Key term
Eduqas A-Level Computer Science A500QS
Data Structures: Arrays, Records and Hash Tables
Stacks, Queues, Linked Lists and Trees
Boolean Logic and Simplification
Algorithms, Pseudo-Code and Programming Constructs
Variables, Scope, Parameters and Identifiers
Recursion and Modular Programming
Sorting Algorithms
Searching and Shortest-Path Algorithms
Big O Notation and Algorithm Efficiency
Validation, Verification and Testing
Data Compression
Programming Paradigms and Computer Languages
Topic overviewProgramming paradigms and where each is usedProcedural programmingEvent-driven and visual programmingMark-up languagesObject-oriented programming: objects, classes and methodsAmbiguity in natural language and the standardisation of languagesBackus-Naur form and syntax diagramsHigh-level and low-level languages, and choosing one
Systems Analysis, Maintenance and Documentation
Topic overviewWaterfall, Agile and approaches to systems developmentThe feasibility study, budgets and time scalesMethods of investigationAbstraction, decomposition and data flow diagramsSelecting suitable hardware and softwareAcceptance testing and methods of changeoverPerfective, adaptive and corrective maintenanceBackup and recovery proceduresUser and maintenance documentation
System Design and Human-Computer Interaction
Software Engineering Tools and Translators
Topic overviewSoftware tools for the software engineering processSoftware packages in analysis, specification, design and testingIntegrated development environmentsDebugging toolsProgram version managementCompilers, interpreters and assemblersThe stages of compilationTranslation errors and execution errors
Computing, Society and the Law
Computer Architecture, the Processor and Assembly Language
Topic overviewHardware elements and how they are connectedVon Neumann architecture and the stored program conceptThe processor: control unit, ALU and registersTypes of memory: RAM, ROM and virtual memoryCache memory and locality of referenceThe fetch-execute cycle and its registersParallel processing and the limits to parallelisationAssembly language and executing a program
Input, Output and Secondary Storage
Topic overviewInput devices and how data is capturedOutput devices and how results are presentedChoosing input and output devices for a situationVoice input, dictation and voice print recognitionMagnetic, optical and solid state storageComparing secondary storage for a purposeDisc organisation, fragmentation and defragmentation
Networks, Protocols and the Internet
Topic overviewNetworks, LANs and WANsNetwork topologies and connection hardwareNetworking standards and the layered modelIP addressing, TCP and UDPApplication protocols: HTTP, FTP, SMTP, IMAP and DHCPHandshaking and establishing a connectionWireless hardware and wireless technologiesThe internet and connected mobile devices
Data Transmission and Network Performance
Topic overviewSerial and parallel transmissionSimplex, half duplex and full duplexMultiplexing and sharing a channelCircuit, message and packet switchingPackets, headers and packet contentsNetwork collisions and collision detectionRouting traffic on a networkCalculating transfer rates and lowest cost routes
Number Systems and Binary Arithmetic
Data Types, Characters and Floating Point
Topic overviewPrimitive data typesStorage requirements for each data typeASCII and standardised character setsUnicode and multilingual encodingFloating point form: mantissa and exponentConverting between real numbers and floating pointInteger and floating point comparedTruncation, rounding and accuracy
Files, Records and File Organisation
Topic overviewThe purpose of files in data processingFiles, records and fieldsFixed and variable length fields and recordsMaster files and transaction filesSerial and sequential file accessIndexed sequential access and multi-level indexesDirect access and hashing algorithmsOverflow handling and file reorganisationFile security, backups, generations and archiving
Databases, Normalisation and Entity Modelling
SQL, Big Data and Distributed Systems
Topic overviewQuery languages and the purpose of SQLCreating tables: CREATE TABLE, data types and keysRetrieving data with SELECT, FROM and WHEREComparison operators, IN, AND, OR and sub-queriesSorting, grouping and aggregate functionsInserting, updating, deleting and joining dataThe DBMS, the data dictionary and distributed databasesBig Data, data warehousing, data mining and predictive analytics
The Operating System and Its Modes
Topic overviewThe need for an operating system and the role of the kernelManaging peripherals, processes and memory protectionThe user interface and the layers between user and hardwareDirectory structures and file attributesUtility softwareBatch processing, real time control and real time transaction systemsTypes of operating system: single-user, multi-user, multi-tasking and multi-programmingDesigning an interface for different users and environments
Interrupts, Memory Management and Scheduling
Topic overviewWhat causes an interruptInterrupt handling and the interrupt service routineInterrupt priorities and how they are allocatedPartitioning main memoryMethods of data transfer between processor and devicesBuffers and double bufferingHigh level scheduling, processor and device allocationProcess states, time-slicing, polling and threading
Types of Software System
Data Security, Cryptography and Attack
Topic overviewOnline updating and the integrity of shared filesDangers of holding personal dataClerical procedures, access levels, passwords and write protectionCryptography: its purpose, and symmetric and asymmetric keysHashing, digital signatures and certificatesCaesar and Vernam ciphers and comparing cipher strengthBiometric technologies and their limitationsThreats, damage and contingency planningMalicious software, hacking and penetration testing
Variables, Scope, Parameters and Identifiers
- 7 subtopics
- 21 things to know
- Component 1
What Variables, Scope, Parameters and Identifiers covers
Variables, Scope, Parameters and Identifiers is examined in Component 1, Programming and System Development. It covers variables and constants, self-documenting identifiers, annotation and program layout, scope of variables: local and global, lifetime of variables, procedure calling, parameters and return values and call by value and call by reference.
