Computer System and Its Components
Computer System
A computer system is a set of integrated hardware and software components that work together to input, process, store, and output data and information.
A computer system is built around a processing device and consists of several interconnected components.
The five major hardware components of a computer system are:
- Input Devices
- Processing Unit
- Storage Devices
- Output Devices
- Communication Devices
This chapter mainly discusses the input unit, output unit, and processing unit.
Components of a Computer System
1. Input Unit
The input unit is responsible for entering data and instructions into a computer.
A computer performs a task only after receiving appropriate data and commands.
Input may include:
- Numbers
- Text
- Images
- Audio
- Video
- Instructions
The entered data is converted into a form that the computer can process.
Common input devices include:
- Keyboard
- Mouse
- Touchpad
- Touchscreen
- Trackball
- Graphics Tablet
- Scanner
- Webcam
- Microphone
- Barcode Reader
- Biometric Scanner
- Gamepad / Joystick
- Motion Sensor
- Light Pen
- Gesture Recognition Device
- Remote Control
Keyboard
A keyboard is an input device used to enter text, numbers, symbols, and commands into a computer.
It is one of the most commonly used input devices.
A standard keyboard contains:
- Alphabet keys
- Number keys
- Function keys
- Special-character keys
- Navigation keys
- Control keys
Mouse
A mouse is a pointing input device used to control the movement of a pointer or cursor on a computer screen.
It allows users to:
- Point
- Click
- Select
- Drag
- Scroll
- Open files and applications
A mouse is commonly used with a Graphical User Interface (GUI).
Touchpad
A touchpad is a flat, touch-sensitive pointing device commonly found on laptops.
Users move their fingers across its surface to control the cursor.
A touchpad can perform actions such as:
- Moving the pointer
- Clicking
- Scrolling
- Dragging
- Zooming
Touchscreen
A touchscreen is a display that can detect touch input from a user.
Users can interact directly with the screen by touching icons, buttons, menus, or other objects.
Because it displays information and accepts touch commands, a touchscreen functions as both an input and output device.
Trackball
A trackball is a pointing device containing a ball that can be rotated by the user.
Sensors detect the movement of the ball and move the cursor accordingly.
Unlike a mouse, the entire device usually remains stationary while the ball is rotated.
Graphics Tablet
A graphics tablet, also known as a drawing tablet, is an input device that allows users to draw or write digitally using a stylus.
It is commonly used by:
- Graphic designers
- Artists
- Architects
- Engineers
- Animators
Scanner
A scanner is an input device used to convert printed documents, photographs, and images into digital form.
The scanned content can then be:
- Viewed
- Edited
- Stored
- Shared
on a computer.
Webcam
A webcam is a digital camera used to capture images and video for a computer.
It is commonly used for:
- Video conferencing
- Online classes
- Live streaming
- Online meetings
- Video recording
Microphone
A microphone is an input device used to capture sound.
It converts sound waves into signals that can be processed, recorded, transmitted, or stored by a computer.
Microphones are commonly used for:
- Voice recording
- Online meetings
- Voice commands
- Video calls
- Audio production
Barcode Reader
A barcode reader is an input device used to scan and decode information stored in a barcode.
It is commonly used in:
- Shops
- Supermarkets
- Warehouses
- Libraries
- Inventory systems
Biometric Scanner
A biometric scanner is an input device used to capture unique physical or biological characteristics of a person for identification or verification.
Examples include:
- Fingerprint scanners
- Face recognition systems
- Iris scanners
The captured biometric information can be compared with stored records to approve or deny access.
Gamepad and Joystick
A gamepad or joystick is an input device mainly used for controlling computer and video games.
These devices may contain:
- Buttons
- Triggers
- Directional controls
- Analog sticks
They allow users to control characters, vehicles, and other objects in virtual environments.
Motion Sensor
A motion sensor is a device that detects movement within a particular area.
Motion sensors may use technologies such as:
- Infrared
- Ultrasonic waves
- Microwaves
They are commonly used in:
- Security systems
- Automatic lighting
- Home automation
- Alarm systems
- Automatic cameras
Light Pen
A light pen is a pen-shaped pointing input device that was used mainly with older display technologies.
It allowed users to interact directly with objects displayed on compatible computer screens.
Light pens were used for tasks such as:
- Selecting screen objects
- Drawing
- Entering information
Gesture Recognition Device
A gesture recognition device detects and interprets human movements or gestures.
It may use:
- Cameras
- Depth sensors
- Motion sensors
- Accelerometers
Gesture recognition technology is used in:
- Gaming
- Smartphones
- Virtual Reality
- Smart TVs
- Interactive systems
Remote Control
A remote control is a handheld input device used to operate electronic equipment from a distance.
It commonly uses:
- Infrared (IR)
- Radio Frequency (RF)
signals.
Remote controls are used with devices such as:
- Televisions
- Multimedia systems
- Air conditioners
- Smart devices
2. Output Unit
The output unit presents the processed information produced by a computer to the user.
After a computer processes input data, the result is called output.
Output can be presented as:
- Text
- Images
- Audio
- Video
- Printed documents
Output can broadly be classified into:
- Softcopy Output
- Hardcopy Output
Softcopy Output
A softcopy is information presented in electronic or digital form.
