bc is an arbitrary precision calculator language
type "bc" in command line and press Enter, then you can use it to do some caculation.
type 1 + 1 and press Enter then you will get 2 on the screen.
type 1 - 1 and press Enter then you will get 0 on the screen.
type 2 * 3 and press Enter then you will get 6 on the screen.
type 2 / 3 and press Enter then you will get 0 on the screen.
type 2 % 3 and press Enter then you will get 2 on the screen.
type "quit"