Key term
CCEA A-Level Software Systems Development CL4
Software and the Development Environment
Topic overviewSystems software and application softwareThe operating system and file managementSource code filesBinary, object and executable filesCompilers, interpreters and the build processXML files and structured dataUtility software and managing files on diskThe integrated development environmentObject oriented development platformsOpen source software and licensing
Defining Data: Types, Variables and Classes
Topic overviewPrimitive types and their storageReference types, objects and nullDeclaring variables, scope and lifetimeType casting and conversionArithmetic operators and expressionsRelational and logical operatorsOperator precedence and evaluation orderObjects as occurrences of a classAbstract, base and inherited classesAttributes and the properties of a classStatic variables in a classInterfaces and class reusability
Program Control Structures
Topic overviewSequence and the order of executionMethods and passing control between themSelection with IF and IF ELSENested IF and multi-way selectionThe switch statementCount-controlled repetition with FORConditional repetition with WHILE and DO WHILENested loops and tracing iterationsBreaking out of loops and avoiding infinite loopsChoosing and evaluating control structures
Objects, Classes and Data Structures
Topic overviewConstructors and creating objectsMethods, parameters and return valuesEncapsulation and access modifiersGetters, setters and validating an object's stateInheritance and the base classOverriding methods and run-time polymorphismOverloading methodsChoosing and organising data structuresStrings and string handlingStatic arrays of simple typesArrays of objects
Exception Handling and Managing Input and Output
Topic overviewWhy errors have to be trappedTypes of error and how an exception is raisedThe try and catch blockCatching more than one kind of exceptionThe finally block and releasing resourcesThrowing exceptions and writing an exception classChecked and unchecked exceptionsReading and validating input from the command lineControlling screen outputText filesBinary filesObject files and serialisation
Testing an Object Oriented Application
Topic overviewWhy an object oriented application must be testedChoosing test data: normal, boundary and erroneousWriting a test plan for a classTesting a class method by methodTesting constructors and object stateTesting inheritance and overridden methodsTesting error handling pathsDry runs and trace tablesTest harnesses, drivers and stubsRecording and interpreting test resultsEvaluating a test plan and re-testing
Graphical User Interface Objects and Events
Topic overviewGraphical user interfaces and console programsForms and their common propertiesLabels, text boxes and text areasButtons, check boxes and radio buttonsLists, combo boxes and other selection controlsProperties, methods and events of a GUI objectContainers, panels and laying out a formThe event loop and the event queueEvent handlers and registering a listenerThe event object and reading it inside a handlerButton, mouse and keyboard triggers
Multiple Forms and Linking to Files
Topic overviewWhy an application needs more than one formCreating, showing, hiding and closing a formModal and modeless formsPassing data between formsMenus, menu items and shortcutsToolbars and navigation buttonsDesigning navigation for a multi form applicationReading and writing text filesBinary files and streamsObject serialisation and object filesChoosing between text, binary and object files
Designing, Testing and Evaluating an Event Driven Application
Topic overviewStoryboards and what they showBuilding a storyboard from user requirementsPrototyping and refining a designError trapping in an event driven applicationUsing try and catch inside an event handlerValidating what a user types into a controlDesigning a test strategy for an event driven applicationTest plans and choosing test dataTesting the paths a user takes through an interfaceDocumenting and interpreting test resultsEvaluating an application against its requirementsEvaluating features, functionality and usability
Reasons for Systems Development and Systems Methodologies
Topic overviewWhy organisations initiate systems developmentAnalysis and design principles for business solutionsRoles in development and the place of the userThe purpose of a methodology and how methodologies evolvedThe waterfall modelIterative, incremental and spiral developmentRapid application developmentThe dynamic systems development methodScrumExtreme programmingPrototyping in the development processUML modelling and simple diagrams
Managing Projects
Topic overviewThe purpose of project managementProject management concepts and the project life cycleRoles and responsibilities in project managementResources needed to develop a projectEstimating effort, duration and costGantt charts and the scheduleMilestones and checkpointsNetwork diagrams and PERTFinding the critical pathFloat and how it is usedMonitoring and controlling progressManaging risk and change
Testing Strategies
