What is carry bit?

I have confused with carry bit in many cases, still I don’t know what the real meaning is.

Ex: before this subtraction occurred TEMP = 5 & COUNT = 1


What is the result after the subtraction? What made to SET or CLEAR the carry bit?

Please explain this to me.

Thanks

The subtract instruction sets or clears the carry flag.

If the flag is set after the subtract, there was no borrow

e.g 10-4 = 6 carry flag set
also 10-10 = 0 carry flag set

If the flag is clear after the subtract there was a borrow

e.g. 4-10 = -6 Carry flag cleared

In your example

Wreg = 5, Count = 1
1-5 = -4, Carry is clear

OK thanks Geko for the reply.

Can you tell me whats my result in my example? is it -4?

Can you tell me whats my result in my example? is it -4?

Click to expand...

Yes, with carry cleared.

Ok thanks geko now I got it.