what is bcd

BCD IS (BINARY CODED DECIMAL) here you get the binary code for any decimal number can be written in binary formate  f.e. for decimal no 1 the binary code is 0001 and for 2 it will become 0010 because it is wriiten in the formate of 8421 where the 4 digit number can have maximum of 4 one's 1111 which will be indication 15 in the decimal formate and some time to show the negative value you can write the number as 1 1111 which indicate -15 in decimal formate