The Signed Number
An 8 bit number system can be used to create 256 combinations (from 0 to 255), and the first 128 combinations (0 to 127) represent positive numbers and next 128 combinations (128 to 255) represent negative numbers.
The positive numbers are counted in a clockwise direction from 0 and the negative numbers are counted in a counter-clockwise direction.
In Decimal in order to get - 2, we subtract 2 from the number of combinations (256), which gives, 256 - 2 = 254.
In Binary all the Signed Numbers have a '1' in the Most Significant Bit (MSB) position which represents a negative number and a '0' in the Most Significant Bit (MSB) position which represents a positive number.
Also, in Binary, the 2's Complement of a number is the negative equivalent of the positive number. So, as above, +2 = 0000 0010 and the 2's Complement is 1111 1110 which represents - 2.
A 16 bit number system can be used to create 65536 combinations (from 0 to 65535), and the first 32768 combinations (0 to 32767) represent positive numbers and next 32768 combinations (32768 to 65536) represent negative numbers.
In a 16 bit number system the Signed Numbers have a '1' in the Most Significant Bit (MSB) position 1xxx xxxx xxxx xxxx which represents a negative number. A '0' in the Most Significant Bit (MSB) position 0xxx xxxx xxxx xxxx which represents a positive number.