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Basic Computer Science ​

Computer science is a field of study that encompasses the theory, design, development, and application of software and software systems. It is not solely about programming but includes a broad range of topics related to computing.

What is a Computer System? ​

A computer system is a programmable digital electronic device that accepts input in the form of data, processes this data based on program instructions, and outputs information in a desired format for meaningful use. Its two main characteristics are that it responds to a specific set of instructions in a well-defined manner and it can execute a pre-recorded list of instructions (a program). Modern computers are electronic and digital.

Main Functions of a Computer System ​

A computer primarily performs the following four basic functions:

  • Receive input: Accepts data/information from outside through various input devices like the keyboard, mouse, or scanner.
  • Process information: Performs arithmetic or logical operations on data/information. This involves converting raw data into useful information.
  • Produce output: Communicates information to the outside world through output devices like a monitor or printer.
  • Store information: Stores information in storage devices like hard disk, floppy disks, or CD for future use.

Components of a Computer System ​

A computer system comprises two major components: hardware and software. They are interdependent, meaning software needs hardware to run, and hardware is useless without software. Software sends instructions to hardware for tasks like printing or saving files.

Hardware ​

Hardware refers to the physical components of the computer that can be seen and touched. Key hardware components include:

  • Central Processing Unit (CPU): Often called the "brain" or "heart" of the computer, it is the component that actually executes instructions and processes data. It controls all operations and performs calculations.
    • Control Unit (CU): Manages and coordinates the entire computer system. It tells the rest of the system how to carry out program instructions and directs the movement of electronic signals between memory, the ALU, and input/output devices.
    • Arithmetic Logic Unit (ALU): Performs arithmetical operations (addition, subtraction, multiplication, division) and logical operations (comparisons).
    • Registers: Special high-speed storage areas within the Control Unit and ALU that temporarily hold data and instructions during processing.
  • Memory Unit: The electronic device that holds data and instructions for processing. It consists of binary cells (0s and 1s) to store information. Memory is categorized into:
    • Primary Memory (Main Memory): Accessible directly by the CPU and used for temporary storage of data and instructions in use. It has low memory capacity but high processing speed.
      • Random Access Memory (RAM): Volatile memory where data is lost when the power goes off. When a computer starts, operating system files and basic programs are loaded into RAM.
      • Read-Only Memory (ROM): Non-volatile memory where information is permanently stored and retained even when power is off. ROM stores standard processing programs supplied by manufacturers and can only be read by the CPU.
      • PROM (Programmable Read-Only Memory): A variation of ROM where data can be written only once.
      • EPROM (Erasable Programmable Read-Only Memory): Information stored in an EPROM chip can be erased and reprogrammed using a special device.
      • EAPROM (Electrically Alterable Programmable Read-Only Memory): Similar to EPROM, but memory can be altered using electrical signals without erasing the whole memory.
      • Cache Memory: A small, expensive memory chip attached between the CPU and main memory to reduce the mismatch in operating speed. It stores frequently used programs or data.
    • Secondary Memory (Auxiliary Memory): External source of memory for long-term data storage, typically with low cost per bit of storage but slower operating speed than primary memory. Examples include:
      • Hard Disk Drives (HDD) and Solid-State Drives (SSD).
      • USB flash drives/Pen Drives.
      • Floppy Disk: A portable, low-cost device with a capacity of 1.44 megabytes.
      • CD-ROM/CD-R/CD-RW: Optical disks used to store digital data, music, video, and pictures (up to 700MB).
      • Magnetic Tape: Very large storage capacity (20 GB to 2 TB) used for backup.
      • Blue-Ray Disk: Optical medium capable of storing 25 GB per single layer and 50 GB per dual layer.
  • Input Devices: Devices used to enter data/instructions into the computer. Examples include keyboard, mouse, scanner, microphone, joystick, touch screen, light pen, and webcam.
  • Output Devices: Devices that display or output data from the computer in a human-understandable form. Examples include monitor/display screen, printer (inkjet, laser, dot matrix, 3D), speaker, and headphones.
  • Motherboard: The main circuit board that connects all components of the computer, housing the CPU, memory, and other essential components.
  • Power Supply: Provides power to the computer's internal components.
  • Computer Buses: Facilitate communication between components.

Software ​

Software refers to the set of instructions, data, or programs used to operate computers and execute specific tasks. It is intangible and exists as digital data. Software activates hardware to perform specific tasks.

