Computer Hardware and Software Notes

Concepts of Computer Systems and Data Representation

• Computer System Definition

  • An interrelated set of components, including both hardware and software, that work together to convert raw data into usable information.

• Fundamental Components

  • Hardware: The physical, tangible components of a computing system (input devices, central processing unit, memory, output devices, and storage devices).
  • Software: Computer programs, sets of instructions, and code routines that execute on the hardware layer to perform operational tasks.

• Electronic Data Representation

  • Computers utilize the Binary System as their fundamental data-representation method.
  • Uses two distinct states represented by digits $0$ and $1$, corresponding to the off/on states of electrical circuits or optical light pulses.
  • Data is stored, processed, and transmitted electronically via binary code.

• Units of Data Measurement
  • Bit: A single binary digit representing either a $0$ (off state) or a $1$ (on state). It is the smallest unit of data in computing.
  • Nibble: Exactly half of a byte, consisting of $4\text{ bits}$.
  • Byte: Composed of $8\text{ bits}$. It serves as the basic practical unit of data and represents the storage space required to hold a single alphanumeric character.
  • Kilobyte (KB): Approximately $1000\text{ bytes}$ (or precisely $1024\text{ bytes}$, where $1024\text{ Bytes} = 1\text{ Kilobyte}$), equivalent to 1000 characters.
  • Megabyte (MB): Approximately $1000\text{ KB}$ (or precisely $1024\text{ KB} = 1\text{ Megabyte}$), representing approximately one million characters.
  • Gigabyte (GB): Approximately $1000\text{ MB}$ (or precisely $1024\text{ MB} = 1\text{ Gigabyte}$), representing approximately one billion characters.
  • Terabyte (TB): Approximately $1000\text{ GB}$ (or precisely $1024\text{ GB} = 1\text{ Terabyte}$).
  • Petabyte (PB): Exactly $1024\text{ TB} = 1\text{ Petabyte}$.
  • Exabyte (EB): Exactly $1024\text{ PB} = 1\text{ Exabyte}$.

Internal Architecture and Components of the System Unit

• System Unit Form Factors

  • System Unit: The main enclosure containing the electronic computer components used for data processing.
  • Desktop / Tower PCs: System units housed in standalone chassis where the monitor is completely separate.
  • Laptops: Integrated system units where the display monitor is attached to the base using a hinged clamshell design.
  • Tablets: Flat system units that integrate primary user interaction via a touch-screen interface.
  • Smartphones: Compact, handheld system units containing embedded computing architecture.

• Motherboard Architecture

  • The primary printed circuit board (PCB) inside the system unit to which all internal and external computer components connect.
  • Directly connects core components like the CPU and main memory.
  • Input devices such as keyboards and mice connect either directly to integrated ports on the motherboard or via peripheral interface connectors.
  • Expansion cards and external hardware attach through expansion slots and input/output ports.

• Key Internal Hardware Components
  • Power Supply: Converts alternating current (AC) electrical power from external outlets into regulated direct current (DC) power for internal system components.
  • Microprocessor / CPU Chip: Integrated circuit chip mounted on the motherboard executing main processing functions.
  • Cooling Fans & Extra Case Fan: Heat dissipation devices mounted on top of processing units and on system enclosure walls to prevent thermal failure.
  • Motherboard: Mounted behind internal wiring and ribbon cables, acting as the structural communication backbone.
  • Ribbon Cables & Power Cords: Internal wiring buses used for high-speed data transfer between controllers and drives, alongside internal DC power distribution wires.
  • Expansion Cards: Modular circuit boards inserted into motherboard slots to add specialized capabilities, including Video Cards, Modem Cards, and Sound Cards.
  • Optical Drives: Internal disk hardware such as CD/DVD drives mounted in front-facing drive bays.
  • Hard Disk Drive: High-capacity secondary storage unit installed inside the internal storage chassis.

Central Processing Unit Architecture and Processing Dynamics

• Role and Structure of the CPU

  • The Central Processing Unit (CPU) functions as the structural "brain" of the computer system, following software program instructions to manipulate data into actionable information.
  • Connected internally via high-speed electronic conduction pathways called a bus, which transports electrical signals between components and system memory.

