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Essential Components of Computer System.

Thirunavukkarasu TC

1. Introduction to Computer Systems

A computer system is a complete, functional setup that includes hardware, software, data, and users working together to perform tasks. It’s not just the physical machine—it’s the entire ecosystem that enables computation, storage, communication, and interaction.

Key Insight: A computer cannot function meaningfully without all essential components working in harmony.

2. The Four Fundamental Components

Every computer system comprises four essential elements:

Component Role
Hardware Physical devices (e.g., keyboard, CPU, monitor)
Software Programs and instructions that tell hardware what to do
Data Raw facts and figures processed by the system
User Human operator who interacts with the system

💡 Mnemonic: H-S-D-U → Hardware, Software, Data, User

3. Hardware Components

Hardware refers to the tangible, physical parts of a computer system.

A. Input Devices

Used to enter data and instructions into the computer.

Device Function
Keyboard Text and command input
Mouse Pointing and selection
Scanner Converts physical documents to digital images
Microphone Captures audio input
Webcam Captures video
Touchscreen Combines input and output

Modern Examples: Fingerprint scanners, VR controllers, barcode readers.

B. Output Devices

Used to present processed data to the user.

Device Function
Monitor Visual display of text/graphics
Printer Produces hard copies
Speakers Audio output
Projector Large-screen display
Headphones Personal audio

Note: Some devices are I/O (Input/Output)—e.g., touchscreen, modem.

C. Central Processing Unit (CPU) – “The Brain”

The CPU executes instructions and processes data. It has three main parts:

  1. Control Unit (CU)

    • Directs the operation of the processor.
    • Fetches, decodes, and executes instructions.

  2. Arithmetic Logic Unit (ALU)

    • Performs arithmetic (addition, subtraction) and logical (AND, OR, comparisons) operations.

  3. Registers

    • Small, high-speed memory locations within the CPU for temporary data storage.

Key Terms:

  • Clock Speed: Measured in GHz; determines how fast the CPU processes instructions.
  • Cores: Modern CPUs have multiple cores for parallel processing.

D. Memory

i. Primary Memory (Main Memory)

  • Volatile (loses data when power is off).
  • Directly accessed by the CPU.
Type Full Form Purpose
RAM Random Access Memory Stores active programs and data (temporary)
ROM Read-Only Memory Stores firmware (e.g., BIOS); non-volatile

RAM Types: DRAM (Dynamic), SRAM (Static – faster, used in cache)
ROM Types: PROM, EPROM, EEPROM, Flash Memory

ii. Secondary Memory (Storage)

  • Non-volatile – retains data permanently.
  • Not directly accessed by CPU (data loaded into RAM first).
Device Characteristics
Hard Disk Drive (HDD) Magnetic storage; high capacity, slower
Solid-State Drive (SSD) Flash-based; faster, more durable
USB Flash Drive Portable, plug-and-play
Optical Discs CDs, DVDs, Blu-ray (declining use)
Cloud Storage Remote servers accessed via internet

E. Motherboard & Buses

  • Motherboard: Main circuit board connecting all hardware components (CPU, RAM, storage, etc.).
  • Buses: Communication pathways that transfer data between components.
Bus Type Function
Data Bus Transfers data between CPU and memory
Address Bus Carries memory addresses
Control Bus Sends control signals (e.g., read/write)

Expansion Slots: Allow adding cards (e.g., GPU, sound card).

4. Software Components

Software is the intangible set of instructions that control hardware.

A. System Software

Manages hardware and provides a platform for applications.

Type Examples Function
Operating System (OS) Windows, macOS, Linux, Android Manages resources, runs apps, provides UI
Utility Programs Antivirus, disk cleaners, backup tools Maintain and optimize system
Device Drivers Printer drivers, GPU drivers Enable OS to communicate with hardware
Firmware BIOS/UEFI Low-level software embedded in hardware

B. Application Software

Performs specific user tasks.

Category Examples
Productivity MS Word, Excel, Google Docs
Graphics & Media Photoshop, VLC, Audacity
Web Browsers Chrome, Firefox
Communication Zoom, WhatsApp, Email clients
Specialized MATLAB (engineering), QuickBooks (accounting)

Key Difference: System software runs in the background; application software runs in the foreground for user tasks.

5. Data

  • Raw facts (numbers, text, images, audio) that become information after processing.
  • Stored in files and databases.
  • Can be input, processed, stored, and output.

Example:

  • Data: "35, 42, 28"
  • Information: "Average temperature = 35°C"

6. Users (Human Element)

  • End Users: People who use computers for tasks (students, office workers).
  • Programmers: Write software.
  • System Administrators: Manage and maintain systems.

Without users, a computer system has no purpose.

7. Interconnection & Communication

Modern systems rely on networking:

  • Wired: Ethernet cables
  • Wireless: Wi-Fi, Bluetooth
  • Internet: Global network enabling cloud computing, email, web browsing

I/O Controllers: Chips on motherboard that manage communication between CPU and peripherals.

8. Block Diagram of a Computer System

    +------------------+
    |     USER         |
    +------------------+
            ↑↓
    +------------------+
    |   INPUT DEVICES  | ←→ Software (OS/Apps)
    +------------------+
            ↓
    +------------------+     +------------------+
    |      CPU         |←→→→|   PRIMARY MEMORY  |
    | (CU + ALU + Reg) |     |     (RAM/ROM)    |
    +------------------+     +------------------+
            ↓
    +------------------+
    | SECONDARY STORAGE|
    | (HDD, SSD, etc.) |
    +------------------+
            ↓
    +------------------+
    |  OUTPUT DEVICES  |
    +------------------+

Data Flow: Input → Processing (CPU) → Storage → Output

9. Glossary of Key Terms

  • CPU: Central Processing Unit – executes program instructions.
  • RAM: Random Access Memory – temporary working memory.
  • ROM: Read-Only Memory – permanent startup instructions.
  • Firmware: Permanent software programmed into hardware.
  • Bus: Data pathway between components.
  • Peripheral: External hardware device (e.g., printer, mouse).
  • Volatile Memory: Loses data when power is off (e.g., RAM).
  • Non-volatile Memory: Retains data without power (e.g., SSD, ROM).
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