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Informatics Practices: Class 11 — Chapter 1: Computer System

Introduction to Computer System

A computer is an electronic device that can be programmed to accept data (input), process it, and generate a result (output). A computer along with additional hardware and software together is called a computer system.

Central Processing Unit (CPU)

The CPU is the electronic circuitry of a computer that carries out the actual processing and is usually referred to as the brain of the computer. It is commonly called a processor.

Technical Profile: Central Processing Unit (CPU)

  • Architecture Layer / Tier: Core Hardware Processing Layer
  • Operational Mechanics: Fetches instructions and data from memory, performs arithmetic and logical operations, and stores results back to memory. Uses local high-speed memory called registers .
  • System Impact & Execution Outputs: Comprises the Arithmetic Logic Unit (ALU) for mathematical/logical operations and the Control Unit (CU) for sequential instruction execution and data flow control.
Input and Output Devices

Devices that facilitate interaction between the user and the computer system:

  • Input Devices: Convert input data into digital form. Examples: Keyboard , Mouse , Scanner , Touch Screen , and specialized Braille keyboards .
  • Output Devices: Convert digital information into human-understandable form. Examples: Display monitor , Speaker , Printer (Inkjet, Laserjet, Dot matrix, and 3D printer ), and Braille display monitors .
Evolution of Computer

Computing devices have evolved from simple mechanical calculators to modern high-speed processors. The Von Neumann architecture forms the basis of modern computers, consisting of a CPU, memory, input/output devices, and communication channels.

Timeline of Key Inventions
  • Abacus (500 BC): Mechanical device for simple arithmetic calculations.
  • Pascaline (1642): Mechanical calculator invented by Blaise Pascal for addition, subtraction, multiplication, and division.
  • Analytical Engine (1834): Designed by Charles Babbage; introduced input, processing, storage, and output concepts.
  • Tabulating Machine (1890): Designed by Herman Hollerith for summarizing data on punched cards.
  • Turing Machine (1937): General-purpose programmable machine concept by Alan Turing.
  • EDVAC/ENIAC (1945): First binary programmable computers based on the stored-program concept.
  • Transistor (1947): Replaced vacuum tubes, highly reducing size and power consumption.
  • Integrated Circuit (1970): Silicon chips containing entire electronic circuits.
Moore's Law and Modern Scaling

Technical Profile: Moore's Law & Silicon Scaling

  • Architecture Layer / Tier: Semiconductor Physics & Hardware Engineering
  • Operational Mechanics: Predicted that the number of transistors on a microchip doubles approximately every two years while the cost is halved.
  • System Impact & Execution Outputs: Led to the transition from Large Scale Integration (LSI) to Very Large Scale Integration (VLSI) and Super Large Scale Integration (SLSI), enabling modern smartphones, IoT, and AI.
Computer Memory

Computer memory is required to store data and instructions for processing. It is broadly categorized into primary and secondary memory.

Units of Memory

Data is stored in binary format using bits (0 and 1). A group of 4 bits is a nibble , and 8 bits is a byte .

Unit Description Unit Description
KB (Kilobyte) 1 KB = 1024 Bytes PB (Petabyte) 1 PB = 1024 TB
MB (Megabyte) 1 MB = 1024 KB EB (Exabyte) 1 EB = 1024 PB
GB (Gigabyte) 1 GB = 1024 MB ZB (Zettabyte) 1 ZB = 1024 EB
TB (Terabyte) 1 TB = 1024 GB YB (Yottabyte) 1 YB = 1024 ZB
Types of Memory
  • Primary Memory: Directly accessed by the CPU. Includes volatile RAM (Random Access Memory) and non-volatile ROM (Read Only Memory) .
  • Cache Memory: High-speed memory placed between the CPU and primary memory to speed up access to frequently used data.
  • Secondary Memory: Non-volatile, high-capacity storage. Examples: HDD (Hard Disk Drive) , SSD (Solid-State Drive) , CD/DVD , and Pen Drives .
Data Capturing, Storage, Retrieval, and Recovery

The lifecycle of digital data involves several critical phases:

  1. Data Capturing: Gathering data from sources (e.g., barcode readers, remote sensors).
  2. Data Storage: Saving captured data on digital storage devices or data servers.
  3. Data Retrieval: Fetching data from storage devices for processing.
  4. Data Deletion and Recovery: Deleting data marks its address space as free without immediate physical erasure. Data recovery tools can retrieve this data unless it is overwritten.
Software

Software is a set of instructions that makes the hardware functional. It is categorized into system software, programming tools, and application software.

System Software

Provides basic functionality to operate a computer by interacting directly with the hardware.

  • Operating System (OS): Manages system resources and provides a user interface (e.g., Windows, Linux, macOS, Android).
  • System Utilities: Used for maintenance and configuration (e.g., disk defragmentation, anti-virus).
  • Device Drivers: Act as translators between the OS and specific hardware peripherals.
Application Software

Software designed to perform specific tasks for users.

  • General Purpose Software: Developed for generic applications (e.g., word processors, spreadsheets like LibreOffice Calc , web browsers).
  • Customised Software: Tailor-made to meet the requirements of a specific organization or individual (e.g., school management systems).
Software Licensing Models

Technical Profile: Software Licensing & Distribution

  • FOSS (Free and Open Source Software): Software that is freely usable, and its source code is open for modification (e.g., Ubuntu, Python).
  • Freeware: Freely available software, but the source code is not accessible (e.g., Skype, Adobe Reader).
  • Proprietary Software: Purchased software with restricted usage rights and closed source code (e.g., Microsoft Windows, Tally).