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Flashcards

1.3 - Exchange Data - Flashcards

Jack Ives Computing AS level Inglês 93 flashcards

Flashcards do conjunto (93)

  1. 1HTML(Hypertext Mark-up Language)
    A standardised system for tagging text files to achieve font, colour, graphic, and hyperlink effects on web pages
  2. 2CSS(Cascading Style Sheet)
    Used to define how web content should be formatted and styled
    Easy to make site wide changes
  3. 3JavaScriptA client-side scripting language
    Makes pages dynamic and interactive
    Can be used for data validations on web forms
  4. 4CompressionThe act of decreasing a files size
    Faster download and transfer speed
  5. 5Lossy CompressionRemoves data from the original file
    Original files cannot be restored
    No noticeable loss of quality (for humans)
  6. 6Lossless CompressionInformation stored is condensed with no loss of data
  7. 7Lossy Compression ExamplesJPEG
    MPEG
  8. 8Lossless Compression ExampleGIF
  9. 9DatabaseA structured, persistent collection of data
  10. 10A database must be methodical in order to:- Make processing more efficient
    - Reduce storage requirements
    - Avoid redundancy
  11. 11EntityA thing of interest to an organisation about which data is to be held
  12. 12AttributeA property or characteristic of an entity
  13. 13Flat File DatabaseA single entity contains all data
  14. 14Relational DatabaseMultiple entities joined by common attributes
  15. 15Serial FileRecords organised one after the other
    Is possible to divide data into records
    In order to process the structure has to be the same
  16. 16Sequential FileSimilar to serial but can be alphabetical
    Makes searching easier
    Problem - Unordered -> Ordered?
  17. 17Fixed Length FieldsEach field is the same no. of bytes
    Pro's:
    - Easy to program
    - Quick to search
    - Easy to calculate file size
    Con's:
    - Wasted data
  18. 18Variable Length FieldsInsert a marker (e.g. a comma) to delineate (divide) each field
    CSV = common
    Pro:
    - No wasted space
  19. 19HashingKey fields of records can be transformed to generate disk addresses
    By taking the last 3 digits from a key
    Allows random access
  20. 20Issues with a Flat File Database- Data Redundancy (Repeated data, Wasted Storage Space)
    - Data Integrity (Problems with consistency and accuracy)
  21. 21RecordAll the data about and entity
  22. 22TransactionTo exchange something
  23. 23Master FileA permanent file, periodically updated, that serves as an authoritative source of data
  24. 24Transaction FileA collection of transaction records
  25. 25Relational DatabaseData is stored in separate tables
    Each table stores a separate entity
    Tables are linked through a relationship
  26. 26Primary KeyA field in a data file containing the information capable of uniquely identifying a record in a relation to all other records in the same data file
  27. 27Foreign KeyThe primary key of one data structure placed into a related data structure to represent a relationship, supporting navigation
  28. 28Secondary KeyAn attribute that could be used for indexing but not for a primary key
    (e.g. Postcode, DoB)
  29. 29E-R Diagram(Entity-Relationship Diagram)
    A way of representing entities and relationships in a database
  30. 30TupleAn ordered set of data consisting of data in a record
  31. 31RelationA set of tuples forming a table
  32. 32DBMS(Database Management System)
    Software that creates and maintains a database
  33. 33DBMS Jobs- Database Structure
    - Queries
    - Views
    - Individual Tables
    Outputs
  34. 34DBMS Protecting + Maintenance Duties- Organising access rights
    - Automating backups
    - Preserving referential integrity
    - Creating and maintain indexes
    - Updating the database
  35. 35Transaction Processing- A type of processing that attempts to provide a quick response to the user
    - Not time critical
    - Limited range of operations, predetermined (Bank Withdrawal)
    - Must maintain data integrity
  36. 36Data IntegrityMaintenance of a state of consistency in the data store, ensuring it is fit for purpose
  37. 37Data CorruptionOpposite of data integrity (Hardware error, Software error, Electrical glitches, Human error)
  38. 38Data DictionaryHolds metadata (data about data)
    Information on everything needed to make a database function
  39. 39User ViewAppearance + Functionality of the database
    Needs a good interface
  40. 40Logical ViewHow data is organised for processing
    Construction of tables, reports, queries and the data dictionary
  41. 41Physical ViewHow data is actually recorded in storage
    Level of organisation needs to be understood by the software so the correct data is read/written
