This is a number system to the base 16 and like octal code gives a shorthand version of large binary numbers. It is particularly useful in microprocessor based systems where 8 and 16 bit binary words are used. The word hexadecimal means that six alphabetical characters are used along with those representing decimal values 0 to 9. In this way letters A to F are used to represent numbers 10 to 15 with the code shown below.