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Testing variable bit

I'm having some problems testing bit 0 of a variable to see if it's a 1. Here's the snippet of the code:

if ((bWork && 0x01)==1)
       bTemp = bTemp|0x01;
else
       bTemp = bTemp & 0xFE;

The problem is that whenever bWork > 0 (such as when bWork = 0xFC), it drops into the if statement even though it should be zero and drop into the else statement.
I probably have a syntax error but don't see it.

0 Jon Ward over 22 years ago
You are using a logical AND instead of a bitwise AND. The following code does what you want:

if ((bWork & 0x01)==1) bTemp = bTemp|0x01; else bTemp = bTemp & 0xFE;

Note that this if...then stuff could all be handled with bitwise logic using the following statement:

bTemp ^= (bWork & 0x01);

This generates about half the code of the if...then.

Jon
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0 Drew Davis over 22 years ago
&& is logical and. & is bitwise and. The given snippet will take the if path whenever bWork is "true" (non-zero). (The other operand, "0x01", is always true, so it only depends on bWork.) You probably want:

if ((bWork & 0x01) == 1)

to test just bit 1 of bWork.
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0 Mike Collins over 22 years ago

Thanks. And thanks for the tip on the if .. then statement Jon. You learn something new everyday.
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0 Andrew Neil over 22 years ago in reply to Mike Collins

"You learn something new everyday."

Looking at your original post, you probably also want to check out the |= and &= operators in your 'C' text book (and += etc).
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