ZIMSEC O Level · Computer Science · Form 1, Form 2
A computer is an electronic device that accepts data (input), processes it, stores it and produces information (output).
Hardware
- Input devices: keyboard, mouse, touch screen, scanner, microphone, barcode reader, webcam, sensors.
- Output devices: monitor, printer (laser, inkjet), speakers, projector, actuators.
- Processor (CPU): the control unit directs operations; the arithmetic logic unit (ALU) performs calculations and comparisons; registers hold data being processed. Speed is measured in gigahertz (GHz).
- Memory: RAM is volatile (lost when power is off) and holds programs in use; ROM is non-volatile and holds start-up instructions.
Storage
- Magnetic: hard disk drives – large and cheap.
- Solid state: SSDs and flash drives – fast, no moving parts.
- Optical: CDs, DVDs.
- Cloud storage: files kept on remote servers over the internet.
Software
- System software: operating systems (Windows, Android, Linux) manage hardware, files, memory and security; utilities (antivirus, backup, compression).
- Application software: word processors, spreadsheets, databases, browsers, games.
Exam tip: Volatile = loses data without power. RAM is volatile; ROM is not.
Check yourself
- State the function of the ALU.
- Give one difference between RAM and ROM.
- Name two functions of an operating system.
Show answers
- Performs arithmetic calculations and logical comparisons.
- RAM is volatile and can be written to; ROM is non-volatile and read-only.
- Any two: manages memory, files, hardware/devices, security, user interface, runs programs.
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