Introduction to Computer Systems

INTRODUCTION TO COMPUTER SYSTEMS

Definition of a Computer

  • A COMPUTER is a programmable electronic device that processes data based on a set of instructions given by the user or a program.

  • Computers can take different forms:

    • Desktop computers

    • Laptop computers

    • Simple devices such as calculators.

  • Example: A calculator accepts two numbers, 6 and 10 (input), adds them (process), and displays the result ‘16’ (output).

  • Question posed: Can you think of any other devices that can be considered a computer?

Computer System

  • A computer never works alone; it is part of a COMPUTER SYSTEM.

  • A COMPUTER SYSTEM is a collection of devices and programs that work together with the computer to process data.

  • The main purpose of a computer system is to process raw facts and figures (referred to as data) into meaningful information, which can be outputted or stored for future use.

  • Processing Stages:

    1. Input: Data enters the system.

    2. Processing: Data is manipulated.

    3. Output: Results are displayed or stored.

FUNCTION OF COMPUTERS

Overview

  • This section discusses the fundamental operations of computers via the interaction of different components:

    • Processor (CPU): Executes instructions.

    • Input devices: Receive data and instructions from the user.

    • Output devices: Display or produce results for the user.

Processing Cycle

  • Diagram representation (illustration not included in the text):

    • Input ➔ Process ➔ Output

  • Stages also include:

    • Storage: Temporary and permanent data retention.

    • Feedback: Information returned to system or user for modification or confirmation.

COMPUTER SYSTEM COMPONENTS

Hardware and Software

  • A computer requires both HARDWARE and SOFTWARE to perform tasks.

Hardware

  • HARDWARE refers to all the parts of the computer system that you can see and feel.

Software

  • SOFTWARE consists of a set of instructions that a computer needs to carry out its tasks.

Classification of Computer Hardware

  • Computer hardware can be classified into four categories based on their purpose:

    1. Input: Devices used to enter data and instructions into the computer for processing.

    2. Processing: The processor (often referred to as the 'brain' of the computer) that converts data into meaningful information.

    3. Output: Devices that convert information processed by the computer into a human-readable format.

    4. Storage: Media or devices that a computer uses to keep data instructions available for immediate or future use.

INPUT HARDWARE

Definition of Input

  • Input is any data or instruction entered into the computer system.

  • Specialist devices used to enter data are called INPUT DEVICES.

Examples of Input Devices

  • Common Examples:

    • Keyboard

    • Mouse

    • Barcode scanner

    • Trackball

  • Additional devices include:

    • Joysticks

    • Microphones

    • Stylus

    • Touch screens

Categories of Input Devices

  • Input devices are divided into three categories:

    1. Key Input Devices: Utilize keys for data entry (e.g., keyboard).

    2. Point and Draw Devices: Used to select or manipulate objects on-screen (e.g., mouse, joystick).

    3. Source Data Automation: Inputs data directly into the computer in a machine-readable format (e.g., scanner, microphone).

POINT AND DRAW DEVICES

Key Input Device

  • Key Input Devices: This category consists only of the keyboard, which has rows of keys used to enter alphanumeric characters or execute functions.

Point and Draw Devices

  • Devices in this category include:

    • Mouse: Controls the movement of the on-screen pointer/cursor.

    • Joystick: Used in gaming; it consists of a vertical handle that translates movement into commands.

    • Trackball: A stationary device with a rolling ball, often providing more precision than a mouse.

    • Stylus: Reacts to touches on touch-sensitive screens.

    • Touch Screen: A display that detects input through direct touch.

    • Touch Pad: Found mostly on laptops, allows for pointer control via finger movements.

SOURCE DATA AUTOMATION DEVICES

Definition

  • Source data automation devices input audio, video, or documents directly into the computer without the use of traditional input methods.

Examples

  • Common examples include:

    • Scanner: Reads images or text for digital conversion.

    • Barcode Reader: Scans barcodes for data entry.

    • Digital Camera: Captures images or videos.

Specific Device Descriptions

  • Scanner: Uses light to read physical documents and convert to digital format.

  • Barcode Reader: Reads patterns on barcodes and converts them into data.

  • Microphone: Converts sound into digital data.

  • Optical Character Reader (OCR): Scans printed text and converts it into electronic data.

