[AccessD] OT: Programming Logic

> Hi All,
> 
> 	I have seen in a couple of programs that use flags to set options
> that work by giving a "binary" value, if you will, to each setting. For
> example, the first setting has the value 1, the second 2, then 4,
> 8,16,32,64,etc. Then it will add up the values of the settings that have
> been turned on. So if the 3rd, 5th, and 7th settings were turned on the
> value would be 84 (4+16+64). The totaled value generated would be unique,
> i.e. no two combinations of settings would produce the same totaled value.
> 
> 	Here is the part that I get stumped on...how would one program a
> function that would take a totaled value and "break it up" into the
> individual values that made it up? For example, if given the value 84, it
> would "break it up" as 4, 16, and 64.
> 
> Any ideas would be appreciated.
> 

To read and manipulate bits, you normally use the AND, OR and XOR bit functions.

AND returns true if both parts are true (ie bits set)

So:
 84 AND 64 =  TRUE because the "64 bit" is set in 84

In general terms:

(myNumber AND 2 ^ myBit)  returns true if the myBit  bit is set

For your example:

myNumber = 84

(myNumber AND 2 ^ myBit) 
 = false where myBit = 0 (1)
 = false where myBit = 1 (2)
 = true  where myBit = 2 (4)
 = true  where myBit = 3 (8)
 = false where myBit = 4 (16)
 = false where myBit = 5 (32)
 = true where myBit = 6 (64)
 = false where myBit = 7 (128)





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