math function to change a value 1- 8 to a bit representation

[aratti]

This snippet (not tested) should do the trick.

X VAR byte
Answer VAR byte

X = 128
Gosub Decode
' variable answer should contain your bit position
End

Decode:
Answer = 0
If X < 1 then return
Do while X <> 1
Answer = answer + 1
X = X > 1
Wend
Return

Edited:
Reading again your first post I realise you need the other way around:

X = 8
Gosub Decode
Answer will contain the requested value
End

Decode:
Answer = 0
For i = 1 to X
Answer = answer < 1
Next i
Return


Cheers

Al.