[9-12] Comp Sci Paper 2

• What does structure chart show

  · Identification of modules

  · Hierarchy of modules

  · Parameters/variables passed between modules

  · Module iteration/selection
• Post condition loop

  REPEAT…UNTIL
• Pseudocode to define record

  TYPE

  DECLARE...

  ENDTYPE
• Pseudocode Declare 1D array

  DECLARE : ARRAY [1:] OF
• White box testing

  Necessary to test all possible paths through the code
• Why use record

  · Allows multiple data types

  · Stored under one identifier
• Structure chart shape for selection

  Diamond
• Benefits of using text files

  · Data retained when program terminated

  · Non-volatile storage
• When use count controlled loop when number iterations is known
• Syntax Error

  · Program not obey rules/grammar of programming language

  · Program cannot run

  · Mis spelt keywords
• Logic error

  · Error in algorithm

  · Program does not run as expected (give expected output)

  · E.g. wrong arithmetic operator used
• Run Time error

  · Program performs invalid operation

  · e.g. divide by zero
• Need for & benefit of abstraction

  · Need to filter out non essential information

  · Solution simplified + easier to implement

  · System tailored to needs of user
• How element added to queue

  · Increment EoQ

  · Data stored at value pointed by EoQ
• How element removed from queue

  · Element pointed at by FoQ popped

  · FoQ incremented
• Design stage

  · Choose programming language

  · Decide data structures

  · Create testing method/plan

  · Create algorithms/flowcharts

  · Program modules split to teams
• Describe decomposition

  · Breaking down problem into smaller sub problems

  · Easier to understand + solve problem

  · Assign different parts to team

  · Concept of program modules
• Rapid Application Development (RAD)

  · Provides working model

  · Prototype at early stage for approval
• Features that make pseudocode easier to read and understand.

  · Meaningful variable names

  · Indents

  · Capitilise keywords
• Algorithm

  sequence of steps that describe how to solve a problem.
• Information in identifier table

  · Name of identifiers used

  · Data type of identifier

  · Purpose of identifier

  · Value of any constants

  · Number of elements in array/string

  · If variable local or global
• Benefits of decomposition

  · Splitting smaller problems easier understand + solve

  · Easier to test/maintain

  · Solved in separate teams with different programming expertise
• Pre condition loop

  WHILE … ENDWHILE
• Integration testing

  · Modules all tested individually

  · All combined into single sub program – tested as whole
• Type of Maintenance

  · Perfective

  · Adaptive

  · corrective
• Adaptive maintenance

  · Accommodate change in requirement/legislation

  · E.g. new HTML version available
• Corrective maintenance

  · Program not performed as expected

  · There is a bug

  · E.g. passwords are not hidden
• Purpose of structure chart

  · Module hierarchy/relationships

  · How problem broken down

  · Parameters passed between modules

  · Shows if module is procedure or function
• Waterfall up arrow meaning

  more work required at previous stage to complete current stage
• Waterfall down arrow meaning

  Result from one stage is input to next stage
• Benefits of using library routines for program development

  · Already tested – error free

  · Perform complex function that programmer cannot do

  · Readily available – speeds up development time

  · Quicker and more efficient
• Reasons to use subroutine

  · Task repeated in several places

  · Part of algorithm completes specific task

  · Program simplified

  · Maintenance easier
• Beta testing

  · Test carried out by small group of users

  · Users check software works as expected no errors

  · Users provide feedback

  · Problems identified before program solved
• Features of queue

  · Each queue element contains one piece of data

  · Front + end pointer

  · Data added at back. Removed from front

  · FIFO structure

  · May be circular
• Features of linked list

  · Node contains data + pointer to next node

  · Start pointer

  · Last node has null pointer

  · Data added/removed by manipulating pointers

  · Nodes traversed specific sequence
• Benefit of development life cycle:

  easier to manage/plan project
• Principles of Rapid Application Development (RAD)

  · Modules developed as prototypes

  · Client involved in all stages during development

  · Allows for flexible development + changes
• Benefit of RAD

  · Prototype produced

  · Client involved – tailor to their needs

  · Quicker development time

  · Easier to change requirements
• Drawbacks of RAD

  · Client keep changing mind

  · Hard to plan cost/time of project
• Reasons why adaptative maintenance used

  · Change to website requirements

  · New technologies available

  · Change in relevant legislation