Flashcards
1.3 - Exchange Data - Flashcards
Flashcards do conjunto (115)
- 1HTML(Hypertext Mark-up Language)
A standardised system for tagging text files to achieve font, colour, graphic, and hyperlink effects on web pages - 2CSS(Cascading Style Sheet)
Used to define how web content should be formatted and styled
Easy to make site wide changes - 3JavaScriptA client-side scripting language
Makes pages dynamic and interactive
Can be used for data validations on web forms - 4CompressionThe act of decreasing a files size
Faster download and transfer speed - 5Lossy CompressionRemoves data from the original file
Original files cannot be restored
No noticeable loss of quality (for humans) - 6Lossless CompressionInformation stored is condensed with no loss of data
- 7Lossy Compression ExamplesJPEG
MPEG - 8Lossless Compression ExampleGIF
- 9DatabaseA structured, persistent collection of data
- 10A database must be methodical in order to:- Make processing more efficient
- Reduce storage requirements
- Avoid redundancy - 11EntityA thing of interest to an organisation about which data is to be held
- 12AttributeA property or characteristic of an entity
- 13Flat File DatabaseA single entity contains all data
- 14Relational DatabaseMultiple entities joined by common attributes
- 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 - 16Sequential FileSimilar to serial but can be alphabetical
Makes searching easier
Problem - Unordered -> Ordered? - 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 - 18Variable Length FieldsInsert a marker (e.g. a comma) to delineate (divide) each field
CSV = common
Pro:
- No wasted space - 19HashingKey fields of records can be transformed to generate disk addresses
By taking the last 3 digits from a key
Allows random access - 20Issues with a Flat File Database- Data Redundancy (Repeated data, Wasted Storage Space)
- Data Integrity (Problems with consistency and accuracy) - 21RecordAll the data about and entity
- 22TransactionTo exchange something
- 23Master FileA permanent file, periodically updated, that serves as an authoritative source of data
- 24Transaction FileA collection of transaction records
- 25Relational DatabaseData is stored in separate tables
Each table stores a separate entity
Tables are linked through a relationship - 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
- 27Foreign KeyThe primary key of one data structure placed into a related data structure to represent a relationship, supporting navigation
- 28Secondary KeyAn attribute that could be used for indexing but not for a primary key
(e.g. Postcode, DoB) - 29E-R Diagram(Entity-Relationship Diagram)
A way of representing entities and relationships in a database - 30TupleAn ordered set of data consisting of data in a record
- 31RelationA set of tuples forming a table
- 32DBMS(Database Management System)
Software that creates and maintains a database - 33DBMS Jobs- Database Structure
- Queries
- Views
- Individual Tables
Outputs - 34DBMS Protecting + Maintenance Duties- Organising access rights
- Automating backups
- Preserving referential integrity
- Creating and maintain indexes
- Updating the database - 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 - 36Data IntegrityMaintenance of a state of consistency in the data store, ensuring it is fit for purpose
- 37Data CorruptionOpposite of data integrity (Hardware error, Software error, Electrical glitches, Human error)
- 38Data DictionaryHolds metadata (data about data)
Information on everything needed to make a database function - 39User ViewAppearance + Functionality of the database
Needs a good interface - 40Logical ViewHow data is organised for processing
Construction of tables, reports, queries and the data dictionary - 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 - 42SQLStructured Query Language
- 43DDL(Data Definition Language)
A language to define the structure and instances of a database - 44DML(Data Manipulation Language)
A language for the manipulation of data - 45QBEQuery By Example
- 46Computer NetworkA collection of hardware components and computers (nodes) interconnected by communication channels that allow sharing of resources and information
- 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 - 48Cost of a Private Network- Specialist staff to running + maintain security
- Functionality lost = Potential disaster? - 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 - 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 - 51WAN(Wide Area Network)
A telecommunication network that covers a broad area (i.e. a network that links across metropolitan, regional, or national boundaries - 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 - 53MAC Addressing(Media Access Control Address)
A 48 bit binary unique identifier assigned to a NIC
First 3 octets identify a manufacture - 54RoutersA device that transfers data fro one network to another by forwarding data packets to their destination by the most effective route
- 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 - 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) - 57Ring NetworkAll data sent in one direction around a ring
Each computer is connected to exactly 2 other computers - 58Star NetworkUses linking devices (hubs or switches) to connect devices to a server
- Easy add more nodes
- Robust - 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 - 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 - 61Packet Switching Disadvantages- Delays under heavy use
- Protocols needed for reliable transfer
- Not good for some data streams (e.g. real-time video) - 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 - 63Circuit Switching Advantages- Circuit is dedicated - No interference, no sharing
- Guaranteed full bandwidth
- Guaranteed quality of service - 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 - 65ProtocolsA set of rules for the transmission of data devices
Allows deviecs to commuunicate regardless of make/design - 66LAN Communicateion ProtoclsNetwork Operating Systems (Ethernet)
- 67Access ProtocolsDevice communicates with the network transmission medium (cables)
- 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 - 69ModemA modem converts the digital data from the computer into a continuous analogue waveform
- 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 - 71TCP/IP(Transmission Control Protocol/Internet Protocol)
Used to connect hosts on the internet - 72TCPEnables two hosts to establish a connection and exchange streams of data
- 73IPSpecifies thr form of packets
- 74FTP Site(File Transfer Protocol Site)
A computer which stores files that can be retrieved using FTP - 75Mirror SiteAn FTP site that is created after the original FTP archive servers are copied to it
Usually larger and faster system than original - 76Handshaking2 devices intiate communication
One device sends a message indicating it wishes to establish a communication channel
Devices send several messages back and forth and agree on communication protocols - 77FTP(File Transfer Protocl)
- Protocol for excjanging files over the interent
- Uses the interents TCP/IP to enable sata transfer - 78Cloud ComputingUsing a network of remote servers hosted on the internet to store, manage, and process data, rather than a local server of personal computer
- 79SaaS(Software as a Service)
A software delivery method that provides access to software and its functions remotely as a web based service - 80How 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 - 81Advantages 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 - 82Disadvantages 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 - 83Client-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) - 84Client-Side Advantages- All files stored in a central location
- Users can access shared data
- Seperates functions, allowing more efficient use of resources - 85Client-Side Disadvantages- Severs are expensive to purchase
- Specialist staff (e.g. Network Manager) are needed
- One server faisl = affecrs whole network - 86Peer-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 - 87Peer-to-Peer Advantages- Cheaper than client-server (no need for a server)
- Easier/Quicker to set up - 88Peer-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 - 89LayeringA divide and conquer strategy
- A useful way to solve complex problems
- Problems broken down into componets
- For network it helps to develop the infrastructure necessary to support robust systems
- Different aspects are conceptualised and developed seperately
- Each component part (layer) focuses on one aspect of the network without focusing on the others
- Each layer only communicates with the layers next to it
Must consider
- What is being communicated?
