A computer is an information processing machine. Information goes in
and results come out. The basic tasks of control and calculation are
carried out by a microprocessor, but when you look at a computer you
only see the peripheral devices, such as the screen, keyboard, mouse
and printer which are connected to the CPU. The equipment or hardware,
however, cannot perform any tasks without instructions in the form of
a program. This is called software. The computer also needs to store
data and software, so the hardware also includes memory chips and
other devices such as a hard disk.