A86: Negative numbers, sign bits, and the sign flag.


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A86: Negative numbers, sign bits, and the sign flag.




	I have read that a negative byte is represented by counting down from 
255.  So -1 would be 254, -2 would be 253, etc.  But how do you know if 
%11111101 represents 253 or -2?  I have also read that bit 7 of a byte is 
called the sign bit and can be used to determine if a number is positive or 
negative, but this does not make sense to me since %11111110 is 254 which is 
a positive number even though the sign bit is set. (Unless you interpret it 
as -1 which goes back to my first question.)  And also, when and how is the 
sign flag affected and how can you check it?  Thanks for your help.