The 7 subtopics
Each one has its own page.
- Variables and constantsVariable in a program, constant in a program and difference between a variable's identifier and its value.Open →
- Self-documenting identifiersSelf-documenting identifier, two rules most languages impose on identifier names and camel case.Open →
- Annotation and program layoutAnnotation in a program, how indentation helps a reader understand a program and three features of good program layout.Open →
- Scope of variables: local and globalScope of a variable, local variable and global variable.Open →
- Lifetime of variablesLifetime of a variable and lifetime of a global variable.Open →
- Procedure calling, parameters and return valuesTerm parameter, formal parameter and an actual parameter and return value.Open →
- Call by value and call by referenceCall by value and call by reference.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What is a parameter, and what is the difference between a formal and an actual one?
Key term
Why must a subprogram never return the address of one of its local variables?
Key term
What is a variable in a program?
Key term
What is a self-documenting identifier?
Key term
What is annotation in a program?
Key term
What is meant by the scope of a variable?
Key term
What is call by value?
Key term
What is a constant in a program?
Key term
Rewrite the identifier x2 as a self-documenting identifier for a variable holding a pupil's surname.
Key term
Give two things a useful comment should record.
Key term
Define a local variable.
Process
What happens when a procedure is called?
Key term
What is call by reference?
Key term
Give two reasons a programmer would use a named constant rather than typing the value repeatedly.
Process
Give a self-documenting identifier for a procedure that prints an end-of-year report.
Key term
Why is a comment that restates the code useless?
Key term
Define a global variable.
Key term
What is meant by the lifetime of a variable?
Key term
Define the term parameter.
Process
A variable X holds 5 and is passed by value to a procedure that doubles its parameter. What does X hold after the call?
Take Variables, Scope, Parameters and Identifiers further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Procedure vs Function
Procedure: performing a task and giving back no value. Function: giving back a single value into an expression.
Annotation vs Self-documenting identifier
Annotation: a separate comment. Self-documenting identifier: carrying the meaning in the name itself.
Questions from this topic
Each one with the model answer underneath.
- 1
What is a variable in a program?
Model answer
A variable is a named location in memory whose contents can change while the program runs. The name refers to the value currently stored there.
- 2
What is a constant in a program?
Model answer
A constant is a named value that is fixed when the program is written and cannot change while it runs.
- 3
Give two reasons a programmer would use a named constant rather than typing the value repeatedly.
Model answer
A named constant is changed in one place, so an update cannot be applied inconsistently. The name also explains what the value means to a reader.
- 4
A program prices items and adds VAT. State which quantity suits a constant and which suits a variable.
Model answer
The VAT rate suits a constant because the rate is fixed for the whole run. The item price varies from item to item and needs a variable.
- 5
What happens if a program tries to assign a new value to a constant?
Model answer
The translator reports an error and the assignment is refused. A constant may only be given its value once, at declaration.
- 6
Explain the difference between a variable's identifier and its value.
Model answer
The identifier is the name the programmer uses to refer to the store. The value is the data held in that store at a given moment.
What is inside Levo
Six ways to work the same material.
Variables, Scope, Parameters and Identifiers revision questions
- What does Variables, Scope, Parameters and Identifiers cover in Eduqas A-Level Computer Science?
- 7 subtopics: variables and constants, self-documenting identifiers, annotation and program layout, scope of variables: local and global, lifetime of variables, procedure calling, parameters and return values and call by value and call by reference. Each one has its own page with questions and model answers.
- How is Variables, Scope, Parameters and Identifiers organised?
- By the Eduqas A500QS specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Variables, Scope, Parameters and Identifiers, 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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