  42. 42SQLStructured Query Language
  43. 43DDL(Data Definition Language)
    A language to define the structure and instances of a database
  44. 44DML(Data Manipulation Language)
    A language for the manipulation of data
  45. 45QBEQuery By Example
  46. 46Computer NetworkA collection of hardware components and computers (nodes) interconnected by communication channels that allow sharing of resources and information
  47. 47Advantages over a Private Network- Control over security
    - Complete control over who has access to what
    - Control over what software is provided
    - Confidence of availability
  48. 48Cost of a Private Network- Specialist staff to running + maintain security
    - Functionality lost = Potential disaster?
  49. 49Methods to minimise risk:~ Redundancy, duplicate essentials
    ~ Sensible backup regime
    ~ Failover Systems, detect abnormalities and automatically transfer operations to an alternative system
    ~ Disaster Recovery Plan
  50. 50LAN(Local Area Network)
    A computer network that interconnects computers in a limited area
    (e.g. home, library, school)
    Key features:
    - Higher data-transfer speeds than WAN
    - Smaller geographical area
    - Lack of need for leased communication lines
  51. 51WAN(Wide Area Network)
    A telecommunication network that covers a broad area (i.e. a network that links across metropolitan, regional, or national boundaries
  52. 52NIC(Network Interface Card)
    An NIC is a piece of hardware that allows data packets to travel back and forth between a computer and network
    Designed to work with a specific network standard (Ethernet)
    Each has its own MAC address
  53. 53MAC Addressing(Media Access Control Address)
    A 48 bit binary unique identifier assigned to a NIC
    First 3 octets identify a manufacture
  54. 54RoutersA device that transfers data fro one network to another by forwarding data packets to their destination by the most effective route
  55. 55EthernetA Network Standard
    A system for connecting a no. of computer systems to form a LAN, with protocols to control the passing information and t avoid simultaneous transmissions by 2 or more systems
  56. 56Bus NetworkAll devices are attached to a common backbone
    Uses terminators at each end to stop data being reflected back (Decreases the risk of data collision)
  57. 57Ring NetworkAll data sent in one direction around a ring
    Each computer is connected to exactly 2 other computers
  58. 58Star NetworkUses linking devices (hubs or switches) to connect devices to a server
    - Easy add more nodes
    - Robust
  59. 59Packet SwitchingMessage get broken into small data packets
    Sent across network along the most efficient route
    Each packet may take a different route
    Sent with a 'header address' (final destination and sequence for reassembly)
    One packets knows how many packets should be arriving
    Packet fails to arrive the computer requests that the missing packet is resent
  60. 60Packet Switching Advantages- Security
    - Bandwidth used to full potential
    - Different speed devices can communicate
    - Not affected by line failure
    - Availability (no need for direct connection)
    - Text/Emails during a crisis
  61. 61Packet Switching Disadvantages- Delays under heavy use
    - Protocols needed for reliable transfer
    - Not good for some data streams (e.g. real-time video)
  62. 62Circuit Switching3 phases:
    - Establish
    - Transfer
    - Disconnect
    Message sent in one go
    Message arrives in the same order
    Electronic signals pass through multiple switches before a connection is established
    During connection, no other traffic can use those switches
    Resources remain dedicated to the circuit
    Can be analogue or digital
    Shift away from Circuit Swtiching
  63. 63Circuit Switching Advantages- Circuit is dedicated - No interference, no sharing
    - Guaranteed full bandwidth
    - Guaranteed quality of service
  64. 64Circuit Switching Disadvantages- Inefficient
    - Takes a relatively long time to set up the circuit
    - During crisis network may be unavailable
    - Created for voice not data
  65. 65ProtocolsA set of rules for the transmission of data devices
    Allows deviecs to commuunicate regardless of make/design
  66. 66LAN Communicateion ProtoclsNetwork Operating Systems (Ethernet)
  67. 67Access ProtocolsDevice communicates with the network transmission medium (cables)
  68. 68Protocols for Modem CommunicationsSending + Receiving computers must use the same modem protocls and settings if they can communicate
    Both modems must operate at the same speed
    Communication needs:
    - Data transmission rate (slowest of the two)
