AS byte can range from -127 to +127 and why its not allowing this value which i think -127
IF i'm wrong please correct me..........
The parse routine doesn't treat radix 2 different from any other radix. The value of "-127" is "-1111111" with radix 2. It doesn't understand the concept of a sign bit. Now I agree that this is awkward for binary calculations.
Adding to Henry's post: Notice that to get -128 you would have to parse the string "-10000000". Do not mistake the computer's internal twos-compliment notation with the standard mathematical binary number system notation.