computer science (aqa)

• Lossless Compression


  Various algorithms are used to find parts in the data that are repeated
• Ring Topology

  Fast data transfer but if one machine fails the whole network will fail.
• Bus Topology


  Easy and cheap to install but if the main cable fails the whole network will crash
• Star Topology


  Reliable and high-performing but expensive to install and if a hub/switch fails the devices will not have network connection
• CPU


  Brains of the computer. Mainly processes and uses data to perform taks
• GPU


  A chip/processor designed to boost the performance of games and graphics
• RAM


  Primary Storage device which allows data to be stored and retrieved on the machine
• Volatile Memory

  Memory which only maintains it's storage while the machine is active
• Non-Volatile Memory


  Memory which maintains it storage whether or not the machine is active
• Logic Gate


  A diagram which represents boolean logic
• Virtual Memory


  Memory that appears to be main storage although most if it is held in secondary storage
• Cache


  Memory that is easily accessed by the CPU and is very fast
• Secondary Storage


  Non-Volatile memory that is not directly accessible by the CPU
• Optical


  Data is recorded by making marks in a pattern that can be read back with the aid of light.
• Magnetic


  A mechanical device in which the media is inserted
• Solid State


  A grid of electrical cells which quickly send and receive data
• NOT gate


  A logic gate that takes in 1 input & outputs the opposite

  
• AND gate


  A logic gate that takes in 2 inputs and only outputs True if both inputs are True

  
• OR gate


  A logic gate that takes in 2 inputs and outputs True if either inputs are True

  
• Truth table


  A table which holds possible states on inputs and shows the corresponding final output of a logic diagram
• Logic Diagram


  A diagram combining multiple logic gates to show the inputs and final output of a system
• Boolean Logic


  Logic which can only produce a True or False outcome

  
• Hardware


  The physical elements of a computer system

  
• Sotware


  The logical programmed parts of a computer system that tells the hardware how to function

  
• Embedded system


  A system developed for a single, or set purpose. E.g. A washing machine, microwave, digital watch
• General Purpose System


  A computer system that can change its purpose by adding more software
• ROM


  Non Volatile. Small area of memory which holds the boot up program.

  
• Device Driver


  A program stored on the hard drive that tells the computer how to communicate with a hardware device such as a printer, mouse, or keyboard.

  
• Defragger


  System software which tidies up the physical locations of where data is saved on a storage device.
• Scheduler


  System software which establishes the order in which instructions are executed by the processor
• GUI


  A User Interface which incorporates the four elements of Windows, Icons, Menus, & Pointers

  
• System Software


  software responsible for the general operation of a computer system, including the operation of hardware, running application software, and file management

  
• Application Software


  computer software created to allow the user to perform a specific job or task. eg. Word, Excel, browsers, games

  
• Autoupdate


  A scheduled patch to software (usually system software) to ensure that it is completely up to date with the latest features.

  
• Firewall


  A security system consisting of a combination of hardware and software that limits the exposure of a computer or computer network to attack from crackers

  
• Spyware


  A computer program which is installed without permission, sometimes through a virus or sometimes as part of the installation of a program. It works by collecting information and sending it back to another source. The information collected could include the websites you have been visiting or what you have been downloading. This can be used for marketing purposes but also for fraud.

  
• Antivirus


  System software that is specifically designed to detect viruses and protect a computer and files from harm

  
• Computer Virus


  a software program capable of reproducing itself and usually capable of causing great harm to files or other programs on the same computer

  
• Computer Worm


  Self-replicating program designed to carry out some unauthorised activity on a victim's computer. This software can spread themselves from one computer to another without any assistance from victims.

  
• Trojan


  A piece of software that appears to be a legitimate application, utility, game, or screensaver that performs malicious activities surreptitiously