code do?

    FileNum = FreeFile
    Open "TRY>TXT" For Output As FileNum
    Print #FileNum, txtMyText.Text
    Close FileNum

4.  What do the following statements do?

    FileNum = FreeFile
    Open "C:\TRY\TRY.TXT" For Apppend As FileNum

5.  What does the following code do?

    FileNum = Free File
    Open "INFO>TXT" For Append As FileNum
    txtMyText.Text = Input$(LOF(FileNum), FileNum)
    Close FileNum

6.  What does the following code do?

    FileNum = FreeFile
    Open "INFO>TXT" For Append As FileNum
    Print #FileNum, txtMyText.Text
    Close FileNum

7.  What does the following code do?
  
    FileNum = FreeFile
    Open "TRY.DAT" For Binary As FileNum
    MyString = "THIS IS A TEST!"
    Put #FileNum, 75, MyString

8.  What does the following code do?

    FileNum = FreeFile
    Open "TRY.DAT" For Binary as FileNum
    MyString = String$(20, "")
    Get #FileNum, 75, MyString
    MsgBox "MyString=" +MyString
    Close FileNum

TEST YOUR PROGRESS

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