It is not permanently printed on physical material.
Softcopy output can be viewed, heard, or stored electronically.
Examples include output displayed through:
- Monitor
- Projector
- Smartphone or Tablet Screen
- E-book Reader
- Digital Signage Display
- Digital Photo Frame
- Speakers or Headphones
Monitor / Display
A monitor is the most common visual output device.
It displays:
- Text
- Images
- Graphics
- Videos
- Software interfaces
on a screen.
Projector
A projector is an output device that displays computer-generated images or videos on a large screen, wall, or other surface.
It is commonly used in:
- Classrooms
- Meetings
- Conferences
- Presentations
- Cinema and entertainment
E-book Reader
An e-book reader is an electronic device designed mainly for displaying and reading digital books and documents.
Smartphone and Tablet Display
Smartphones and tablets contain screens that display various forms of digital information, including:
- Text
- Images
- Videos
- Applications
Because these devices also accept touch input, they are multifunctional devices.
Digital Signage Display
A digital signage display is a screen used to display digital content in public or commercial places.
It may display:
- Advertisements
- Announcements
- Information
- Multimedia content
Digital Photo Frame
A digital photo frame is an electronic display designed to show digital photographs, usually as a slideshow.
Hardcopy Output
A hardcopy is a physical and tangible form of computer output.
It can be physically handled and does not require a screen for viewing.
Common hardcopy output devices include:
- Printer
- Plotter
- 3D Printer
- Thermal Printer
- Label Printer
Printer
A printer is an output device that produces text and graphics on paper or another physical medium.
Common types of printers include:
- Inkjet Printer
- Laser Printer
- Dot Matrix Printer
Plotter
A plotter is an output device used to produce large and precise drawings.
It is commonly used for:
- Engineering drawings
- Architectural plans
- Maps
- Technical designs
Photocopier
A photocopier is primarily used to make duplicate copies of physical documents.
Modern multifunction photocopiers may also include scanning, printing, and network functions.
3D Printer
A 3D printer produces three-dimensional physical objects from digital models.
Objects are generally created by adding material layer by layer.
3D printers are commonly used in:
- Prototyping
- Engineering
- Manufacturing
- Education
- Product development
Fax Machine
A fax machine is used to send and receive copies of documents over a communication network.
Traditional fax systems scan a document, transmit its information, and reproduce the document at the receiving side.
Thermal Printer
A thermal printer uses heat to produce printed output.
It is commonly used for:
- Receipts
- Point-of-sale systems
- Tickets
- Labels
Label Printer
A label printer is a specialized printer designed to produce labels.
It is commonly used for:
- Shipping labels
- Barcode labels
- Product labels
- Address labels
Impact Printer and Non-Impact Printer
Printers can also be classified according to their printing mechanism into:
- Impact Printers
- Non-Impact Printers
Impact Printer
An impact printer produces output by physically striking an inked ribbon against paper.
Examples
- Dot Matrix Printer
- Daisy Wheel Printer
Non-Impact Printer
A non-impact printer produces output without striking an inked ribbon against the paper.
Examples
- Laser Printer
- Inkjet Printer
Difference Between Impact and Non-Impact Printer
| Impact Printer | Non-Impact Printer |
|---|---|
| Prints by physically striking a ribbon against paper. | Prints without a striking mechanism. |
| Produces comparatively more noise. | Operates comparatively quietly. |
| Printing quality is generally lower. | Printing quality is generally better. |
| Commonly uses an inked ribbon. | May use ink, toner, or thermal technology. |
| Generally slower for high-quality printing. | Modern models are generally faster and more suitable for high-quality output. |
| Useful where multipart forms are required. | Commonly used for normal office and home printing. |
| Examples: Dot Matrix, Daisy Wheel. | Examples: Laser, Inkjet. |
3. Processing Unit
After receiving data and instructions from the input unit, the computer processes them according to the given instructions.
The Central Processing Unit (CPU) performs the major processing operations of a computer.
Important components associated with processing include:
- Control Unit
- Arithmetic and Logic Unit
- Registers
- Memory used during processing
Memory Unit
The memory unit stores data, instructions, and intermediate results required during processing.
Data entered through input devices may be temporarily stored in memory before and during processing.
Memory allows the CPU to access the data and instructions required to perform operations.
Control Unit
The Control Unit (CU) manages and coordinates the activities of the computer system.
Its major functions include:
- Fetching instructions
- Decoding instructions
- Controlling their execution
- Coordinating the CPU and other components
- Directing the flow of data
The Control Unit helps ensure that instructions are performed in the correct sequence.
Arithmetic and Logic Unit
The Arithmetic and Logic Unit (ALU) is a part of the CPU that performs arithmetic and logical operations.
Arithmetic Operations
Examples include:
- Addition
- Subtraction
- Multiplication
- Division
Logical Operations
Examples include:
- Comparison
- AND
- OR
- NOT
- XOR
The ALU plays a major role in calculations and decision-making operations performed by the processor.
Microprocessor
A microprocessor is an Integrated Circuit (IC) that performs CPU-related processing functions.
