Numbers
CCEA A-Level Digital Technology 2650
Systems Analysis and Development Approaches
Topic overviewThe software crisis and the need for systems developmentUser needs, time and costRoles in a systems development teamThe purpose of analysisFact-finding techniquesFunctional and non-functional requirementsData flow diagramsThe waterfall modelRapid application development and AgileResources, constraints and risks in a software projectProject management, Gantt charts and critical path analysisVersion management
Design, Development and Testing
Topic overviewThe purpose of systems designStoryboarding the user interfacePrototyping the interface and the data modelThe development stage: turning a design into working codeWhy testing runs throughout developmentLevels of testing: unit and integrationSystem testingAcceptance testingAlpha and beta testingThe purpose and components of a test planTypes of test data
Implementation and System Security
Topic overviewThe purpose of system implementationDirect and parallel changeoverPilot and phased changeoverUser documentationTechnical documentationData conversionThe purpose of system maintenanceCorrective, adaptive and perfective maintenanceArchiving dataBackup and recoveryFull, differential and incremental backupsDisaster recovery plans
Programming
Topic overviewThe purpose of a computer programThe integrated development environmentTranslation: compilers, interpreters and assemblersThe stages of compilation and linkingAlgorithms, pseudocode and syntaxVariables, constants and data typesSequence and selectionIteration: count-controlled and condition-controlled loopsFlowcharts and algorithm representationObjects, classes and methodsInheritance and evaluating the object-oriented approach
Data, Information and Data Representation
Topic overviewBits, bytes and units of storageHow many values a given number of bits can holdConverting decimal to binaryConverting binary to decimalTwo's complement and negative numbersCharacter sets: ASCII and UnicodeData, information and knowledgeFactors affecting the quality of informationValidation: range, type, length and presence checksValidation: format checks and lookup checksCheck digits and the Modulus 11 methodBatch totals, verification and the limits of checking
Computer Architecture and Processing Systems
Topic overviewThe processor, the clock and the registersThe fetch-execute cycleBuses, input and output controllers and portsMain memory: RAM, ROM and addressingCache memory and the memory hierarchyFactors that affect processing speedThe need for secondary storageMagnetic, optical and flash storage mediaChoosing secondary storage for common applicationsBatch, real-time and transaction processingAutomatic teller machines and point of sale terminalsSmartphones: input, output and processing
System Software, Application Software and the User Interface
Topic overviewUser interfaces: WIMP, command line and forms dialogueChoosing and evaluating a user interfaceInputting text, sound and videoThe purpose of an operating systemHow an operating system manages memory and processesTypes of operating systemUtility programsThe need for data compression, lossless and lossyZipping and archive filesCommon data file formatsApplication software: generic and special purposeObtaining and delivering software
Web Technology and Multimedia
Topic overviewThe internet, the World Wide Web and web standardsURLs, HTTP and the request-response cycleDomain names, DNS and IP addressesWeb browsers, search engines, cache and cookiesWeb servers, hosting, ISPs and file transferIntranets and how an organisation uses oneCreating web pages with HTMLHTML tags for text, lists, images and linksStyling pages with CSSMultimedia assets in a web pageClient-side and server-side processingSecurity over the internet: encryption, HTTPS and certificates
Networks
Topic overviewNetwork scope: LAN, MAN and WANNetwork hardware and connection devicesIP addresses and MAC addressesPeer-to-peer and server-based networksBus, star and ring topologiesThe need for communication protocolsThe OSI seven-layer modelTCP/IP, Ethernet and media access methodsWi-Fi, Bluetooth, VoIP and RFIDBandwidth and broadbandTransmission media: metal cable, fibre optic and wirelessDetecting and correcting transmission errors
Databases
Topic overviewThe relational database and its main featuresLogical and physical data modelsEntities, attributes and keysEntity-relationship modellingNormalisation to third normal formThe data dictionaryStructured Query Language: creating and changing dataStructured Query Language: retrieving dataQuery By Example and alternatives to SQLDatabase security, integrity and recovery
Artificial Intelligence, Expert Systems and Robotics
Topic overviewWhat artificial intelligence meansThe Turing test and machine intelligenceNeural network modellingThe structure of an expert systemThe knowledge base and the inference engineShells, heuristics, fuzzy logic and the knowledge engineerExpert systems in medicine, fault diagnosis and insuranceNatural language processingVoice recognition technologyEvaluating natural language and voice recognition systemsThe technology of roboticsRobotics in commercial situations
Mobile Technology, Data Mining and Cloud Computing
Topic overviewCells, masts and frequency reuseHandoff between cellsThe base station controller, the mobile switching centre and the PSTNWhat data mining isGathering and storing data for miningProcessing and analysing large volumes of dataBig data in health, finance and retailData mining and the privacy of the individualWhat cloud computing isVirtualisation, hosted instances, hosted solutions and clusteringCloud services: storage, email, software and backupEvaluating cloud computing for business
Individual, Social and Legal Considerations
Topic overviewThe Data Protection Act 2018 and the UK GDPRThe data protection principles and the rights of the data subjectThe Copyright, Designs and Patents Act 1988The Computer Misuse Act 1990Data protection duties of an organisationHow the legislation affects employees and the publicThe ethics of automated decision makingOnline censorshipMonitoring of personal behaviourThe ethics of artificial intelligence and of personal information
The Development Project: Analysis and Design
Topic overviewScheduling the project with a Gantt chartInternal and external constraints on the solutionDetailing user requirements as inputs, processes and outputsPrioritising requirements as essential and non-essentialData flow diagrams at level 0 and level 1Specifying hardware and software requirementsThe overall system designProcess descriptions and algorithmsUser interface design and validationData modelling and normalisation for the solutionDesigning the queries and reportsDeveloping a comprehensive test plan
The Development Project: Build, Testing and Evaluation
Topic overviewChoosing software to develop the solutionBuilding the solutionTest data and the types of testingCarrying out and recording the testingDocumenting a strategy for system implementationEvaluating the solution against the user requirementsIdentifying extensions to the systemThe electronic user guideBringing the system into use and supporting itDocumentation for the completed system
Data, Information and Data Representation
How many values a given number of bits can hold
- 3 things to know
- AS Unit 2
Overview
Why n bits give two to the power of n patterns, working out how many bits a given number of categories needs, and the range a fixed number of bits can represent.
What you need to know
Answer each one before you reveal it.
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Numbers
How many different values can be represented with 2 bits?
Numbers
How many different values can be represented with 3 bits?
Questions from this subtopic
Each one with the model answer underneath.
- 1
How many different values can be represented with 1 bit?
Model answer
One bit can represent 2 different values, 0 and 1.
- 2
How many different values can be represented with 2 bits?
Model answer
Two bits can represent 4 different values, written as 00, 01, 10 and 11.
- 3
How many different values can be represented with 3 bits?
Model answer
Three bits can represent 8 different values.
- 4
State the rule linking the number of bits to the number of values that can be represented.
Model answer
The number of different values is 2 raised to the power of the number of bits, so n bits give the result of multiplying two by itself n times.
- 5
How many different values can be represented with 8 bits?
Model answer
Eight bits can represent 256 different values.
- 6
If 8 bits are used for positive whole numbers starting at zero, what is the largest value that can be held?
Model answer
The largest value is 255, because the 256 available patterns run from 0 up to 255.
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