computer science

• Components of a computer system


  • Inputs
  • Processes
  • Storage
  • Outputs
• Input devices


  • Mouse
  • Keyboard
  • Microphone
  • Camera
  • Scanner
• Output devices


  • Monitor
  • Speakers
  • Headphones
  • Printer
  • LEDS
• Hybrid devices


  • 2in1 Printer Scanner
  • Bluetooth headset
  • Smart Phone
  • Tablets
  • Touch Screen
• Accessibility


  The design of hardware or software for people who experience disabilities
• Accessibility features for visual impairment


  • On screen magnifier
  • Braille Display
• Accessibility features for dexterity issues


  • Touch Screen
  • On Screen Keyboard
• Accessibility features for hearing impairment


  • Subtitles
  • Classroom Hearing Aid
• Accessibility features for learning disabilities


  • Opendyslexic
  • Speech to Text
  • Text to Speech
• Hardware


  The parts of a computer that can be touched
• Internal computer components


  • Motherboard
  • CPU
  • Power Supply Unit
  • RAM
  • Hard-Drive or SSD
  • GPU
  • Optical Drives (Optional)
• Computer case


  The enclosure that all the components are fitted into, protecting the components and allowing for airflow to cool the computer
• Power Supply Unit (PSU)


  Takes in voltages from the mains, transfers it to DC energy (from AC) and distributes the power through the computer system
• Motherboard


  A circuit board that connects the CPU to the memory and all the other hardware, the CPU sits on the Motherboard
• Graphical Processing Unit (GPU)


  Renders images, animations and video for the computer's screen, can be a plug-in card or integrated into the CPU
• Optical Drives


  Allow a computer to read discs such as CDs, DVDs and Blu-ray Discs
• Central Processing Unit (CPU)


  The brain of the computer, processes all the data for every action the user takes
• Random Access Memory (RAM)


  Stores active parts of programs that are running on the computer, all data is forgotten if there is no power
• Hard Disk Drives (HDDs)


  Storage devices used to store the Operating system, installed programs and user data, information is not forgotten if there is no power
• Embedded Systems


  Computers inside objects that are dedicated to one fixed purpose
• Examples of Embedded Systems


  • Microwave
  • Washing Machine
  • Traffic Light
  • Digital Watch
  • Satnav
  • Household Phone
• Embedded Systems


  • Smaller than regular computers
  • Cheap to make as they only have one purpose
  • Designed to perform a dedicated task, won't slow down as they are not running multiple programs at once
• Main components of the CPU


  • CU-Control Unit
  • ALU-Arithmetic Logic Unit
  • Cache
• Control Unit (CU)


  In overall control of the whole CPU, controls data flowing both inside and outside of the CPU, executes program instructions
• Arithmetic Logic Unit (ALU)


  Where the CPU performs arithmetic and logic operations (AND, OR, NOT), every task the computer carries out is completed here
• Cache


  Very fast piece of memory inside the CPU, stores regularly used data for quick access, checked first before accessing RAM
• Cache levels


  • L1 - Quickest but Low Storage
  • L2 - Slower but Higher Storage
  • L3 - Slowest but Highest Storage
• Registers


  Small stores of data in a CPU that hold a single number or instruction, size depends on the operating system
• Von-Neumann Architecture


  The architecture of the modern CPU, housing registers in the various components
• Program Counter


  Holds the memory address of the instruction for the current cycle, counts the steps of the program
• Accumulator


  Stores intermediate results of calculations in the ALU
• Memory Address Register (MAR)


  Holds any memory address about to be used by the CPU, the address might point to data or a CPU instruction
• Memory Data Register (MDR)


  Holds the actual data or instruction, may have been fetched from memory or be waiting to be written to memory
• Fetch-Decode-Execute Cycle


  1. Copy memory address from program counter to MDR

  2. Copy instruction stored in MAR address to MDR

  3. Increment program counter

  4. Decode instruction

  5. Execute instruction
• Primary Memory


  Volatile storage that stores active parts of programs running in the computer, faster than secondary memory but less storage
• Secondary Memory


  Non-volatile storage that stores whole programs, start-up information and operating systems, slower than primary memory but more storage
• Read Only Memory (ROM)


  Non-volatile memory that holds the BIOS, a set of instructions which starts the computer and initiates the operating system
• Random Access Memory (RAM)


  Primary storage, volatile, stores active parts of programs from the hard drive/SSD for fast access by the CPU
• BIOS


  Manages the start-up of a computer system, allows the user to change which drive the OS is read from and provides system information and tweaking
• RAM and performance


  • More RAM means more information can be held at one time (more programs simultaneously)
  • Faster RAM means information can be accessed faster for processing