Base-8 (also called octal) number system uses eight symbols to code information. Most commonly, these symbols are, 0, 1, 2, 3, 4, 5, 6 and 7.
Base-7 (aka septenary) number system uses seven symbols to code information. Most commonly, these symbols are, 0, 1, 2, 3, 4, 5 and 6.