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The reader is expected to have read the first part of this tutorial which deals
with sequential files. You can still follow this tutorial without reading Part-I,
but I recommend reading the sequential files tutorial first because I may have mentioned certain things in Part-I which also apply to Binary Files.

As far as Visual Basic 6 is concerned, there are three modes in which a file can
be accessed.

1. Text Mode (Sequential Mode)
2. Binary Mode
3. Random Access Mode

In the Text Mode, data is ALWAYS written and retrieved as CHARACTERS.
Hence, any number written in this mode will result in the ASCII Value of the
number being stored.
For Example, The Number 17 is stored as two separate characters "1" and "7".
Which means that 17 is stored as [ 49 55 ] and not as [ 17 ].

In the Binary Mode, everything is written and retrieved as a Number.
Hence, The Number 17 Will be stored as [ 17 ] in this mode and
characters will be represented by their ASCII Value as always.

One major difference between Text Files and Binary Files is that Text Files
support Sequential Reading and Writing. This means that we cannot read or write
from a particular point in a file. The only way of doing this is to read through
all the other entries until you reach the point where you want to 'actually'
start reading.

Binary Mode allows us to write and read anywhere in the file. For example we can
read data directly from the 56th Byte of the file, instead of reading all the
bytes one by one till we reach the 56th byte.

Part-I dealt with Sequential Files, and this one will teach you how to read and
write files in Binary Mode.

You will often come across the terms "Text Files", "Sequential Files",
"Sequential Mode", "Binary Mode" and "Binary Files" while reading books,
articles or even posts on the internet related to file handling and wonder what
they really mean.

A file is a set of bytes/records stored together.

Text Files are files which contain only characters in ASCII or Unicode.

Sequential Files are files opened in Sequential Mode.

Sequential Mode refers to any of the modes used for sequential file handling
which are Input, Output and Append.

Binary Mode refers to the Binary Mode [which you shall learn about as you
progress through this tutorial]

Binary Files refer to files opened in Binary Mode.

You should note that Binary Files and Sequential Files are not different kinds
of files but rather different methods of accessing a file.

Any file can be opened in both sequential and binary modes (obviously not at the
same time wink2.gif ). If it is opened in sequential mode, you will only be able to
access data in the file sequentially. If it's opened in Binary mode, you can
access any byte in the file without reading the previous bytes in the file.

example :

1. Add a Command Button with name as Command1 onto a Form
2. Private Sub Command1_Click()
3. Dim f As Long
4. f = FreeFile()
5.
6. Open "c:\test.txt" For Binary As #f
7. Close #f
8. End Sub

view plainprint?

1. 'Add a Command Button with name as Command1 onto a Form
2. Private Sub Command1_Click()
3. Dim f As Long
4. f = FreeFile()
5.
6. Open "c:\test.txt" For Binary As #f
7. Close #f
8. End Sub

As you can see, the FreeFile() function can also be used for binary files.
The Open Statement opens c:\test.txt in Binary Mode and the next statement
closes the file.

As obvious as it may sound, you need to open a file before using it and close it
when you have finished reading or writing to it. Many programmers forget to add
the Close statement which results in the File Already Open Error, and it can be
a pain to track down the exact location that caused the error when you're
dealing with many files.

You should note that this snippet does more than open and close a file.
If the test.txt file is not present in C drive, then it creates a blank file
with the same name.