Opposite of OR

[AndyGroom]

My mind has gone blank! Setting bits is easy:

a& = a& or 64

will set bit 7 of a& to 1 regardless of the other bits and regardless of whether it's already 1 or 0.

What's the opposite of that code? Ie, to set bit 7 to 0 without changing any of the other bits and regardless of whether it's already 0 or 1?

- Andy
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[petermeachem]

AND it with &HFFFFFFBF, a number with only bit 7 clear

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[Hypetia]

The standard way to set a bit is to [tt]Or[/tt] it with the required bitmask. To reset a bit, [tt]And[/tt] it with the 1's complement of the same bitmask. The 1's complement is obtained using the [tt]Not[/tt] operator.
See the following example.
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[tt]
Private Sub Form_Load()
Dim X As Byte
X = 50 '=110010b

'turn on bit #7
SetBit X, 7
MsgBox X '178=10110010b

'turn off bit #7
ResetBit X, 7
MsgBox X '50=110010b
End
End Sub

Sub SetBit(Number, Bit)
Number = Number Or (2 ^ Bit)
End Sub

Sub ResetBit(Number, Bit)
Number = Number And Not (2 ^ Bit)
End Sub[/tt]
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Note that in above functions, the Bit argument is counted from 0 instead of 1 which is more conventional. Thus LSB in a byte corresponds to Bit #0 and MSB corresponds to Bit #7.

See also thread222-1158422 in which I am doing the same thing for setting/resetting bits in a long integer.