  • Magnetic Ink Character Reader (MICR): Reads printed characters for documents, commonly used in banking.

PROCESSING HARDWARE

The Central Processing Unit (CPU)

  • The CPU is defined as the 'brain' of the computer.

  • It transforms raw data into information through several functions:

    • Performs calculations.

    • Coordinates all activities of the computer.

Data vs. Information

Definitions

  • DATA: Raw, unorganized facts and figures requiring processing to gain meaning.

  • INFORMATION: Processed data that holds meaning within context. Example: Student ages are mere data until labeled as "Ages of students in class X".

Processing Speed

  • Measured in Megahertz (MHz) or Gigahertz (GHz).

  • Higher numbers denote faster processing speeds, impacting computer performance.

Components of the CPU

  • The CPU consists of three main components:

    1. Control Unit (CU): Directs input/output operations and ensures correct data processing.

    2. Arithmetic and Logic Unit (ALU): Performs mathematical calculations and logical comparisons.

    3. Registers: High-speed storage areas that temporarily hold data and instructions during processing.

OUTPUT HARDWARE

Definition of Output

  • Output devices present processed information to users in understandable formats.

Categories of Output

  • Information can be output in forms:

    1. Text

    2. Graphics

    3. Audio

    4. Video

Hard Copy vs. Soft Copy Output

  • Hard Copy Output: Permanent output printed on paper; retains information without power.

  • Soft Copy Output: Non-permanent display on screens; lost when powered off unless saved.

HARD COPY OUTPUT DEVICES

Printers

  • Divided into two broad categories:

    1. Impact Printers: Use mechanical impact to produce output (e.g., Dot Matrix, Line Printers).

    2. Non-Impact Printers: Use technology like heat and ink (e.g., Laser, Inkjet).

Impact Printers

  • Line Printer: Outputs an entire line at once, best for high-volume print jobs. Lacks graphics capability.

  • Dot Matrix Printer: Prints character by character, slower and noisier, suitable for low-quality printing.

Non-Impact Printers

  • Laser Printer: Utilizes laser technology for high-quality, faster output; commonly found in offices.

  • Ink Jet Printer: Produces good quality images using tiny ink droplets; less quality than lasers but preferred for home use.

  • Thermal Printer: Utilizes heat for printing on special papers; known for low operational costs and quiet functionality.

Plotters

  • Specialized printers for large-format drawings, often used in architecture and engineering; more expensive than standard printers.

SOFT COPY OUTPUT DEVICES

Types

  • Monitor: Primary output device displaying tasks being executed; two main types: CRT and LCD.

  • Projector: Projects images on larger surfaces for presentations.

  • Speakers/Headphones: Output audio generated by the computer, linked to sound hardware.

STORAGE HARDWARE

Definition of Storage

  • Storage devices retain data for immediate or future use. They can be categorized into:

    1. Primary Storage

    2. Secondary Storage

Primary Storage

  • Primary Storage (Main Memory): Stores data that the CPU manipulates and executes, characterized as volatile.

Types of Primary Storage

  • Random Access Memory (RAM): Holds active data temporarily, lost when power is off.

  • Read-Only Memory (ROM): Permanently stores critical data, resistant to power loss; may be rewritten in newer versions.

Secondary Storage

  • Secondary Storage: Retains data long-term, non-volatile (information remains after power loss).

Types of Secondary Storage

  1. Magnetic Storage: Uses magnetization patterns to store data (e.g., hard drives, floppy disks).

  2. Optical Storage: Uses lasers to read and write data on media (e.g., CDs, DVDs).

  3. Solid State Storage: Retains data electronically using flash memory, recognized for its portability and speed (e.g., USB drives).

Comparison of Primary and Secondary Storage

  • Price: Primary is more expensive; secondary is more affordable.

  • Volatility: Primary storage is volatile (RAM) and semi-volatile (ROM); secondary is non-volatile.

  • Data Storage Method: Primary stores data electronically; secondary uses magnetic, optical, or electronic means.

  • Storage Capacity: Primary storage is limited; secondary storage can be extensive.

  • Access Speed: Primary storage is faster than secondary storage, with RAM located directly on the motherboard, while secondary storage is connected by cables.