Hexadecimal Number System is a base 16 number system, uses combinations of numerals 0 to 9 and alphabetic characters A to F to represent any number.
Hexadecimal numbers are represented with 16 at their base, for example 1AF16.
Definition : Octal Number System (Base 8)
Octal number system(Oct) has a base of eight and uses combinations of numerals 0 to 7 to represent any number. 128 is an example of Octal number equal to decimal 10.