cs: paper 2 revision

• abstraction


  removal of unnecessary detail
• decomposition


  breaks complex problem down into smaller problems
• advantage of merge sort over bubble sort

  efficient for large datasets, list doesn't need to be ordered
• why must a list need to be if binary sort is used

  it must be sorted alphabetically
• binary search process


  midpoint of dataset is found. compare whether item is higher or lower than midpoint, get rid of unused sub-set, find midpoint of used sub-set, compare again and repeat.
• variables purpose


  can change throughout the program
• programming constructs


  selection, sequence, iteration
• example and definition of a constant

  Pi, it's value stays the same
• data types:


  string, real, Boolean, integer
• SQL structure


  SELECT(info), FROM(table name), WHERE(condition is met)
• symbol for selecting all fields in a table (SQL)

  *
• calling an array using index


  [value on column down, value on row across]
• input validation

  to ensure numerical data entered is sensible/meets expectations
• range check


  to ensure value is within boundary and acceptable.
• data validation


  process of checking data is obeying rules so its sensible and expected
• authentication


  confirms identity of someone on a computer system, grants them access(username and password)
• maintainability


  indentation, comments, sensible variable names, subroutines.
• presence check


  ensure input data is entered, so the program can function normally
• logic error


  program runs but does not give expected output
• syntax error

  error in grammar which prevents program running.
• which type of testing, tests programs regularly as its written?

  iterative testing.
• which type of testing, tests a program at the end?

  terminal/final testing
• what do comments do


  explain what each part of the program is doing
• what does sensible variable name mean


  changing a variable name to something more meaningful that a single character
• what are subroutines used for

  so code can be reused in another part of the program
• logical operatiors


  AND, OR, NOT
• AND rule


  both inputs MUST be true
• OR rule


  either input can be true or false
• NOT rule

  input must be false to give true output
• high level language definition

  English-like keywords, translated into machine code to be executed(syntax)
• why does a computer translate HLL code before its executed

  HLL can't be executed directly by the CPU, it must be translated by the processor into machine code first
• compiler function


  all code translated in one go, saves as an executable file and runs anytime
• interpreter function


  translates and executes the code one line at a time, no executable file so it must be retranslated each time its run.
• why should a game be commercially compiled?

  compiling produces executable files, so users of the program can't view or modify the source code
• why is low level language used for embedded system


  LLL can be directly processed by processor, embedded systems run quickly.
• differences between high level and low level languages

  HLL: translated into machine code before run, runs on range of different computers. LLL: directly run by processor, only works with specific type of computer.
• advantages of using an interpreter during the development phase

  identifies syntax errors as each line of program is translated and run, debugging is simple and precise.
• feature of IDE: run time environment


  allows code to run within the IDE
• features of IDE: error diagnostics


  helps programmer to identify and fix errors.
• features of IDE: translator


  allows code to be translated into machine code to be executed by processor.