Computer Science

• 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
• Combined, these only cover a couple of square centimetres, but can hold several million transistors and process hundreds of millions of instructions per second
• 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

  • Controller
  • 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
• Types of registers


  • Accumulator
  • Program Counter (PC)
  • Memory Address Register (MAR)
  • Current Instruction Register (CIR)
• Buses


  Allow data to be transferred to different parts of the computer
• Types of buses


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


  1. Fetch cycle

  2. Decode cycle

  3. Execute cycle
• CPU cache memory


  Fast access type of memory that improves CPU performance
• Clock speed


  The speed at which a processor operates, measured in Hertz (Hz)
• Overclocking increases CPU clock speed, using more energy and producing more heat
• Underclocking decreases CPU clock speed, reducing power consumption and heat
• Some devices can dynamically change their CPU clock speed
• 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 screen
  • Barcode scanner
  • QR code scanner
• The first computer mouse was made of wood by Doug Engelbart in 1964
• Interactive whiteboards were developed long before touch screens
• 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. The use of barcode scanners speeds up the process of data input into a system.
• QR code


  Codes that can hold more data than barcodes, such as web addresses, contact details, calendar registrations and details of goods in factories and warehouses.
• Monitor


  An electronic visual computer display that includes a screen and the case in which all circuitry is enclosed. Most monitors used with devices such as laptops, PDAs and desktop PCs are made using LCD screens as they are lighter and more energy efficient.
• Speaker


  Used to produce audio output that can be heard by the listener. When they receive audio input from a device, the electromagnetic waves are converted into sound waves. Analog speakers amplify the analog electromagnetic waves into sound waves, while digital speakers must first convert the digital input into an analog signal, then generate the sound waves.
• Printer


  An output device that prints paper documents, including text, images, or a combination of both. The two most common types are inkjet and laser printers.
• Projector


  An output device that projects an image onto a large surface, such as a white screen or a wall. It may be used as an alternative to a monitor or a television when showing video or images to a large group of people.
• Basic Input/Output System (BIOS)

  A low-level program that handles input and output operations relating to the system's keyboard and screen. It provides an interface between the hardware and the operating system, and one of its primary functions is loading and executing the bootstrap loader.
• Random Access Memory (RAM)

  Used for the temporary storage of currently running programs and data, such as the operating system and a text editor program. It consists of a large number of store locations, each with a unique address, and the data in each store location can be changed. RAM is volatile - data is lost when the power is switched off.
• Read Only Memory (ROM)


  Used for the permanent storage of data. The data in each store location cannot be changed. ROM is permanent - data is not lost when the power is switched off.
• Flash memory


  Used for the permanent storage of data, but the data stored can be changed. Flash memory is permanent - data is not lost when the power is switched off.
• RAM Cache memory


  Used for the temporary storage of frequently accessed data and instructions. It consists of a small number of store locations that can be accessed very quickly by the CPU, and is quicker than RAM. Cache memory is volatile - data is lost when the power is switched off.