- Who is it being sent to?
- How will it get there? - 903-Layer Abstraction of a networkUseful to provide a model of real-life situation into which we can design prposed solutions
1) Application Layer
- Collecting and distributing data
2) Network Layer
- Concerened with layout of the network, the topology being used, how to transfer data efficiently
3) Physical Layer
- Data transfered by some medium (e.g. cables, NIC, routers, etc)
- Provides a transport medium to communicate the messages as the network layer instructs it - 91OSI(Open Systems Interconnection)
An open standard for worldwide communications that defines a networking framework for implementing protocols in seven layers - 92OSI (Application Layer)The closest layer to the user
Collects/Delivers data and passes it to and from the presentaion layer - 93OSI (Presntation Layer)Looks after the conversations between data as sent on the network and data as it is needed by the application
May involve encryption/decription operations - 94OSI (Sessions Layer)Looks after starting, managing and terminating connection sessions
Provides simplex, half-duplex, and full duplex operation - 95OSI (Transport Layer)Concerned with keeping track of segmaents of a nerwork, checking successfull transmissions and bindling daya into packets according to a specific protocol (e.g. TCP)
- 96OSI (Network Layer)Transmission of data packets
Routing - 97OSI (Data Link Layer)Control of access
Error detection and correction - 98OSI (Physical Layer)Network devices and trsnamission media
- 99TCP/IP (Application Layer)- Production, Communication + Reception of data
- Data = Acceptable format for appplications to use it
- Includes the means of packaging the data and handling to the transport layer (HTTP, FTP)
(OSI --> Application, Presentation, Session) - 100TCP/IP (Transport Layer)- Concerned with the esablishment + termination of connections between network entities via routers
- Provides a reliable flow of data
(OSI --> Transport) - 101TCP/IP (Internet Layer)- Links to transmit datagrams across different networks
- Concerned with individual network types allowing the transfer of data between any networks
IP used here - defining the nature of IP addresses - directs datagrams from one router to the next
(OSI --> Network) - 102TCP/IP (Link Layer)- Concerened with passing datagrams to the local physical network
- Makes the overeall network hardware independant, can operate over any transmission medium (e.g. copper wire, wireless, optical fibre, etc)
(OSI --> Data Link, Physical) - 103TCP/IPA complete set of many protocols covering data transmission accross a network
Goverens how data should be:
- Formatted
- Addressed
- Routed
- Received - 104DatagramsSelf-contained, independent entity of data that carries sufficient information to be routed from the source to the destination without reliance on earlier exchanges between the source and destiantion and transporting networks
- 105DNS(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 - 106DNS 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. - 107Error CheckingA procedure used to check that data is recieved as it was transmitted as data can become corrupt through transfer (it is necessary to maintain data integirty)
- 108Checksum1) Data is transfered in binary numbers
2) The numbers are added together (carries out of byte are ignored)
3) Sum is sent with the data
4) Once received data is added again
5) If both sums are the same it can be assumed that the data is not corrupt - 109Echoing Back1) A checking message sends back the data to the sending device
2) Data sent back is compared to original data
3) Echo back if diffferent (error has occured, data is retransmitted)
4) Echo process is then repeated
(Very Slow) - 110Parity CheckingData is sent in bytes
1) First 7 bits = data
2) 8th bit = parity bit
3) Parity check makes the no. of 1's in the byte always odd or even
4) Odd or even = Established on connection
5) Will discover error in a byte (2 error = excepted) - 111Serial TransmissionOne bit transmitted at a time through a single computer
(Safer) - 112Parallel TransmissionA connection for each bit, transmitted simultaneously
(Faster) - 113SimplexRefers to transmission in only one direction
- 114Half-DuplexRefers to the transmission of data in one direction ar a time
- 115Full-DuplexRefers to the tranmission of data in two directions
Informações
- Descrição
- A2 - Level A2 Computer Science FlashCards sobre 1.3 - Exchange Data - Flashcards, criado por Nathan Hall em 26-03-2016.
- Criado por
- Nathan Hall · mar 2016
- Atualizado
- 10 jun 2016
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