    - Simultaneously?
    Protocol may also specify:
    - Method to indicate they are finished
    - Methof of data flow control
  69. 69ModemA modem converts the digital data from the computer into a continuous analogue waveform
  70. 70HTTP(HyperText Transfer Protocol)
    Used by the World Wide Web
    How messages are formatted and transmitted, what actions browsers should take in response to bearious commands
  71. 71TCP/IP(Transmission Control Protocol/Internet Protocol)
    Used to connect hosts on the internet
  72. 72TCPEnables two hosts to establish a connection and exchange streams of data
  73. 73IPSpecifies thr form of packets
  74. 74FTP Site(File Transfer Protocol Site)
    A computer which stores files that can be retrieved using FTP
  75. 75Mirror SiteAn FTP site that is created after the original FTP archive servers are copied to it
    Usually larger and faster system than original
  76. 76FTP(File Transfer Protocl)
    - Protocol for excjanging files over the interent
    - Uses the interents TCP/IP to enable sata transfer
  77. 77Cloud ComputingUsing a network of remote servers hosted on the internet to store, manage, and process data, rather than a local server of personal computer
  78. 78How Cloud Computing WorksA cloud provider:
    Hosts a sever with software information and a data centre
    Users can access the software and data from any device with a connection to the internet
  79. 79Advantages of Cloud Computing- Economies of scale (cost of services are spread)
    - No install or updates
    - No need for specialist staff
    - No need to back up data
  80. 80Disadvantages of Cloud Computing- Control of security if given to another party
    - Some risk of losing data if it is under someone else's control
    - Some risk of losing access to the service and havving no local means of recovering it
  81. 81Client-ServerA model wher one entity (the client) requests services from another (the server)
    The server provides services
    (e.g. Storage, E-Mail, Databases)
    Server holds security functions
    (e.g. Logins, Permissions)
  82. 82Client-Side Advantages- All files stored in a central location
    - Users can access shared data
    - Seperates functions, allowing more efficient use of resources
  83. 83Client-Side Disadvantages- Severs are expensive to purchase
    - Specialist staff (e.g. Network Manager) are needed
    - One server faisl = affecrs whole network
  84. 84Peer-to-PeerAll computers have equal status, acting as both clients and server, control is decentralised
    If one computer has a printer connected, all computers on the network can use the printer
  85. 85Peer-to-Peer Advantages- Cheaper than client-server (no need for a server)
    - Easier/Quicker to set up
  86. 86Peer-to-Peer Disadvantages- If a computer with access to a specific device breaks the whole server looses connection to the devices
    - Can become complicated as there are many devices connected to different clients
  87. 87DNS(Domain Name System)
    A hierarchical system, used for private and larger networks
    Resources on TCP/IP network can be named according to ths system so that all have unique names
    Top-level domains are on the right of a resource name (e.g. uk) and the name is further developed as you go left, with each domaink level seperated with a dot ( . )
    The name furthest to the left is the hosts name - The name of the computer where the resouce originates
  88. 88DNS ServerDNS allows users to locate resources using a user-friendly name as an alternative for IP addresses
    A DNS server is a memory bank that contains the relation between IP's and their domain name
    A resource is requested using its URL, which is sent to the DNS servers. The server tries to find the associated IP address associated with the name in its database. If the name is in the server the IP address will be substitued in and the connection is made. Otherwise the DNS server will send the data to another.
  89. 89Serial TransmissionOne bit transmitted at a time through a single computer
    (Safer)
  90. 90Parallel TransmissionA connection for each bit, transmitted simultaneously
    (Faster)
  91. 91SimplexRefers to transmission in only one direction
  92. 92Half-DuplexRefers to the transmission of data in one direction ar a time
  93. 93Full-DuplexRefers to the tranmission of data in two directions

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Descrição
AS level Computing FlashCards sobre 1.3 - Exchange Data - Flashcards, criado por Jack Ives em 01-06-2017.
Criado por
Jack Ives
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Histórico
  • Criado por Nathan Hall · 26 mar 2016
  • Copiado por Jack Ives · 1 jun 2017
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