• Core CPU Subsystems

  • Control Unit (CU):
  • Stores the hardwired instruction set built directly into the silicon physical circuitry.
  • Retrieves individual program instructions sequentially from main memory.
  • Decodes and interprets instructions into lower-level internal machine commands.
  • Passes arithmetic or logic execution routines directly to the Arithmetic/Logic Unit (ALU).
  • Manages overall system hardware components, coordinates system activities, and directs the flow of data within the system unit.
  • Arithmetic/Logic Unit (ALU):
  • Serves as the internal calculator responsible for instruction execution.
  • Arithmetic Operations: Performs fundamental mathematical computations including addition ($+$), subtraction ($-$), multiplication, and division.
  • Logical Operations: Performs data value evaluations and comparison tests to determine equality or relational thresholds: equal to ($=$), greater than ($>$), greater than or equal to ($\ge$), less than ($<$), less than or equal to ($\le$), or not equal to ($\ eq$).
  • Registers: Ultra-fast, localized internal CPU storage regions designed for temporary holding of data elements, current instructions, and internal execution addresses.

• Processing Speeds and System Clock

  • Driven by an internal quartz oscillator called the System Clock, which emits pulses at fixed intervals to synchronize all processing routines and operations.
  • Megahertz (MHz): Measurement used in older processors; $1\\text{ MHz} = 1\\text{ million clock cycles per second}$.
  • Gigahertz (GHz): Standard measurement for modern processors; $1\\text{ GHz} = 1\\text{ billion clock cycles per second}$.
  • Performance trade-offs: Operating a CPU at higher clock speeds exponentially increases electrical power consumption and elevates operational heat production.

• Multicore Architecture

  • An integrated chip containing two or more completely independent, actual hardware processing cores on a single physical package.
  • Enables real-time simultaneous processing of independent execution threads (multitasking).
  • Delivers enhanced computational performance while minimizing total power draw and thermal output.

• The Machine Cycle
  • The standard sequential operational loop executed by the control unit for every software instruction:
  1. Fetch: Retrieve an instruction from Main Memory.
  2. Decode: Translate the retrieved instruction into specific computer operational commands.
  3. Execute: Process the decoded commands using internal processing circuitry (ALU or CU).
  4. Store: Write the computation results back into computer memory.

Hardware Categories: Input, Output, and Storage Media

• Input Devices

  • Specialized hardware peripherals used to feed raw data, commands, control signals, or user instructions into a computer system.
  • Keyboard and Mouse: Standard character input and desktop point-and-click pointer controllers.
  • Gaming Controllers: Game pads and Joysticks designed for multi-axis directional input in real-time environments.
  • Scanning Devices: Flatbed Scanners (document digitization) and Handheld Barcode Scanners (reading optical linear barcode lines).
  • Audio/Visual Input: Microphones (analog audio stream capture) and WebCams (live optical video signal capture).
  • Biometric & Security Input: Iris Scanners (scanning ocular patterns), Fingerprint Scanners (biometric ridge reading), Hand Scanners (palm geometry authentication), and Touch-screen digitizers.
  • Transaction & Financial Input: Magnetic Strip Card Readers (reading encoded magnetic credit/debit strips) and Signature Scanners (e.g., Wacom digital signature capture pads).

• Primary Storage (Main Memory)

  • High-speed storage layer directly accessible by the CPU; stores active software programs and operational data currently undergoing active execution.
  • Volatile Memory (RAM - Random Access Memory): Fast workspace storage holding pending data and active process instructions. All contents are lost instantly when electrical power to the computer system is switched off.
  • Non-Volatile Memory (ROM - Read-Only Memory): Firmware storage containing permanent, unerasable instructions (such as boot code). Retains contents intact without requiring continuous electrical power.

