Topic 2

2. Components of a Computer System

2.1 Components of A Computer

Computers are complex devices composed of many electronic parts and components. While certain components like Bluetooth or floppy disk drives may not be essential for operation today, other components are critical for a computer to function properly.

2.1.1 Computer Hardware

Hardware refers to the physical components of a computer that can be seen and touched. This includes every device and part that makes up the computer system.

The CPU

The Central Processing Unit (CPU), often referred to as the processor, is the brain of the computer. It is where most calculations occur and is the key element determining a computer's power and performance. Modern CPUs are small, square chips with metallic connectors or pins on their underside. They are inserted into a CPU socket on the motherboard, pin side down, and typically feature a heat sink and fan to dissipate heat.

The Boot Process

Upon powering on the computer, the boot process is initiated:

  1. The CPU is cleared, and the CPU register is set to F000 hex (the address of the BIOS ROM chip).

  2. The boot program in ROM BIOS is loaded into memory and performs Power-On Self-Tests (POST) to ensure all components are operational.

  3. The system checks disk drives for a boot record. When one is found, it loads the Boot Record into memory and transfers control to it.

  4. The Boot Record then loads the IO.SYS file into RAM, which includes commands to manage hardware and execute programs.

  5. The command.com file is loaded next, and finally, the autoexec.bat file runs, completing the boot process.

Intel Pentium Microprocessor Structure

An Intel Pentium Microprocessor features several components:

  • Bus Interface Unit (BUI): Links the CPU to other PC parts, retrieving instructions from RAM and sending them to the Prefetch unit.

  • Branch Predictor Unit: Interface to the "code cache," optimizing the ALUs' processing efficiency.

  • Fetch/Decode Unit:

    • Instruction Prefetch Unit: Retrieves code from the Branch Predictor.

    • Decode Unit: Translates the instruction for execution.

  • Execution Unit: Coordinates execution steps.

  • Control Unit: Assists in locating operands in DATA cache or RAM.

  • Protection Test Unit: Ensures operations are legal.

  • Registers: Hold data for processing.

  • Arithmetic Logic Unit (ALU): Processes information based on the executed instruction; the Pentium utilizes dual ALUs.

  • Floating Point Unit: Manages decimal numbers.

Motherboard

The motherboard integrates all computer components, providing connectors for the CPU, memory, input/output devices, and storage devices. Key features include:

  • Expansion Slots: For ISA and PCI devices.

  • Memory Banks: Holding SIMM and DIMM modules.

  • CPU Socket: Houses the CPU.

  • BIOS Chip: Essential for booting.

  • USB Ports: On modern motherboards.

Storage Devices

Storage devices are crucial components in a computer. They are categorized as:

  • Primary Storage: Local random-access disk storage (e.g., using RAM).

  • Secondary Storage: Includes devices like hard disks and optical disks, used for data not in current use. Secondary storage allows for greater capacity but tends to be slower and is non-volatile.

Optical Disks

Optical disks utilize lasers to read and write data. There are three main types:

  • CD-ROM: Permanent data, read-only.

  • WORM (Write Once, Read Many): Data can be written only once.

  • Erasable Optical Disks: Can be rewritten multiple times.

Optical disks are constructed from polycarbonate and include a reflective aluminum layer. They are popular for data storage and are superior in accessibility compared to older tape backups. Storage formats can vary in cost, with DVDs typically being more expensive than CDs.

Magnetic Storage

Magnetic disks, including hard disks and floppies, rely on magnetic recording and can be reused continuously. Key distinctions include:

  • Tracks: Circular rings where data bits are recorded.

  • Sectors: Smallest storage unit, typically 512 bytes.

  • Clusters: Groups of sectors represented during read/write operations.

RAID (Redundant Array of Inexpensive Disks)

RAID technology involves multiple hard drives in an array, providing improved performance and redundancy. Common RAID levels include multi-drive configurations with both data striping (RAID 0) and mirroring (RAID 1).

2.2 Computer Software

2.2.1 Operating System

The operating system (OS) is a critical program that manages hardware and software interactions. Important roles include:

  • Memory management

  • Input/Output management

  • File management

  • Authorization management and security

  • Execution management for applications

Variants of the OS support various functionalities including multiuser access and real-time responses.

2.2.2 Software Utilities

Utility programs maintain computer health and may include:

  • File management tools

  • Disk management applications

  • Memory management software

  • Backup and data recovery programs

  • Security applications to protect against malware threats

2.3 Computer Layers

Computers are designed in layers, each representing distinct operations and components. Layers range from application interfaces to digital logic circuits.

2.4 Von Neumann Model

The Von Neumann architecture integrates where instructions and data reside in a shared memory arrangement. The model emphasizes CPU functionality, encompassing:

  • Control Unit and Arithmetic/Logic Unit interactions

  • Instruction set architecture and processing optimization via caches

2.5 Access Methods

An access method pertains to how data moves between computer systems and external devices, determining storage retrieval techniques.

2.6 ROM-BIOS

ROM-BIOS is fundamental for controlling the computer's basic functions and ensuring a successful boot sequence. Flash BIOS technology has become prevalent, enhancing BIOS functionality.

Revision Questions

  1. Describe the broad categories of computer components.

  2. Explain the components of the CPU.

  3. What are the levels that constitute a computer system?

  4. Discuss how data is accessed in a computer system.

  5. Illustrate the Von Neumann computer architecture.


Malware, short for malicious software, refers to any software intentionally designed to cause damage to a computer, server, client, or computer network. It encompasses various types, including viruses, worms, trojan horses, ransomware, spyware, adware, and more. Each type has its own method of operation and intended impact:

  • Viruses: Attach themselves to legitimate programs and spread when the infected program is executed.

  • Worms: Replicate themselves to spread to other computers without requiring a host program.

  • Trojan Horses: Pretend to be legitimate software but carry out malicious actions under the surface once installed.

  • Ransomware: Encrypts a user's files and demands payment for the decryption key.

  • Spyware: Secretly monitors user activity to gather personal information.

  • Adware: Automatically delivers advertisements, often unwanted and intrusive.

Preventive measures against malware include the use of antivirus software, firewalls, and practices like not clicking on suspicious links or downloading unknown attachments.

Here are some revision questions based on the notes:

  1. Describe the broad categories of computer components.

  2. Explain the components of the CPU and their functions.

  3. What are the main layers that constitute a computer system, and what happens at each layer?

  4. Discuss how data is accessed in a computer system, including various methods.

  5. Illustrate the Von Neumann computer architecture and its key components.

  6. What is the role of the operating system in managing hardware and software interactions?

  7. Define malware and list the different types along with their characteristics.