Lesson 2 –Fundamentals of a computer system
What is a Computer?
A computer is an electronic device that collects data, processes it according to instructions, and
produces output. Computers are essential in daily life due to their speed, accuracy, efficiency,
versatility, and ability to store and retrieve large amounts of data.
Classification of Computers
1. According to Physical Size:
o Super Computers: Very powerful, large, expensive; used for scientific,
engineering, and military tasks.
o Mainframe Computers: Powerful but smaller than supercomputers; support
multiple users; used in large businesses.
o Mini Computers: Medium size; used by fewer users; common in banks and
medium-scale institutions.
o Micro Computers: Small, personal use; examples include PCs, laptops, and
smartphones.
2. According to Technology:
o Analog Computers: Use analog signals (e.g., speedometers, sensors).
o Digital Computers: Use digital signals; common in daily life (e.g., PCs).
o Hybrid Computers: Combine analog and digital features (e.g., ECG machines).
Function of a Computer System
The main functions of a computer system are to input, process, store data, and produce output.
Input devices feed data to Primary Memory.
CPU processes data and sends results to output devices.
Secondary Storage saves data for future use.
Control Unit (CU) manages all operations by sending control signals.
Basic Physical Components of a Computer System
1. Input Devices:
o Keyboard: Common device for typing and commands.
o Mouse: Pointing device with left/right buttons and a wheel.
o Touch Screen: Acts as input/output by touch.
o Joy Stick: Moves cursor, mainly for gaming.
o Light Pen: Used for selecting/drawing on screens.
2. Imaging and Video Input Devices:
o Digital Camera: Captures photos/videos.
o Webcam: Captures live video, often for internet use.
o CCTV: Feeds surveillance footage to computers.
o Flatbed Scanner: Scans documents/photos.
o Bar Code Reader: Reads barcodes into computers.
o MICR: Reads information from cheques.
o OCR: Captures editable text from documents.
o OMR: Reads marked answers (like MCQ answer sheets).
o ATM: Reads card information and connects with bank computers.
o Microphone: Inputs sound to a computer.
Output Devices of a Computer System
A computer produces output in three main forms:
Soft Copy
Hard Copy
Sound
(i) Soft Copy
Displayed electronically, not permanent.
Monitor/Screen (VDU):
o CRT: Bulky and uses more electricity.
o LCD: Flat screen, uses liquid crystals, consumes less electricity.
o LED: Uses light-emitting diodes, bright and energy-efficient.
Multimedia Projector: Projects screen output onto a large surface for group viewing.
(ii) Hard Copy
Printed, tangible output.
Printers:
o Impact Printers (noisy, cheaper)
Dot Matrix Printer: Prints by striking dots.
Line Printer: Prints entire lines at once, very fast.
o Non-Impact Printers (quiet, better quality)
Laser Printer: Uses toner powder.
Ink Jet/Bubble Printer: Sprays liquid ink.
Thermal Printer: Uses heat to print, common in receipts.
Plotter:
o Draws large designs (used in architecture, planning).
(iii) Sound
Speakers and Headphones: Provide sound output for personal or public use.
Central Processing Unit (CPU)
Main component and brain of the computer.
Manages operating system and software.
Components:
1. Arithmetic and Logic Unit (ALU): Performs calculations and logic operations.
2. Control Unit (CU): Controls devices and system operations.
3. Memory Registers: Temporarily store data for ALU processing.
Computer Speed:
Measured in Hertz (Hz), Megahertz (MHz), and Gigahertz (GHz).
Computer Memory
1. Primary Memory (Direct access by CPU):
RAM (Random Access Memory): Volatile, read/write memory.
ROM (Read Only Memory): Non-volatile, stores BIOS.
Cache Memory: Fast, small memory between CPU and RAM.
2. Secondary Memory (Permanent storage):
Magnetic Media: Hard disk, Magnetic tape.
Optical Media: CD, DVD, Blu-ray.
Solid State Devices: USB flash drive, Memory card (e.g., SD card).
Computer Ports
Interfaces connecting devices to computers. Connected to the motherboard.
Types of Ports:
1. PS/2 Port: Connects keyboard and mouse (color-coded).
2. Parallel Port: Connects printers (25 holes).
3. HDMI Port: Connects monitors, TVs, projectors.
4. RJ 45 Port: Connects network cables.
5. Audio Ports: Connect microphones, speakers, headphones.
6. USB Port: Connects various input/output devices.
7. Video Port (VGA): Connects monitor/projector (15 holes).
8. Serial Port: Older connection for modems (replaced by USB).
