Intro to Computer Systems

Introduction to Computer Systems

• A computer is a programmable electronic device that accepts data (input), processes it, and generates results (output).
• A computer system is made up of hardware and software components that work together.
• Main components include the Central Processing Unit (CPU), memory, input/output (I/O) devices, and storage devices.
• Computer systems come in different sizes, from servers to smartphones.

Central Processing Unit (CPU)

• CPU is the electronic circuitry that executes instructions, often called the "brain" or processor.
• A CPU can be placed on integrated circuits (ICs), which are microchips made of semiconductor materials.

Input Devices

• Input devices send control signals to a computer
• Examples: keyboard, mouse, scanner, touch screen.
• Input devices convert data into a digital form that the computer understands.
• Voice input is possible via tools like Google voice search.
• Input data is temporarily stored in the main memory (RAM).
• Data and instructions are permanently stored in secondary memory for future use.

Output Devices

• Output devices receive data from a computer system for display or physical production
• Examples: monitor, projector, headphone, speaker, printer.
• These devices convert digital information into a human-understandable form.
• Braille displays provide output for visually impaired individuals.
• Common printer types include inkjet, laserjet, and dot matrix.
• 3D printers can create physical replicas of digital designs.

Evolution of Computers

• Computing devices have evolved from simple calculators to complex data processors.
• Key milestones:
  • Abacus (3000 BC): Early mechanical device for arithmetic calculations.
  • Pascaline (1642): Mechanical calculator invented by Blaise Pascal for addition and subtraction
  • Tabulating Machine (1890): Herman Hollerith's machine for summarizing data on punched cards; an early step towards programming.
  • Turing Machine (1937): A general-purpose programmable machine concept.
  • EDVAC/ENIAC (1945): John Von Neumann's concept of stored program computers capable of storing both data and programs in memory.
  • Transistor (1947): Developed at Bell Labs, transistors replaced vacuum tubes.
  • Integrated Circuit (IC) (1970): A silicon chip containing an entire electronic circuit; reduced computer size.
• The Von Neumann architecture includes a CPU, memory, input/output devices, and communication channels.
• ENIAC was the first binary programmable computer based on Von Neumann architecture.
• Moore's Law: The number of transistors on a chip doubles every two years, while costs are halved.
• Large Scale Integration (LSI) in the 1970's allowed the integration of a complete CPU on a single chip, called a microprocessor.
• Very Large Scale Integration (VLSI) in the 1980's integrated about 3 million components on a small chip.
• Super Large Scale Integration (SLSI): Made it feasible to fabricate high-density transistors and other components on a single IC.
• IBM introduced its first personal computer (PC) in 1981, and Apple introduced Macintosh in 1984.
• Graphical User Interface (GUI) based OSes increased PC popularity.
• Introduction of laptops, smartphones, and AI have further revolutionized computing

Computer Memory

• Computer memory stores data and instructions for processing.
• 'Memory' typically refers to main or primary memory.
• Secondary memory (storage device) stores data, instructions, and results permanently.

Units of Memory

• Binary digits (0 and 1) are the basic units of memory, called bits.
• A 4-bit word is called a nibble.
• An 8-bit word is called a byte.
• Bytes are grouped into larger units of memory.

Types of Memory

• Primary memory and secondary memory are categories.
• Primary memory is essential for a computer system because programs and data are loaded here before processing.
• Primary memory contains Random Access Memory (RAM) and Read-Only Memory (ROM).
  • RAM is volatile; data is retained as the power is supplied but is wiped out when power is turned off.
  • Program and data are loaded into RAM for processing.
  • ROM is non-volatile and content is not lost when the power is turned off.
  • ROM stores the startup program (boot loader).
• Cache memory is a very high-speed memory placed between the CPU and primary memory.
  • It stores copies of frequently accessed data from primary memory.
• Secondary Memory
  • It has limited storage capacity, either volatile (RAM) or read-only (ROM).
  • Computer systems need auxiliary or secondary memory to store data or instructions to preserve them for later.
  • Secondary memory is non-volatile.
  • Cannot be accessed by the CPU directly.
  • Examples: Hard Disk Drive (HDD), CD/DVD, Memory Card, Solid State Drive (SSD).

Data Transfer between Memory and CPU

• Data must be transferred between the CPU and primary or secondary memory.
• Data are transferred using physical wires called a bus.
  • Data bus transfers data.
  • Address bus transfers addresses.
  • Control bus communicates control signals.
• CPU places the address of the memory location on the address bus to read from or write data.
• A data bus is bidirectional for reading or writing to main memory, but control/address buses are unidirectional.
• The memory controller manages the flow of data into and out of the computer's main memory.

