Flashcards
y11 revision notes
Cards in this deck (94)
- 1Representation of numbersbinary (computers), denary, hexadecimal(humans)
- 2character storageASCII - 7 or 8 bits, limited 128 or 256 characters
Unicode - 16 bits, represent more characters than ASCII, more memory hungry - 3graphicsBitmap > grid of pixels, resolution dependant on amount of pixels, higher resolution means more detail but more storage needed,
size of image = bpp x w x h - 4cont.vector > shapes and attributes stored e.g. circle as radius & position on page etc., useful for maps and shapes etc., cannot be used to store anything not made of geometric shapes
- 5SoundSound sampling> audio waveform is sampled by measuring the amplitude at fixed intervals, more samples per second (higher sample rate) or more bits per sample (higher sample resolution) results in higher quality sound, but higher memory and storage requirements
- 6bit rate & size of samplebit rate = sample rate x sample resolution
sample size = bit rate x length of sound - 7storagebit, byte, kilobyte, megabyte, gigabyte, terabyte, petabyte, exabyte, zettabyte, yottabyte
- 8Compressionsaves storage space and memory - uses complex algorithms to store the same data using fewer bytes of data - compression ratio of a file is the ratio of the uncompressed file size to the compressed file size
- 9Lossless compressiondata is compressed using algorithms that DONT ALTER CONTENT, can be restored, used for text, applications or other data that must be preserved
- 10Lossy compressionslight alternations are made to data, so cannot be restored (some data lost), higher compression rate, JPEG compression, for images, video etc.
- 11--
- 12CPU-
- 13registerssmall storage areas for use during execution of an instruction
- 14Program counterstores the address of the next instruction to be fetched
- 15Current Instruction Registerstores the instruction currently being executed
- 16Accumulatorstores values currently being processed
- 17Memory Address Registerstores the address to be read/ written in main memory
- 18Memory Data Registerstores the data to bed read/ written to main memory
- 19Arithmetic Logic unitperforms mathematical and logical operations
- 20Control unit/ clockdecodes the program instruction in the current instruction register, selects machine resources and operations, and coordinates activation of those operations
- 21Input and Output devicesallow the user to interface with the CPU e.g. keyboard, monitor
- 22Fetch Execute Cycle1. memory address in the PC copied to Memory Address Register
2. Instruction stored in Memory data register
3. Instruction in MDR copied to Current Instruction Register
4. PC is incremented ready for next instruction
5. instruction in CIR decoded and executed by the clock, potentially making use of the Arithmetic logic unit - 23CPU speedfactors
- 24Clock speed-the faster the clock speed, the more instructions can be fetched and executed in a second
- more power needed = more heat
- excessive heat can cause damage
- measured in GHz - 25Number of cores- a core is a complete processing unit
- having multiple cores allows several instructions to be fetched and executed at the same time
- results in faster CPU but is limited by ordered instructions
- increase cost of manufacturing - 26Cache size- Cache memory is extremely fast memory, used to store frequently used instructions and data
- more cache memory means instructions can be performed quicker as it is not using slow RAM - 27Additional components-
- 28Graphics Processing unitCPU that specialises in operations like vector calculations and image manipulation, allowing advanced graphical capabilities
- 29sound cardmanipulates audio - contains circuitry to sample audio waveforms into binary, and convert that binary back to an audio waveform for playing through speakers
- 30motherboardconnects all the components a computer uses
- 31Primary Storagefaster and smaller than secondary storage , directly accessible by CPU , fetches instructions
- 32RAMstore data currently in use - fast but volatile
- 33ROMcan only be read, not changed
used for e.g. computer boot up - 34Flash memorynon- volatile, can be charged
- 35cache memorysmall & extremely fast - used to store frequently used instructions and data - speed up execution
- 36virtual memorymemory management technique - switches primary storage data to slower secondary storage device when not in use
- 37Secondary storageslower than main memory but is large and used for long-term storage
- 38Magnetic hard diskstores data on spinning magnetic disk - higher capacity - slower - cheap - fragile due to moving parts - suitable for main storage on non-portable device
- 39Magnetic Tapelong strip of magnetic material - very high capacity - v cheap - data can only be read sequentially - suitable for backups
- 40Solid state drivememory chip - fast - durable - portable (small) - expensive but getting cheaper
- 41optical disk (CD DVD etc.)spinning reflective disk - v cheap & portable - slower - requires reader
- 42Cloud storageremote server on internet - highly secure and durable - portable - expensive
- 43--
- 44Logical operationsAND 1 and 1 = 1, rest = 0