Topic overviewWhy testing matters throughout the development cycleTesting at the design stageProgram and unit testingIntegration testingSystem testingWhite box testingBlack box testingNormal, boundary and erroneous test dataUser acceptance, alpha and beta testingThe personnel involved in testingWhat a test plan containsBuilding a test plan for a scenario
Database Concepts and Entity Relationship Modelling
Topic overviewWhat a database is and why one is usedDatabase terminology: fields, records and keysThe relational modelThe hierarchical modelThe network modelEntities and attributes in an ER modelRelationships and their degreeBuilding an ER model for a problemFrom ER model to a working designComparing the three database models
Normalisation and Structured Query Language
Topic overviewWhy data is normalisedUn-normalised data and repeating groupsFirst normal formSecond normal formThird normal formWorking a full normalisation throughThe advantages and limits of normalisationThe principles of SQLSQL commands for defining and changing dataSQL statements for retrieving dataJoining tables and grouping results
Project Management and the Systems Approach in Practice
Topic overviewBreaking a development into tasks and deliverablesEstimating durations, effort and dependenciesDocumenting the plan as a Gantt chartWorking out the critical path and floatMilestones, reviews and user sign-off pointsPlanning people, resources and skillsBuilding a plan capable of reflecting changeRecording progress against the planUpdating the plan to reflect slippageRecording change requests and versions of the planEvaluating different approaches to a business problemSelecting and justifying a specific approach
Defining Requirements and Documenting the Design
Topic overviewEliciting requirements from the userWriting functional requirementsWriting non-functional requirementsSpecifying the software and hardware the solution needsProducing and agreeing the user requirements specificationDesigning the data model and the tablesDesigning the inputs, the screens and the navigationDesigning the outputs and the reportsDocumenting the processes and the logic of the solutionTesting the design against the desired user outcomesPresenting the design and the solution using appropriate media
Building a Desktop Solution with a Database
Topic overviewApplying relational techniques to a real solutionChoosing the database and the development toolConnecting the application to the databaseData adaptorsData setsData commands and parameterised queriesBinding the database to the interfaceMultiple forms and navigationSaving changes and protecting the dataTesting and documenting the built solution
Testing and Evaluating the Solution
Topic overviewPlanning the testing of the finished solutionChoosing test data: normal, boundary and erroneousTesting validation and error handlingTesting the database and its queriesTesting the user interface and the navigationTesting the whole solution and testing with the userDocumenting test outcomes as evidenceDiagnosing failures and retestingEvaluating the test proceduresEvaluating the solution against the user requirementsEvaluating delivery against the project planEvaluating your own performance on the development
Project Management and the Systems Approach in Practice
Working out the critical path and float
- 3 things to know
- A2 Unit 2
Overview
Finding the longest chain of dependent tasks, what total float and free float each mean, why a task on the critical path has none, and what happens when a task overruns its float.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
A plan has two chains between the same two points, one of 20 days and one of 14 days. Which chain is critical?
Key term
What does it mean to say a task has zero float?
Questions from this subtopic
Each one with the model answer underneath.
- 1
How is the critical path through a project plan identified?
Model answer
The critical path is the longest chain of dependent tasks through the plan. Its length sets the earliest possible finish date.
- 2
A plan has two chains between the same two points, one of 20 days and one of 14 days. Which chain is critical?
Model answer
The chain of 20 days is critical, because the development cannot finish before its longest chain of dependent work is complete.
- 3
A critical chain runs for 20 days and a parallel chain between the same points runs for 14 days. How much float has the shorter chain?
Model answer
The shorter chain has six days of float, because 20 days minus 14 days leaves six spare days.
- 4
What does it mean to say a task has zero float?
Model answer
A task with zero float cannot slip by even one day without delaying the finish of the whole development.
- 5
Why does the developer watch the tasks on the critical path most closely?
Model answer
Delay to a critical task delays the delivery date, while delay elsewhere may be absorbed by the float on that task.
- 6
What happens to the critical path when a task overruns more than its float?
Model answer
The overrunning task becomes critical, and the critical path shifts onto the chain that contains it.
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