Paper 2 computer science AQA

• What is a CPU?

  The CPU is essentially the brains of a computer which handles all of the processes and responses.
• What are the three characteristics of CPu's that effect its peformance?

  -Clock Speed

  -Cache Size

  -Number Core
• Clock Speed


  -Measured in Hertz

  -IS the number of cycles per second

  -Dictates the number of instructions the processor can take
• Cache Size


  -fast memory that stores most commonly used instructions

  -Stores copies of recent data and instructions

  -Much quicker at getting items from cache than RAM
• Number of Cores


  -A core is a complete copy of a CPu

  -Doubling the number of cores doesnt double the overall speed

  -CPU cores have to communicate with ech other this takes time
• Name all the CPU components

  -ALU

  -Control Unit

  -Cache

  -Clock

  -Registers

  -Buses
• Name and describe three of the CPU compenents

  -Arithemtic logic unit

  this performs arithemetic calculations and makes logical decisions

  -Cache

  this provides fast access to frequently used instructions and data

  -Buses

  wires that transmit data and instructions from one component to another
• ALU?


  Arithmetic and Logic Unit - does all mathematical calculations and makes all logical decisions
• Control unit?


  it fetches, decodes and executes instructions and moves data around the systems
• Cache (CPU cache)


  provides fast access to frequently used instructions and data
• Clock (CPU)


  The electronic unit that synchronises related components by generating pulses at a constant rate
• Registers (CPU)


  tiny super-fast pieces of onboard memory inside the CPU each with a specfic purpose
• Buses (CPU)


  wires that transmit data and instructions from one component to another
• Fetch-Decode-Execute Cycle


  The process that the CPU uses to retrieve and execute instructions
• What is the Fetch istage

  The fetch stage is when the CPU fetches the next instruction from the main memory and
• What is the decode ?

  Decode is when the CPU inspects the instruction to find out what needs to be done.
• What is the execute stage


  Execute is when the CPU carries out the instruction for example:

  -Going back to the main memory and fetching data

  -performing a calculation

  -storing information back into the main memory
• Representation size


  Resolution×color depth
• Resolution


  length x width
• what is colour depth

  Number of bits per pixel
• How many bits are in a byte?

  8
• How many bytes are in a kilobyte?

  1000 bytes or 1024 bytes
• How many Kilobytes are in a Megabyte?

  1024 kilobytes or 1000 kilobytes
• How many megabytes are in a gigabyte?

  1024 megabytes or 1000 megabytes
• How many Gigabytes in a Terabyte?

  1024 gigabytes or 1000 megabytes
• What is a nibble?

  half a byte or 4 bits
• Why are Hexadecimal numbers used in Computing?

  hex codes are use in computing to simplify binary code so that humans can understand it more easily
• Define Metadata and suggest three examples

  Metadata is the data about data

  For example:

  -Name of file

  -Day it was created

  -The Size
• What is a Computer Network?

  computer networks are connections between nodes that allows communication between the nodes
• Disadvantages of Computer Networks

  - Expensive to setup due to the cost of cabling

  - Vulnerable to viruses as they spread very quickly on a network.

  - Data collisions can occur ,this slows the network down
• Advantages of Computer Networks

  - Sharing printers saves money, rather than having lots of printers attached to standalone computers.

  
  

  - Quicker to update software centrally than installing updates locally on standalone computers.

  
  

  - Network software licences are less expensive than several standalone licences.
• Describe the main types of computing networks

  PAN - only Bluetooth needs to be considered.

  
  

  LAN - know that these usually cover relatively small geographical areas and are often owned by a single person or organisation.

  
  

  WAN - know that the Internet is the biggest example of a WAN and that it normally cover a wide geographical area
• Star Topology


  A LAN topology in which all nodes are connected to a central computer.
• Bus Topology


  A LAN topology in which all nodes share a common line
• Advantages of wireless networks

  -Is cheap compared to wired networks as less money is spent on cabling

  -Allows mobility as there is no cabling

  -Easy to add new participants
• Disadvantages of wireless networks

  -Slower connection speeds than wired networks as it can interfered with walls and objects

  -Bad Security as connections can be easily interfered by hackers

  -Less stable as is can be easily interfered by other signals from other networks
• Bus network Advantages


  -Uses less cable so quite cheap to set up

  -Not dependent on a central server/switch
• Star network advantages


  Consistent performance even when the data traffic load is heavy

  IF one cable fails it will not effect any of the other devices connected to the network
• Bus disadvantages


  -if the main cable fails the whole network will fail

  -Lower security as every computer can see all data being transmitted

  -Performance slow down quickly if there is a lot traffic due to their being a shared bus cable
• Star Disadvantages


  requires extra hardware such as central switch and cabling

  if the central server/switch fails the entire network goes down