- DEC designates "
**dec**imal," or base 10, which is what we are used to: -
`(2 x 10) + (5 x 1) = 25` - OCT designates "
**oct**al," or base 8, which works like this: -
`(3 x 8) + (1 x 1) = 25` - BIN designates "
**bin**ary," or base 2, which works like this: -
`(1 x 16) + (1 x 8) + (0 x 4) + (0 x 2) + (1 x 1) = 25` - HEX designates "
**hex**adecimal," or base 16, which works like this: -
`(1 x 16) + (9 x 1) = 25`

contributed by Steve Barber