Every computer system contains hardware and software. Hardware refers to the physical components that make up a computer system.Software refers to the programs that operate the hardware.The hardware will normally consist such as the PC itself called the base unit as well as other devices connected to the base unit, such as the keyboard, mouse, printer,scanner,and so on.These devices are usually connected to the base unit by cables, or some other means.
Input devices are devices that receive information from the user, such as a keyboard, scanner, microphone or mouse.Output devices,on the other hand, are devices that send information to the user, such as a display unit, printer, or sound speakers.
Devices connected to the base unit are collectively known as peripherals.The base unit contains, amongst other things,the Central Processing Unit (CPU),which is the brain of the system,short-term memory and long-term memory in the form of hard disk drives,CDROM drives,zip drives,etc.Short-term memory comes in two main varieties on microcomputers: ROM and RAM. ROM is an acronym for Read Only Memory.
As the name suggests,this type of memory is non-volatile and permanent.This means that ROM is never erased even when the computer is shut down.Its primary purpose is to store programs that are permanently required, some of which will be described in the later sections in this chapter. RAM is an acronym for Random Access Memory and is non-permanent volatile memory.Its purpose is for storing programs and data during the running of computer programs.RAM memory is erased when the computer is shut down.