Microprocessors

• The CPU now fits on a single microchip
• A processor (CPU) on a single microchip is called a microprocessor.
• Microprocessors carry out data processing, arithmetic, and logical operations.
• Microprocessors are built over an integrated circuit and contain components like resistors, transistors, and diodes.
• Microprocessors have evolved to offer increased processing capability, reduced size, and reduced cost.

Microprocessor Specifications

• Microprocessors are classified by word size, memory size, clock speed, and cores.
  • Word Size: The maximum number of bits a microprocessor can process at a time.
  • Memory Size: The size of RAM varies depending on the word size.
  • Clock Speed: Refers to the number of pulses generated per second, indicating the speed at which the computer can execute instructions (GHz).
  • Cores: A basic computation unit of the CPU; multi-core processors can execute multiple tasks simultaneously.

Microcontrollers

• Microcontrollers are small computing devices that have a CPU, a fixed amount of RAM, ROM, and other peripherals all on a single chip.
• Examples: keyboard, mouse, washing machine, digital camera, pendrive, remote controller.
• Microcontrollers are embedded in another device or system to perform a specific function.

Data and Information

• A computer processes data, considering everything as data, to produce meaningful information.
• Data can be in the form of facts, concepts, or instructions.

Data Types

• Internally, data is stored in binary form (0 and 1).
• Externally, data can be input in text form or from files.
• Data can be structured, semi-structured, or unstructured.
  • Structured Data: Organized data in a strict record structure (e.g., tabular format).
  • Unstructured Data: Data that lacks a predefined record format (e.g., audio and video files, graphics).
  • Semi-structured Data: Data that have some organization and contain internal tags or markings.

Data flow

• Data is captured, stored, and retrieved for computer processing purposes
• Data Capturing: Gathering different types of data from different digital sources
• Data Storage: Consists of storing all captured data for processing later
• Data Retrieval: Consists of fetching data from storage devices for processing per the user's requirements

Data Deletion and Recovery

• Data can be deleted intentionally, accidentally, or due to malicious actions.
• Deleting data involves marking its address entry as free, but the data may still be recoverable.
• Data recovery can retrieve deleted, corrupted, or lost data from secondary storage devices.
• Security measures are needed to protect data from unauthorized deletion or recovery.
• Data should be shredded before disposing of old storage devices.

Software

• Software is the set of instructions that operates the hardware.
• The software comprises a set of instructions which on execution deliver the desired outcome
• Types of software:
  • System software
  • Programming tools
  • Application software.

System Software

• System software provides basic functionality such as running the computer system by interacting with the hardware.
• Provides services to the end user
• Examples: Operating Systems, Device drivers, System utilities

Operating System (OS)

• Is the most basic system software
• Manages applications programs and provides access and security to users
• Examples: Windows, Linux, Android, iOS

System Utilities

• System utility software is used for maintenance and configuration of the computer system
• Examples: Disk defragmentation tool, formatting utility, anti-virus software, and disk cleaner

Device Drivers

• Device drivers ensure proper functioning of a particular device
• It provides required services

Programming Tools

• Computer languages are developed for writing instructions
• Classification of Programming Languages
  • Low-level language
    • Machine language
    • Assembly language
  • High-level language
    • C++
    • Python
    • Java
• As the computer can only understand machine language
• Translators convert from high-level to machine language

Translators

• Assembler converts code into assembly language to machine language
• Compiler converts codes written in high-level language to machine understandable form for execution by the computer
• Interpreter translates one line at a time rather than the whole program

Application Software

• System software provides core function
• Application software meets the requirements of the end user
• Two broad categories of application software
  • General purpose. Examples: spreadsheet, GIMP
  • Customised applications
• The developers of some software provide their source code to the public to improve or develop. It is known as FOSS (Free and Open Source Software)
• Source code may not always be available, so it is known as freeware
• Proprietary software is used when software has to be purchased

Operating System

• Manages all resources within a computer such as CPU, RAM, Network and other devices

Types of User Interface of OS

• Command-based Interface: Requires the user to enter a command to perform a task like opening or deleting
• Graphical User Interface: Allows users to run programs using icons and menus
• Touch-based Interface: Smartphones use touch inputs
• Voice-based Interface: Modern computer designed for disabled or unable users
• Gesture-based Software: Use waving, tilting motion

Functions of Operating System

• Process Management
  • While the computer system is operation different tasks run simultaneously
• Memory Management
  • the main task of memory management is to give and take memory from running processes
• File Management
  • Data and programs are stored as files in the secondary stories

Device Management

• A computer system has I/O devices and hardware connected to it
• Operating system manages these different connected devices.