Key term
WJEC A-Level Computer Science 601-5345-3
Hardware: Architecture, Memory and Storage
Networks and Data Transmission
Logic Gates and Boolean Algebra
Data Representation and Data Types
Data Structures
Organisation of Data: Files and Records
Database Systems
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Principles of Programming
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Software Engineering and Program Construction
Topic overviewIntegrated development environments and their purposeEditors, syntax highlighting and code entry toolsDebugging tools: breakpoints, stepping and watchesTranslation, source code and object codeLexical analysis and the symbol tableSyntax and semantic analysisCode generation and optimisation
Types of Software System
Practical Programming
Data Security and Integrity
Computing, Society and the Law
Topic overviewSocial and economic change from computingComputers and the nature of employmentThe digital divide and cultural changeEnvironmental cost of computingData protection and freedom of information lawThe Computer Misuse Act 1990 and computer crimeCopyright, surveillance and professional codes
Advanced Data Structures and Logic
Recursion, Sorting and Searching
Programming Paradigms and Translators
Topic overviewFunctional, declarative and imperative paradigmsClasses, methods and object-oriented designStandardisation of computer languagesAmbiguity in natural language and unambiguous notationBackus-Naur form and syntax diagramsCompilers, interpreters and assemblersTranslation and execution errors
System Design and Human-Computer Interaction
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Topic overviewSoftware tools for the software engineering processSoftware packages in systems analysis and specificationSoftware packages in systems designTesting tools and testing strategiesProgram version managementProgram libraries and project management toolsCodes of conduct and professional behaviour
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Number Representation and Floating Point
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Topic overviewConsistency, redundancy and data independenceRelational organisation and normalisationRestructuring data into third normal formEntity relationship modellingQuery languages and SQLValidation, verification and the DBMSBig Data, data warehousing and miningDistributed systems and distributed databases
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Data Representation and Data Types
The binary number system
- 3 things to know
- AS Unit 1
Overview
Column values in an eight-bit binary number, largest value eight bits can hold as an unsigned number and largest unsigned value that fits in sixteen bits.
What you need to know
Answer each one before you reveal it.
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Key term
What are the column values in an eight-bit binary number?
Key term
Convert 10110110 in binary to denary.
Questions from this subtopic
Each one with the model answer underneath.
- 1
What are the column values in an eight-bit binary number?
Model answer
Reading from the right they are 1, 2, 4, 8, 16, 32, 64 and 128, that is 2⁰ up to 2⁷, each double the one to its right.
- 2
Convert 10110110 in binary to denary.
Model answer
The set columns are 128, 32, 16, 4 and 2, which add to 182.
- 3
Convert 200 in denary to eight-bit binary.
Model answer
Taking 128, then 64, then 8 accounts for the whole value, giving 11001000.
- 4
Convert 45 in denary to eight-bit binary.
Model answer
The columns 32, 8, 4 and 1 add to 45, giving 00101101.
- 5
Convert 00111111 in binary to denary.
Model answer
The set columns are 32, 16, 8, 4, 2 and 1, which add to 63.
- 6
What is the largest value eight bits can hold as an unsigned number, and why?
Model answer
It is 11111111 in binary, which is 255 in denary, because eight bits give 2⁸ = 256 patterns and the counting starts at zero.
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