GCSE

• portable language


  Language that can be run on more than one type of computer.
• Which language usually has a more optimised code

  Low level
• Which systems use low level languages

  Embedded

  Lll produce shorter and faster code, which is useful for computers with low specifications
• Why do compilers hide source code from end user

  To protect the developers intellectual property
• intellectual property


  A product, such as an expressed idea or concept, that has commercial value.
• interpreter


  Converts a program written in a higher level language into a lower level language and executes it, beginning execution before converting the entire program.
• Compiler


  A program that translates instructions or code into a language that can be read and understood by a computer.
• Compiler vs. Interpreter


  Compiler: program that converts source code into machine language instructions that can be processed by the computer; the resulting program runs faster than the interpreter

  
  

  Interpreter: reads through & converts code to instructions one line at a time while it's running and sends it to the processor; if you have a code that changes frequently, it's better to use an interpreter because it has more flexibility; when you need to change a code using a compiler you have to shut the program down, implement the change, and then start
• Compiler statements


  Hide source code

  Translate everything in one go

  Produce a list of errors
• Assemblers


  Provide direct control of hardware

  Output efficient code

  Need deep technical knowledge
• Efficiency


  using resources in such a way as to maximize the production of goods and services
• time-efficient


  working well without wasting time
• system software


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

  Controls hardware to provide an environment for apps to run
• Application Software


  computer software created to allow the user to perform a specific job or task
• device driver


  A software program that provides the instructions your computer needs to communicate with a device, such as a scanner.
• Utility Software


  systems software that perform tasks related to managing the computer's resources, file management, diagnostics, and other specialized chores
• Defragmentation


  A utility that reduces the amount of fragmentation by applying an algorithm to physically organizing the contents of the hard disk to store the pieces of each file contiguously.
• Application Programming Interface (API)


  a set of routines, codes, protocols, and tools for building software applications
• OS


  Memory management - controls the allocation of RAM to each running process

  Device management - keeps track of which devices are connected to which port

  File management -manages access rights to each file
• port (computer)


  is a physical docking point using which an external device can be connected to the computer. It can also be programmatic docking point through which information flows from a program to the computer or over the Internet.
• Graphic User Interface (GUI)


  Mechanism whereby a user accesses computer functions through a trackball, touch pads, a mouse, and icons.
• Command Line Interface (CLI)

  An interface that accepts text commands at a prompt, usually for immediate execution with immediate display of output. Using the keyboard
• Why still use a low level langauge

  Greater control over a program with lower memory use

  Greater control over cpu to make program run quicker

  Maintain old code or hardware
• Why is assembly language not usually used when writing large application programs?

  Assembly language has minimal formal structure, so structure must be imposed by programmers who have varying levels of experience. This leads to difficulties maintaining existing code.
• Why is it used instead of machine code

  More readable for users so can be programmed and updated more easily and more quickly
• Unicode


  A character set that enables most of the languages of the world to be symbolized with a special character identification.
• Colour depth


  The number of bits used for each pixel
• Bitmap images


  Images created using a grid of small squares called pixels. The colour is stored as a binary value
• How to increase quality of audio

  Increase sample rate

  Increase sample size
• Sample Rate


  the number of samples taken per second
• Sample resolution


  The number of bits used to store the value of each sample. The higher the number of bits the more accurately the value is stored.
• How is audio stored digitally?

  By sampling its amplitude at regular intervals
• RLE (Run Length Encoding)


  Instead of storing the code for each individual pixel in a bitmapped image, this compression technique will store the code for just one pixel, and then the data for how many times it is repeated.
• How do image compression algorithms work

  Group adjacent pixels together to give them an average colour

  Rle program
• Is RLE lossy or lossless?

  lossless
• Is Huffman encoding lossy or lossless?

  lossless
• Huffman encoding


  Using a variable-length binary string to represent a character so that frequently used characters have short codes
• greedy algorithm


  an algorithm that makes the best choice at each step
• Left branch of Huffman

  0
• Merge Sort


  A type of divide and conquer algorithm that was incited by John von Neumann. First the list is divided into the smallest unit, then each element is compared with the adjacent one to sort and merge them. This is done until all elements are sorted and merged into one singualr list