• Secondary Storage Architecture

  • Non-volatile, high-capacity storage layer detached from the CPU's direct execution space; designed for long-term data retention.
  • Characteristics: Inexpensive per gigabyte, non-volatile, large capacity, but operates slower than primary RAM memory.
  • Primary selection parameters for secondary storage systems are Storage Capacity and Read/Write Access Speed.

• Secondary Storage Media Implementations

  • Optical Disks: Data read and written using focused laser light beams rather than physical mechanical heads.
  • CD-ROM / DVD-ROM: Compact Disk / Digital Versatile Disk Read-Only Memory containing permanently prerecorded factory data.
  • CD-R / DVD-R: Recordable optical disks allowing data to be burned a single time.
  • CD-RW / DVD-RW / DVD-RAM / DVD+RW: Erasable optical media capable of repeated record and erase cycles.
  • DVD Capacity Parameters: Single-sided DVDs store $4.7\\text{ GB}$ of data; double-sided DVDs store up to $9.4\\text{ GB}$.
  • Blu-ray: High-capacity optical disk standard using blue-violet lasers to record, rewrite, and play back high-definition (HD) digital video and store large data files.
  • Flash Drives: Solid-state, highly portable storage devices using USB interfaces; electronically erasable and rewritable.
  • Magnetic Tapes: Ribbon-based magnetic storage media used primarily for high-capacity corporate enterprise archiving, sequential logging, and mass system backups.

• Output Devices
  • Peripherals designed to convert computer processing results from digital bit sequences into human-understandable visual, printed, or auditory forms.
  • Visual Display Units (Monitors):
  • CRT (Cathode Ray Tube): Older, bulky electron gun displays.
  • LCD (Liquid Crystal Display): Modern flat-panel displays utilizing polarization layers and liquid crystals.
  • Hard-Copy Printers:
  • Dot-Matrix Printers: Impact printers striking ink ribbons against continuous paper.
  • InkJet Printers: Non-impact printers spraying microscopic liquid ink droplets.
  • Laser Printers: High-speed electrostatic drum printers using dry toner powder.
  • Audio Output: Computer speakers converting digital sound streams into physical sound waves.

System Software Infrastructure and Operating Systems

• Classification of Software
  • System Software: Low-level operational programs that manage basic internal hardware operations, control peripheral devices, interface with application software, and allocate system resources.
  • Application Software: Software constructed to perform specific tasks, solve real-world user problems, enhance productivity, or provide entertainment.

• Fundamental System Software Layers

  • Operating System (OS): Master system platform managing all computer operations.
  • Device Drivers: Specialized control routines translating high-level commands into peripheral signals.
  • Utility Programs: Maintenance utilities optimized for diagnostic management, system tuning, and security.
  • Program Translators: Software tools converting user-written code into machine instructions.

• Operating System Core Architecture

  • Functions as the low-level master control infrastructure necessary for running any general-purpose hardware.
  • Abstracts hardware complexities so application programs can execute without needing specific hardware-level configurations.
  • Applications are specifically coded to run on top of a designated target Operating System.

Operating System Functions and Booting Process

• The Booting Process
  • The essential initialization sequence that loads the operating system core into the main RAM memory upon system startup:
  1. Power-On: Electrical power supplied to system unit circuitry.
  2. Hardware Diagnostics: Microprocessor automatically executes diagnostic testing routines on CPU registers, RAM memory chips, and connected hardware peripherals.
  3. BIOS Execution: System executes the Basic Input/Output System (BIOS) startup code stored inside non-volatile ROM chips. BIOS contains core routines required to control hardware peripherals and locate system boot media.
  4. OS Loading: The startup boot program reads the operating system files off the primary hard disk, loads them into high-speed RAM main memory, and transfers total system execution control over to the OS kernel.

