comp sci

• To a computer, the world consists of zeros and ones
• Transistor


  Microscopic switch that controls the flow of electricity depending on whether the switch is on or off
• A single silicon chip can contain thousands of transistors
• A single CPU contains a large number of chips
• CPU architecture


  The design of a Microprocessor, an integrated circuit, where the components of the CPU are combined as a single unit
• Von Neumann architecture


  The idea of storing the program instructions in the same memory as the data, resulting in computers that could be more easily re-programmed
• Components of the CPU

  • Control unit (CU
  • Arithmetic and Logic Unit (ALU)
  • Registers
  • Internal memory
• Controller


  Manages the execution of instructions
• Arithmetic and Logic Unit (ALU)


  Processes and manipulates data
• Register


  Fast access temporary data store
• Internal memory


  Fast access memory on the CPU
• Buses allow data to be transferred to different parts of the computer
• Main buses used by the CPU

  • Address bus
  • Data bus
  • Control bus
• Fetch-decode-execute cycle


  1. Fetch cycle

  2. Decode cycle

  3. Execute cycle
• Cache memory


  Fast access type of memory
• Clock speed


  The speed at which a processor operates, measured in Hertz (Hz)
• Overclocking increases the clock speed of the CPU, using more energy and producing more heat
• Underclocking decreases the clock speed of the CPU, resulting in less power consumption and less heat
• Core


  The processing components within the CPU

  
• Multi-core processors have many processing components within the same CPU
• RISC processor


  Processes a limited number of relatively simple instructions
• CISC processor


  Processes a large number of complex instructions
• Common hardware input devices

  • Mouse
  • Trackball
  • Computer keyboard
  • Concept keyboard
  • Microphone
  • Digital camera
  • 2D scanner
  • 3D scanner
  • Interactive whiteboard
  • Touch screens
  • Barcode scanner
  • QR code scanner
• The mouse allows the user to control the co-ordinates and movements of a cursor on the computer screen
• A trackball is an input device similar to a mouse, but the ball remains stationary and the user moves the cursor by moving the ball around
• Computer keyboards are used to input data and commands into the computer by pressing the keys
• Concept keyboards have images on each key to represent commands
• A microphone converts analogue sound waves into electrical signals understood by the computer
• A digital camera uses an image sensor and a chip to capture images digitally
• 2D scanners convert documents or 2D images into digital files
• 3D scanners generate a 3D model of a scanned object using x-ray, laser, light or sound waves
• An interactive whiteboard is used in classrooms and can be used for navigation, writing and designing
• A touch screen is a digital visual display that also works as an input device that responds to the user's touch
• Barcode scanners speed up the process of data input by scanning barcodes
• QR code scanners can scan QR codes to access data like web addresses, contact details, calendar registrations and details of goods
• Touch screen


  A digital visual display that also works as an input device that responds to the user's touch. It allows users to make selections by touching the screen.
• Barcode


  A code that can be read by a machine, represented by a series of black and white lines that represent numbers from 0 to 9
• Barcode scanner


  A device that speeds up the process of data input into a system by scanning barcodes, e.g. scanning items at a checkout desk in a supermarket
• QR code


  A code that can hold more data than barcodes, e.g. web addresses, contact details, calendar registrations and details of goods in factories and warehouses
• QR code scanner


  A device that can scan QR codes by taking a picture of them