Key term
CCEA AS-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
Data, Information and Data Representation
- 12 subtopics
- 36 things to know
- AS Unit 2
What Data, Information and Data Representation covers
Data, Information and Data Representation is examined in Unit AS 2, Fundamentals of Digital Technology. It covers bits, bytes and units of storage, how many values a given number of bits can hold, converting decimal to binary, converting binary to decimal, two's complement and negative numbers, character sets: ASCII and Unicode, data, information and knowledge, factors affecting the quality of information, validation: range, type, length and presence checks, validation: format checks and lookup checks, check digits and the Modulus 11 method and batch totals, verification and the limits of checking.
The 12 subtopics
Each one has its own page. CCEA AS Digital Technology students sit this topic in the first year.
- Bits, bytes and units of storageThe bit and the byte, the nibble, and the kilobyte, megabyte, gigabyte and terabyte as successive multiples of 1,024, together with the decimal figures manufacturers quote and why the two disagree.Open →
- How many values a given number of bits can holdWhy 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.Open →
- Converting decimal to binaryDecimal, denary and base 10 as the same system, the place values of an eight-bit number, and worked conversions from decimal into binary by repeated subtraction of place values.Open →
- Converting binary to decimalReading the place values of an eight-bit pattern and adding those that are set, with worked conversions, the effect of adding a 0 to the right, and checking an answer by converting it back.Open →
- Two's complement and negative numbersWhy a sign bit alone is not enough, forming a negative value by inverting and adding one, reading a negative pattern back, the range from −128 to 127, and adding a negative to a positive.Open →
- Character sets: ASCII and UnicodeCharacter set, extended ASCII and how Unicode remains compatible with ASCII.Open →
- Data, information and knowledgeTerm data, term information and term knowledge.Open →
- Factors affecting the quality of informationSix factors that affect the quality of information, accuracy of information and relevance of information.Open →
- Validation: range, type, length and presence checksData validation, range check and type check.Open →
- Validation: format checks and lookup checksFormat check, lookup check and risk of making validation rules too strict.Open →
- Check digits and the Modulus 11 methodWhat a check digit protects against, weighting the digits and taking the remainder to eleven, writing ten as X, and testing a code for validity including a transposed pair.Open →
- Batch totals, verification and the limits of checkingBatch total, control total and hash total.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What do the terms decimal, denary and base 10 all refer to?
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Explain how Unicode remains compatible with ASCII.
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A supermarket till records every item scanned. Explain how that data becomes information and then knowledge.
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How can the reliability of a figure found online be judged?
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Why are several validation checks usually applied to a single field?
Numbers
Modulus 11 is applied to the code 1236. Show that the check digit is X.
Key term
The valid code 12343 is mis-keyed as 21343. Show that the Modulus 11 test detects the error.
Numbers
How many different values can be represented with 1 bit?
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Describe how to convert an 8-bit binary number to denary.
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Why is a special system needed to hold negative numbers in binary?
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Define data validation.
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Distinguish between a hash total and a control total.
Numbers
How many bits make one byte?
Numbers
How many different values can be represented with 2 bits?
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Which eight place values make up an 8-bit binary number?
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Convert 10110101 to denary.
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In an 8-bit two's complement number, what does the leftmost bit tell you?
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What do the letters ASCII stand for?
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Define the term data.
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Name six factors that affect the quality of information.
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Why can validation not guarantee that data is correct?
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What is a format check?
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Give a form of batch total that is not a sum of values.
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What is a nibble?
Numbers
How many different values can be represented with 3 bits?
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What is 45 as an 8-bit binary number?
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What is 01011010 in denary?
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What range of values can 8-bit two's complement represent?
Numbers
How many bits does the original ASCII code use, and how many characters does it define?
Key term
Define the term information.
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What is meant by the accuracy of information?
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What is a range check?
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Which pattern would a format check apply to a date entered as day, month and year?
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What is the purpose of a check digit?
Key term
Describe the double entry method of verification.
Take Data, Information and Data Representation further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Data vs Information
Data: a raw recorded fact with nothing to say what it refers to. Information: that same fact processed and placed in a context that gives it meaning.
Bit vs Byte
Bit: a single binary digit holding 0 or 1. Byte: a group of eight of them, enough for one character.
Validation vs Verification
Validation: an automatic test that an entry obeys the rules set for its field. Verification: a comparison confirming the entry matches the document it was copied from.
Questions from this topic
Each one with the model answer underneath.
- 1
What is a bit?
Model answer
A bit is a binary digit, the smallest unit of data a computer can hold, and it takes the value 0 or the value 1.
- 2
Why do computers store all data as bits?
Model answer
The electronic components of a computer have two states that can be told apart reliably, on and off, so representing every value as a pattern of two symbols keeps the circuitry simple and the storage dependable.
- 3
How many bits make one byte?
Model answer
One byte is made up of 8 bits.
- 4
What is a nibble?
Model answer
A nibble is a group of 4 bits, or half of one byte.
- 5
How many bytes are there in one kilobyte?
Model answer
One kilobyte is 1,024 bytes.
- 6
Why is a kilobyte counted as 1,024 bytes rather than 1,000?
Model answer
Memory is addressed in binary, so the convenient round figure is a power of two, and 1,024 is the result of multiplying two by itself ten times.
What is inside Levo
Six ways to work the same material.
Data, Information and Data Representation revision questions
- Is Data, Information and Data Representation examined at AS in CCEA Digital Technology?
- Yes. It sits in AS Unit 2, which you take in the first year, so it is on the AS paper as well as counting towards the full A level.
- What does Data, Information and Data Representation cover in CCEA AS-Level Digital Technology?
- 12 subtopics: bits, bytes and units of storage, how many values a given number of bits can hold, converting decimal to binary, converting binary to decimal, two's complement and negative numbers, character sets: ascii and unicode, data, information and knowledge, factors affecting the quality of information, validation: range, type, length and presence checks, validation: format checks and lookup checks, check digits and the modulus 11 method and batch totals, verification and the limits of checking. Each one has its own page with questions and model answers.
- How is Data, Information and Data Representation organised?
- By the CCEA 2650 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Data, Information and Data Representation, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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