OR 1 and 0 = 1 , 1 and 1 = 1
NOT 1=0 , 0=1
XOR 1 and 0 = 1, 1 and 1 = 0 - 45--
- 46Levels of computer language-
- 47High level language-designed to resemble natural language -easier for people to read and understand -likely to be fewer errors -perform complex instructions through commands -cannot be executed directly by CPU, require translation - large, complex applications where speed is not critical
- 48Low level language-uses instruction set of CPU -does not resemble natural language -hard to read and understand -hard to find errors -executed directly by CPU > efficient - speed or memory usage critical
- 49Assemblerstranslate assembly language to machine code
- 50Compliers and Interpreterstranslate high level code to machine code
- 51compilersall at once translation - released without releasing source code - fast to execute - executed only on compatible computers
- 52interpretersinterpret one line at a time - source code distributed and executed by user - slower execution - will run on any computer - easier to find runtime errors
- 53Syntax Erroroccurs when text is invalid code
- 54Runtime Erroroccurs when program tries to perform an impossible operation
- 55Logical ErrorProgram executes and exits with no errors but the program has not done what was expected - hard to detect and fix
- 56Linking ErrorOccurs when a program tries to import a function from a file that doesnt exist
- 57Rounding ErrorOccurs when values are rounded so lose accuracy
- 58Truncation ErrorOccurs when data must be shortened to fit - missing/ inaccurate parts
- 59Stages of compilation-
- 60Lexical AnalysisComments and unneeded spaces removed - keywords etc. replaced by tokens
- 61Symbol Table ContructionA symbol table is created which holds the addresses of variables, labels and subroutines
- 62Semantic AnalysisVariables checked to ensure they have been properly declared and used and are correct data type
Operations checked to ensure that they are legal for the type of variable being used - 63Code generationmachine code is generated
- 64code optimisationmake code more efficient/ faster/ less resource intensive
- 65Software toolsjust gonna give a few examples cbb to do all
- 66linkerlinks files and import functions
- 67debuggersteps through line by line
- 68break pointspause in debugging
- 69variable watchwatch the variables in real time as the program runs/ debugging
- 70Operating Systemssoftware that interfaces with the hardware of a computer and provides common services for other software
- 71Utility Softwarefew eggsamples > antivirus, clipboard manager, system profiles, backup software
- 72--
- 73networksa group of computers connected so they can communicate
- 74topologiesstar, mesh, bus & ring
- 75packet switchinggrouping data into fixed variable length packets to be sent across a network - source address (IP) destination address (IP) packet number (resembling data) data itself other tracking information & checksum (has it been corrupted)
- 76Hardware-
- 77switchanalyses each packet and sends it to the appropriate device
- 78hubcopies each packet to every device on the network
- 79routerstores addresses of devices on the network and transfers data to and from other networks
- 80gatewayjoins 2 networks that use the same base protocol
- 81bridgejoins 2 networks that use different base protocols
- 82wireless access pointallows other WIFI devices to connect to a network
- 83Network Interface Cardallows a device to connect to a network
- 84Protocolsthe set of rules governing how communication takes place - both computers must use the same protocol for communication to be successful
e.g. ethernet - protocol for wired communication - 85InternetDNS: domain name system - resolves domain names to IP addresses
URL: used to identify a particular file on a web server
scheme://subdomain.secondleveldomain.topleveldomain/subdirectory - 86OSI 7-layer model1 - Physical - transmission and reception of raw bit streams over physical medium e.g. ethernet
3 - network - structuring and managing a multi-node network including addressing, routing and traffic control e.g. IP - 87cont.7 - application - high level APIs including resource sharing remote file access e.g. HTTP
- 88Cybersecurityfew threats few defences
- 89Social Engineeringpsychological manipulation of people into revealing personal or confidential information
- 90Brute forcerepeatedly trying different combinations to try and access a system
- 91SQL injectionExploits poor security by adding SQL statements into data entry fields that destroy or copy data
- 92Penetration testingattempting to penetrate a systems security layers to demonstrate security risks
- 93firewallsnetwork security system that monitors incoming and outgoing traffic based on pre-determined rules
- 94two-factor authenticationprevents access unless 2 or more pieces of evidence are successfully given to the system
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- GCSE Computing Flashcards on y11 revision notes, created by Rebecca Hall on 06/01/2022.
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- Rebecca Hall
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