## Representation of positive,negative binary numbers.

In digital system,binary subtraction is perfrom by using 1 's and 2's complements.these forms are also used to represent negative numbers in digital systems.mostly the 2's complement method is used in computer to perform arithmatic operations with negative numbers.both 1's and 2's complement methods may appear strange when compared with direct subtraction but both these have different advantages when implemented with logic circuits for addition and subtraction.a number with sign is represented by the magnitude as well as a sign bit indicating whether number is positive or negative.in binary system,sign is represented by including an extra bit on the left along with the magnitude bits.a'o' bit represents a positive number whereas 'j'represents a negative number.computer determines the sign of the number just looking the most left digit.normally,the computer system are using an 8 bit number system.in this system most significant bit ''bit on the left side'' represents sign and remaining 7 bits represent the magnitude.