CODEWITHSUNDEEP
excelvbabinarybinaryfilesbit
user7393973
user7393973

Reputation: 2440

Excel VBA Bit Control

In Excel VBA I'm messing around with reading and writing binary files.

I was wondering if it is possible to instead of only changing the bytes to actually work with the bits. I don't mean taking each byte and converting it to 8 bits, I mean if it is possible to create/modify/read files with bit control where it might be, for example, a file with only 4 bits, or 10, instead of always being multiple of 8.

Here's some of the code that I'm using:

Private Sub WriteFile()
  Dim path As String, num As Byte, arr(2) As Byte
  path = "test.bin"
  arr(0) = CByte(&HA1)
  arr(1) = CByte(&HC4)
  arr(2) = CByte(&HA1)
  num = FreeFile
  If Dir(path) <> "" Then Kill path
  Open path For Binary Access Write As num
  Put num, , arr
  Close num
End Sub

Upvotes: 2

Views: 598

Answers (1)

Pᴇʜ
Pᴇʜ

Reputation: 57683

Well the question is why would you do that? I think since the smallest I/O unit of a file is 1 byte (8 bits) you will always need to write 1 full byte.

The approach would be to generate a bit stream and convert that into bytes (just before writing the file).

So the approach to change one bit would be read 1 full byte change the bit in that byte and write 1 full byte back to the file.

You won't save any space on disk anyway because you always need to write 1 full sector to the disk and typically 1 sector = 512 bytes. So any file below 512 bytes will always use the full 512 bytes on the disk.

Upvotes: 4

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