The document discusses file handling operations in Visual Basic. It defines a file as a collection of stored data and describes three types of files: sequential access, random access, and binary. It then explains various file handling operations like opening, closing, writing, reading and detecting the end of a file. It provides syntax for performing these operations and describes how to apply these concepts in a sample application for creating, appending to, reading from and writing to a file.

1. Presentation
on
File Handling

2. Contents
 Definition Of File
 Types Of Files
 Operations on File
 Opening A File
 Closing A File
 Writing Data To A File
 Reading Data From A File
 Detecting The End of File
 Storing A File
 Demo Application

3. Definition Of File
 A File is a collection of data stored on a
computer’s disk.
 Information can be saved to files and later
reused.

4. Types Of Files
 There are three types of files.
1) Sequential Access Files
2) Random Access Files
3) Binary Files

5. Sequential Access File
 A sequential access file is a stream of data that
must be read from its beginning to its end.
 To read a record that is stored in the middle or at
the end of sequential access file an application
must read all the records in the file before it.

6. Random Access File
 In Random access file Records must be identical
in length and may be accessed in any order.
 An application may immediately jump to any
record in a random access file without first
reading the preceding records.

7. Binary File
 In binary file data is stored in binary form not in
plain text.
 The records in binary files may vary in length.
 Binary files are usually smaller than text files but
user cannot view their contents with text editor.

8. Binary File
 In binary file data is stored in binary form not in
plain text.
 The records in binary files may vary in length.
 Binary files are usually smaller than text files but
user cannot view their contents with text editor.

9. Operations on File

10. File Open Mode
Input Used with sequential acess file.
Data will read from the files.
Output Used with sequential access files .
Data will be written to the file.
Append Used with a sequential access file.
Data will be written to the end of
the file.
Random This file is opened for random
access . If the file does not
exist,it is created.
Binary The file is opened in binary mode.
If the file does not exist , it is
created .

11. Opening A File
 Open statement is used to open a file.
Syntax :
Open*filename*for mode as # filenumber [len=recordlength]

12. Contd..
 When a sequential file is opened , visual basic
creates a file buffer.
 A file buffer is a small holding section of memory
that data is first written to.

13. Closing A File
 Close statement is used to close a file.
Syntax :
Close [filenumberlist]
• In syntax, Filenumberlsit is one or more file
numbers separated by commas.

14. Contd..
 The # symbol must appear with each file number.
 Example close #1,#2
 If user don’t specify any file number , visual basic
closes all the files the applications has opened.

15. Writing data to a File
 Data may be written to a file that is opened in
either output or append mode.
 The write statement is used to write a data to the
file.
Syntax
Write # filenumber, [itemlist]

16. Reading data from a file
 Data may be read from a file that already exist
and is opened in input mode.
 The input statement is used to read data from a
file.
Syntax
Input # filenumber, itemlist

17. Opening a file in append mode
 When a file is opened in append mode data is
written to the end of the file.
 If the file is already exist its contents are not
erased.
 If the file does not exist it is created.

18. Contd..
.
Syntax
Open filename for append as #1

19. Detecting the end of the file
 The EOF function detects when the end of file has been
reached.
Syntax
EOF(file number)
The function proves true if the end of file has been
reached or false if the end of file has not been reached.

20. Application on file handling

22. How to apply picture on command
button
 Select the command button.
 Draw it and then go to properties window.
 Change the style property to 1-graphical.
 Select the picture option.
 Select the picture user want to apply.

23. How to draw a shape
•Select the shape option from the toolbox.
•Then go to shape properties and select any
option.
Shape
option

24. Coding Of this Form
 Private Sub cmdappend_Click()
 Unload Me
 frmappend.Show
 End Sub
 Private Sub cmdclose_Click()
 Unload Me
 End
 End Sub

25. Contd….
 Private Sub cmdcreate_Click()
 Unload Me
 frmcreate.Show
 End Sub
 Private Sub cmdread_Click()
 Unload Me
 frmread.Show
 End Sub
 Private Sub cmdwrite_Click()
 Unload Me
 frmwrite.Show
 End Sub

27. Contd….
 Dim fname As String
 Dim productname As String
 Dim companyname As String
 Dim price As Integer
 Dim intcount As Integer
 Private Sub cmdclose_Click()
 Unload Me
 End
 End Sub

28. Contd….
 Private Sub cmdcreate_Click()
 fname = InputBox("Enter the File Name")
 Open fname For Output As #1
 For intcount = 1 To 4
 MsgBox " Enter the product details " & FormatNumber(intcount, 0)
 productname = InputBox("Enter the Product name")
 companyname = InputBox("Enter the Company name")
 price = Val(InputBox("Enter the Price"))
 Write #1, productname, companyname, price
 Next intcount
 Close #1
 End Sub

29. Control Array
 A control array is a group of controls all of the
same type.
 The control array has a name but the individual
controls in the array donot.
 To refer to a member of a control array, the
syntax is:
 ControlName(Index)[.Property]

30. How to create a control array
 Select (command button,text box ,label etc).
 Then draw it.
 Then copy it and paste it.
 It will ask do you want to create a control array
then click yes.

33. Coding
 Private Sub cmdappend_Click()
 Open "d:aman.txt" For Append As #1
 productname = "laptop"
 companyname = "samsung"
 price = 33000
 Write #1, productname, companyname, price
 Close #1
 End Sub
 Private Sub cmdclose_Click()
 Unload Me
 End
 End Sub

35. Coding
 Private Sub cmdclose_Click()
 Unload Me
 End
 End Sub
 Private Sub cmdwrite_Click()
 Open "d:aman.txt" For Output As #1
 productname = "laptop"
 companyname = "samsung"
 price = 33000
 Write #1, productname, companyname, price
 Close #1
 End Sub