A microprocessor contains or works closely with important components such as:
- Arithmetic and Logic Unit
- Control Unit
- Registers
- Clock
- Cache Memory
Components of a Microprocessor
1. Arithmetic Logic Unit (ALU)
The ALU performs mathematical and logical operations.
Arithmetic operations include:
- Addition
- Subtraction
- Multiplication
- Division
Logical operations include:
- AND
- OR
- NOT
- XOR
- Comparison operations
2. Control Unit (CU)
The Control Unit coordinates the execution of instructions.
It performs operations such as:
- Fetching instructions from memory
- Decoding instructions
- Controlling their execution
- Sending control signals to other CPU components
3. Registers
Registers are very small and high-speed storage locations associated with the CPU.
They temporarily store:
- Data
- Instructions
- Memory addresses
- Intermediate results
during processing.
Important types of registers include:
- Program Counter
- Instruction Register
- Accumulator
- Memory Address Register
- Memory Data Register
- General-Purpose Registers
Program Counter (PC)
The Program Counter (PC) stores the memory address of the next instruction to be fetched and executed.
Instruction Register (IR)
The Instruction Register (IR) holds the current instruction being decoded or executed.
Accumulator (ACC)
The Accumulator (ACC) stores intermediate or final results produced by arithmetic and logical operations.
Memory Address Register (MAR)
The Memory Address Register (MAR) stores the address of a memory location that the processor needs to access.
Memory Data Register (MDR)
The Memory Data Register (MDR) temporarily holds data being transferred between the processor and memory.
General-Purpose Registers (GPRs)
General-Purpose Registers are used for various temporary storage purposes during program execution.
They may store:
- Operands
- Addresses
- Intermediate results
- Temporary values
Clock
The clock provides timing signals used to synchronize processor operations.
It generates regular electrical pulses known as clock cycles.
Clock frequency is measured in Hertz (Hz) and commonly expressed using units such as:
- MHz — Megahertz
- GHz — Gigahertz
Cache Memory
Cache memory is a small and very fast memory located in or close to the CPU.
It temporarily stores frequently or recently accessed data and instructions.
Cache memory helps improve computer performance by reducing the time required to obtain information from slower main memory.
Word Length
Word length refers to the number of bits a CPU can process as a unit in a particular architectural context.
Examples include:
- 8-bit
- 16-bit
- 32-bit
- 64-bit
Word length affects capabilities such as:
- Data processing
- Register size
- Memory addressing
- Overall processor architecture
Quick Revision
Computer System
A computer system consists of integrated components that work together to:
Input → Process → Store → Output Data
Major Hardware Components
- Input Unit
- Processing Unit
- Storage Unit
- Output Unit
- Communication Devices
Common Input Devices
- Keyboard
- Mouse
- Touchpad
- Touchscreen
- Trackball
- Graphics Tablet
- Scanner
- Webcam
- Microphone
- Barcode Reader
- Biometric Scanner
- Joystick / Gamepad
- Motion Sensor
- Light Pen
- Gesture Recognition Device
- Remote Control
Output
Output can be classified as:
Softcopy
Electronic or digital output.
Examples:
- Monitor
- Projector
- Digital display
Hardcopy
Physical output.
Examples:
- Printer
- Plotter
- 3D Printer
Printers
Printers may be:
Impact Printers
Printing involves physical striking.
Examples:
- Dot Matrix
- Daisy Wheel
Non-Impact Printers
Printing takes place without striking the paper.
Examples:
- Laser
- Inkjet
Processing Unit
Important processing components include:
- Control Unit
- Arithmetic and Logic Unit
- Registers
- Memory used during processing
Microprocessor Components
- ALU
- Control Unit
- Registers
- Clock
- Cache Memory
Important Registers
- PC — Program Counter
- IR — Instruction Register
- ACC — Accumulator
- MAR — Memory Address Register
- MDR — Memory Data Register
- GPR — General-Purpose Register
Important Exam Points
- A computer system consists of several integrated components.
- Input devices are used to enter data and instructions.
- A keyboard is mainly used for entering text and commands.
- A mouse, touchpad, and trackball are pointing devices.
- A touchscreen acts as both an input and output device.
- A scanner converts physical documents or images into digital form.
- A biometric scanner is used for identity verification.
- Output is the result produced after processing.
- Softcopy output is electronic.
- Hardcopy output is physical.
- Impact printers use a striking mechanism.
- Non-impact printers do not use a striking mechanism for printing.
- The CPU performs the major processing operations.
- The Control Unit manages and coordinates processing activities.
- The ALU performs arithmetic and logical operations.
- Registers provide high-speed temporary storage.
- The Program Counter stores the address of the next instruction.
- The Instruction Register holds the current instruction.
- The Accumulator stores results of arithmetic and logical operations.
- MAR stores a memory address.
- MDR temporarily stores data being transferred to or from memory.
- The processor clock synchronizes operations.
- Cache memory helps provide faster access to frequently used data and instructions.
- Word length describes the number of bits handled as a unit by a processor architecture.
Discussion
Share a helpful question, idea, or explanation with other students.