Byte vs Boolean (Access 2000)

Topic

New Reply

I have just come across something interesting that I never realised, and thought that someone here may be able to spread light on it.

In the MS Access VBA help documentation, the Data Type Summary pages, states that a byte uses 1 byte of storage space (which makes sense), but a Boolean uses 2 bytes.

Now, with me, this just doesn’t seem to fit!!! A boolean is really a bit isn’t it? So why on earth would simple on, off (binary) data need to be stored as 2 bytes?

Anyone?

Reply | Quote

Replies

I have just looked in this up in several books.

3 say that a boolean takes 2 bytes, and one says it takes one bit!

They all agree that what is stored is -1 for yes and 0 for No. These are integers, so require 2 bytes.
(Is that a reasonable explanation?)

Reply | Quote

I believe it is because Access uses a signed value (0 or -1) as a boolean but will interpret any non-zero value as true. Byte datatypes are limited to unsigned values between 0 and 256.

Reply | Quote

You wrote:
>>I believe it is because Access uses a signed value (0 or -1) as a boolean but will interpret any non-zero value as true. <<

Charlotte,

I think you have to be real careful with this. For example, in de###### if you enter "? 1 = True", the response is False. However, "?CBool(1) = True" is True.

Reply | Quote

I didn’t say I used it like that, Mark. 1=True should always fail in Access because True is a constant with a value of -1. However, as you demonstrated, the CBool function evaluates the value 1 and determines that it isn’t zero so it must be True. Another way to do it is like this:

If (intNonZero) Then …

where intNonZero represents an integer variable. The parens will force an evaluation of it as a true or false expression.

Reply | Quote