Numbers
AQA A-Level Computer Science 7517
Fundamentals of Programming
Topic overviewData typesProgramming concepts and program structureArithmetic operationsRelational Operations, Constants and VariablesBoolean operationsString-handling operationsRandom numbers and exception handlingSubroutines, parameters and return valuesVariable scope and stack framesRecursive techniquesProgramming paradigms and the procedural approachClasses, Objects, Inheritance and PolymorphismAggregation, Composition, Class Diagrams and Design Principles
Fundamentals of Data Structures
Fundamentals of Algorithms
Theory of Computation
Topic overviewLogic Problems and Algorithm ConstructsPseudo-Code, Hand-Tracing and Program CorrectnessRepresentational Abstraction, Generalisation and Information HidingProcedural and Functional AbstractionData Abstraction and Problem ReductionDecomposition and CompositionAutomation and Finite State MachinesSets and Set NotationSubsets and Set OperationsRegular expressions and regular languagesBackus-Naur Form and syntax diagramsComparing Algorithms and FunctionsOrder of complexity and Big-O notationLimits of computation, tractability and heuristicsComputable problems and the Halting problemTuring machines
Fundamentals of Data Representation
Topic overviewNumber systems and the sets of numbersNumber bases: decimal, binary and hexadecimalBits, bytes and units of informationUnsigned binary and binary arithmeticSigned binary using two's complementFixed point and floating point representationNormalisation of floating point numbersRounding errors, accuracy, range and precisionCharacter coding systemsError checking and correctionBit patterns, analogue and digitalBitmapped graphicsVector graphicsDigital representation of soundMIDI and Data CompressionEncryption
Fundamentals of Computer Systems
Topic overviewHardware, Software and Its ClassificationSystem Software and the Operating SystemTranslators and the Role of the Operating SystemClassification of programming languagesTypes of program translatorLogic Gates and Their Truth TablesLogic Circuits and D-Type Flip-FlopsHalf-Adders and Full AddersBoolean algebra
Fundamentals of Computer Organisation and Architecture
Topic overviewInternal components, buses and von Neumann and Harvard architecturesThe Stored Program Concept and the ProcessorThe Fetch-Execute cycleThe processor instruction setAddressing modesMachine-Code OperationsShifts, Halting and Assembly Language ProgramsInterruptsFactors affecting processor performanceInput and output devicesSecondary storage devices
Fundamentals of Communication and Networking
Topic overviewCommunication methodsCommunication basicsNetwork Topology and Types of NetworkingWireless networkingThe Internet and Packet SwitchingRouting, URLs and Domain NamesFirewalls, Worms, Trojans and VirusesEncryption, Digital Signatures and CertificatesTCP/IPStandard application layer protocolsIP Address Structure and Subnet MaskingIP Standards and Public and Private AddressesDHCP and Network Address TranslationClient server modelThin- versus thick-client computing
Consequences of Uses of Computing
Systematic Approach to Problem Solving
Fundamentals of Databases
Big Data
Fundamentals of Computer Systems
Logic Gates and Their Truth Tables
- 2 things to know
- Paper 2
Overview
Recall questions on the truth tables of the NOT, AND, OR, XOR, NAND and NOR gates.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Describe the standard distinctive-shape symbols for the OR, NOR and XOR gates.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Construct the truth table for a NOT gate.
Model answer
One input A, one output Q, where Q is the opposite of A. A = 0 gives Q = 1; A = 1 gives Q = 0. It is written Q = NOT A, or A with a bar over it.
- 2
Construct the truth table for an AND gate.
Model answer
Two inputs A and B, output Q = 1 only when both inputs are 1. A = 0, B = 0 gives Q = 0; A = 0, B = 1 gives Q = 0; A = 1, B = 0 gives Q = 0; A = 1, B = 1 gives Q = 1. It is written Q = A AND B, or A.B.
- 3
Construct the truth table for an OR gate.
Model answer
Two inputs A and B, output Q = 1 when at least one input is 1. A = 0, B = 0 gives Q = 0; A = 0, B = 1 gives Q = 1; A = 1, B = 0 gives Q = 1; A = 1, B = 1 gives Q = 1. It is written Q = A OR B, or A + B. Note that this is inclusive OR: it is 1 when both inputs are 1.
- 4
Construct the truth table for an XOR gate.
Model answer
Two inputs A and B, output Q = 1 when the inputs are different and 0 when they are the same. A = 0, B = 0 gives Q = 0; A = 0, B = 1 gives Q = 1; A = 1, B = 0 gives Q = 1; A = 1, B = 1 gives Q = 0. It is written Q = A XOR B, and is exclusive OR: one or the other, but not both.
- 5
Construct the truth table for a NAND gate.
Model answer
Two inputs A and B, output Q = 0 only when both inputs are 1; it is the inverse of AND. A = 0, B = 0 gives Q = 1; A = 0, B = 1 gives Q = 1; A = 1, B = 0 gives Q = 1; A = 1, B = 1 gives Q = 0. It is written Q = NOT (A AND B).
- 6
Construct the truth table for a NOR gate.
Model answer
Two inputs A and B, output Q = 1 only when both inputs are 0; it is the inverse of OR. A = 0, B = 0 gives Q = 1; A = 0, B = 1 gives Q = 0; A = 1, B = 0 gives Q = 0; A = 1, B = 1 gives Q = 0. It is written Q = NOT (A OR B).
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