The five parts of every computer
Every computer, from a phone to a large server, has five kinds of unit. The input unit brings data in (keyboard, microphone, touch screen). The output unit shows results (screen, speaker, printer). The storage unit keeps data: main memory is fast but temporary, so it loses its contents when the power is off; auxiliary storage is slower but permanent. The control unit reads instructions and directs the other parts. The arithmetic-logic unit does the calculations and comparisons. The control unit and the arithmetic-logic unit together are the processor. Devices connect through interfaces, such as a port with its agreed rules, and the devices around the computer are called peripherals. Follow a small job: you type 4 and 9 (input). The numbers go into main memory. The control unit asks the arithmetic-logic unit to add them. The result 13 goes back to memory and is shown on the screen (output). If you save it, a copy goes to auxiliary storage and is still there tomorrow.
| Device or part | Unit |
|---|---|
| keyboard | input |
| screen | output |
| memory card | storage (auxiliary) |
| decides the next instruction | control unit |
| adds two numbers | arithmetic-logic unit |
| Main memory | Auxiliary storage | |
|---|---|---|
| Speed | fast | slower |
| Power off | contents lost | contents kept |
| Holds | programs and data in use | files kept for later |
Draw the five units as boxes on paper, with arrows showing how data moves when you play a short sound file: where is the file kept, where does it go to be processed, and which unit finally makes the sound?