• Primary Operating System Functions

  • CPU Management & Kernel Control: Managed by the Supervisor (or Kernel), which stays permanently loaded in RAM while running. It coordinates non-resident routines to perform support actions for running applications.
  • Memory Allocation & Virtual Memory: Tracks all RAM memory addresses, ensuring active programs and data structures do not overlap. Dynamically swaps execution blocks between RAM and disk storage to manage virtual memory space.
  • Hierarchical File Management:
  • Organizes secondary storage containing Data Files (named collections of data) and Program Files (executable code files).
  • Structures data into a logical hierarchical tree format: top-level Directories (Folders) $\rightarrow$ Subdirectories $\rightarrow$ Files.
  • Files are precisely referenced via exact storage pathnames (e.g., C:/MyDocuments/Termpaper/section1.doc).
  • Task Management & Multitasking: Coordinates processing schedules, enabling computers to run multiple operations concurrently. Employs processing time-slicing across active applications (e.g., word processing while playing audio files).
  • Security & Access Control: Enforces system authorization boundaries by forcing user identity validation using pre-configured User IDs and Passwords during startup.
  • Resource Allocation: Continuously monitors hardware utilization, allocating processor execution times, storage slots, system memory blocks, and peripheral device traffic.

• Desktop Operating System Environments

  • Microsoft Windows Platform: Windows CE, Windows 2000, Windows Vista, Windows XP, Windows 7, Windows 8, Windows 10.
  • Apple Macintosh Platform: Mac OS X.
  • Linux Platform: Debian, RedHat, Ubuntu.

• Mobile Operating System Environments

  • Symbian OS, Palm webOS, iOS 4, BlackBerry (RIM), Windows Phone 7, Android.

System Utilities, Device Drivers, and Program Translators

• Utility Programs

  • Dedicated software applications engineered to assist in configuring, analyzing, optimizing, or maintaining optimal computer system health and file administration.
  • File Manager: Organizes, copies, moves, and tracks files and directory structures.
  • Uninstaller: Safely strips out software files, settings, and registry keys.
  • Antivirus Utility Suites: Scans system memory and storage to quarantine software threats (e.g., Avast, AVG Internet Security 2013, McAfee, Norton by Symantec, Kaspersky Lab).
  • File Compression Tools: Reduces overall file size footprints for transit or storage (e.g., 7-Zip, WinRAR).
  • Pop-Up Blockers: Filters out intrusive browser windows.
  • Backup Utilities: Performs scheduled disk backups to external target storage (e.g., PC Backup).
  • Firewalls: Filters network traffic parameters to block unauthorized connections.

• Device Drivers

  • Specialized system programs designed to allow operating systems to interact directly with external hardware peripherals (printers, scanners, input adapters).

• Program Translators

  • Converts high-level human-readable programming language source code (e.g., C++, Java) into machine-understandable binary execution code (machine code).

Application Software Categories, Licensing Models, and Suites

• Standard Application Software Types

• Distribution and Deployment Categories

  • Generic / Off-the-Shelf Packages: Pre-written, commercially packaged applications targeting widespread, general-purpose organizational tasks (e.g., standard word processors).
  • Custom / Bespoke Software: Tailor-made applications created specifically for a targeted organization or enterprise system (e.g., BTC billing system, UB student management system).
  • Open Source Software: Software provided with completely accessible source code downloadable from the internet, allowing universal modification, enhancement, and redistribution (e.g., Moodle, Linux, FrontlineSMS, WordPress).
  • Web Application Software: Hosted applications running on remote Internet cloud servers accessed through local web browser interfaces (e.g., Dropbox, Google Docs).
  • In-House Applications: Custom tools written internally using an organization's proprietary IT department resources.

• Licensing and Commercial Models

  • Proprietary Software: Commercial software distributed under strict legal rights owned exclusively by the developer; unauthorized distribution or copying is prohibited.
  • Rentalware: Online subscription software leased for recurring fees and downloaded on demand.
  • Freeware: Copyrighted software distributed completely free for user operation; users are forbidden from reselling it for commercial profit.
  • Shareware: Copyrighted software provided free for a temporary trial period, after which users must pay a registration fee for continued usage and upgrade support.
  • Integrated Software Packages (Software Suites): Bundled multi-application suites featuring common interface layouts, shared toolbars, and seamless data interchange.
  • Prominent Examples: Microsoft Office 2010, Corel WordPerfect Office X7, Apache OpenOffice.