  • System Software: The software necessary to run a computer and control/coordinate programs. It enhances hardware utilization efficiency and makes computers simpler to use.
    • Operating System (OS): A set of programs that manages computer hardware and provides services for computer programs. It acts as a medium between the user and the computer. Examples include Windows, Linux, MacOS, Android, and iOS. Functions include memory management, file management, input/output management, user interface, and providing utilities.
    • Utility Programs: Such as antivirus and disk cleanup.
    • Programming Language: Tools to write instructions for computers.
    • Language Translator: System software that translates a computer program written by a user into a machine-understandable form. This includes compilers and interpreters.
  • Application Software: Programs written in high-level languages for specific problems or user needs. Examples include MS Office, web browsers, games, word processing, inventory control, and railway reservation systems.
  • Programming Software: Used for coding and software development.

Computer Languages ​

Programming languages are formal languages used to give instructions to a computer and develop software. They are classified into:

  • Low-Level Language: Closer to hardware and written in machine code or assembly language.
    • Machine Language: Consists of binary code (0s and 1s) directly understood by computer hardware. It is difficult to write and understand.
    • Assembly Language: Uses symbolic codes and abbreviated instructions (mnemonic codes), making it easier to read and write than machine language. It needs to be converted to machine code for execution.
  • High-Level Language: Easier for humans to read and understand, requiring a compiler or interpreter for execution. They are generally machine-independent. Examples include C, C++, Java, Python, Pascal, Fortran, JavaScript, PHP, Ruby, SQL, Prolog, and HTML.
    • Procedural Languages: (e.g., C, Pascal, Fortran).
    • Object-Oriented Languages: (e.g., C++, Java, Python).
    • Scripting Languages: (e.g., JavaScript, PHP, Ruby).
    • Declarative Languages: (e.g., SQL, Prolog, HTML).
  • Compiler: Translates the entire high-level program into machine language before execution.
  • Interpreter: Executes the code line by line.

Data Processing Concepts ​

Data processing involves converting raw data (a collection of facts) into useful information (transformed data presented in a meaningful and concise form). The data processing cycle includes:

  • Collection: Gathering raw data.
  • Conversion: Changing data into a machine-readable form (e.g., binary).
  • Manipulation: Performing operations like classifying, sorting, calculating, and summarizing.
  • Storage and Retrieval: Filing data and information for future use.
  • Communication: Transmitting processed information.

Evolution of Computers ​

The development of computers can be categorized into generations based on technological advancements:

  • First Generation (1940-1956): Used Vacuum Tubes as the main technology. Operated with machine language and punch cards. Examples include ENIAC and UNIVAC-I. They were large, consumed much electricity, and generated significant heat.
  • Second Generation (1956-1963): Featured Transistors, making them smaller, faster, and more energy-efficient than vacuum tubes. Assembly language was used. Examples: IBM 1401.
  • Third Generation (1964-1971): Introduced Integrated Circuits (ICs), combining multiple transistors on a single silicon chip. Operating systems were developed to manage hardware and software, enabling multitasking.
  • Fourth Generation (1971-1989): Characterized by Microprocessors and Very Large Scale Integration (VLSI), leading to personal computers. Introduced high-level programming languages and user-friendly interfaces.
  • Fifth Generation (1989-till date): Focused on developing computers with intellectual capacities like reasoning, thinking, and decision-making, with a goal of faster speed, greater reliability, and ability to work in unfavorable conditions.

Fundamentals of Computing ​

This area encompasses a wide range of concepts forming the basis of computer science and information technology.

  • Basic Computer Architecture: Includes CPU, Memory (RAM, ROM), Storage Devices, Input/Output Devices, and Motherboard.
  • Operating Systems: Software that manages computer hardware and provides services for programs.
  • Software Development: Involves programming languages and software engineering principles.
  • Data Structures and Algorithms:
    • Data Structures: Ways to organize and store data (e.g., arrays, lists, trees).
    • Algorithms: Step-by-step procedures for calculations, data processing, and automated reasoning. They must be efficient, correct, finite, and definite.
  • Databases: Systems for storing, retrieving, and managing data (Relational/SQL, Non-relational/NoSQL).
  • Networking: Connecting multiple computers to share resources and communicate, including concepts like LAN, WAN, protocols (TCP/IP), and network security.
  • Internet and Web Technologies: The global network of networks (Internet) and technologies for developing websites and web applications (HTML, CSS, JavaScript).
  • Human-Computer Interaction: Focuses on designing user-friendly interfaces.

Key Terminology ​

  • Bit: The smallest unit of memory, a binary digit, representing either 0 or 1.
  • Byte: Consists of 8 bits.
  • Volatile Memory: Memory that loses its content when power is removed (e.g., RAM).
  • Non-Volatile Memory: Memory that retains data even when power is off (e.g., ROM, HDD, SSD).
  • Moore's Law: Proposed by Gordon Moore in 1965, it predicted that the number of transistors on a chip would double every two years while costs would be halved.
  • Digital Signal: A signal that takes only particular finite number of amplitude values, typically ‘0’ and ‘1’.
  • Punched Card: A piece of stiff paper that stores digital data in the form of holes at predefined positions.