Parts of a computer system

Robert P. Webber, Longwood University

 

 

Computer systems consist of four basic parts:  Input devices, output devices, the central processing unit, and secondary storage.

 

Input devices send data to the computer from the outside world.  Common ones are the keyboard, the mouse, and the touchpad.  Some systems have microphones.  Other input devices, such as sensors, may be used on special purpose computers.

 

Output devices communicate results from the computer to the user.  Most computers have a monitor, speakers, and a printer, for instance.  Some systems may have controllers that operate motors or other mechanical devices.

 

The central processing unit (CPU) is the heart of the computer system.  Physically small, the CPU is inside the case that contains the CD drives.  On laptops, it is behind the keyboard.  All actual computing takes place in the CPU.  The CPU has several parts.  Random access memory (RAM) temporarily stores data.  Read only memory (ROM) holds data that is needed permanently by the system.  Registers and the cache are high speed memory.  Computations take place in the arithmetic logic unit (ALU).  Information is moved around on groups of wires called busses.

 

Secondary storage devices, such as disk drives, CD and DVD drives, and jump drives, hold data permanently.  Some, such as jump drives, are portable and can be used to move data between computers.  Secondary storage memory is slower for the computer to access than is RAM, but it is permanent, and it can hold far more data than RAM.