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Flashcards

Computer science all topics part 2

daniel upton English 192 cards

Computer science all topics part 2

Cards in this deck (192)

  1. 1What is a vector graphic and how do they represent imagesA vector graphics are a collection of vectors and functions stored in a list that map out an image. Each vector also stores colour attributes like thickness, opacity and colour
  2. 2What are the advantages and disadvantages of vector graphics compared to bit mapsVector graphics are smaller in file size as the don't store data about each individual pixel. As well vector graphics are scalable as they are a mathematical relationship.
    However the are never going to be as life like as bitmaps.
  3. 3What are bitmaps used for?Realistic images
  4. 4What are vector graphic images used for?Images that are scaled to multiple sizes e.g. advertising
  5. 5What does sample resolution mean in terms of sound?How many different amplitudes can be represented by a single waveform
  6. 6What does sampling rate mean in terms of sound?The amount of measurements made a second
  7. 7What is the Nyquist theorem?an analogue signal waveform may be uniquely reconstructed, without error, from samples taken at equal time intervals. The sampling rate must be equal to, or greater than, twice the highest frequency component in the analogue signal.
  8. 8How do you calculate the size of an audio file?Frequency x bit depth x channels x length of file
  9. 9What is the purpose of an MIDI?To connect devices that control and make sound using MIDI messages
  10. 10What are the advantages of MIDI files?MIDI files are more compact. When embedded in web pages they load quicker. MIDI data is completely editable
  11. 11Why are files compressed?So that they have a lower file size and take up less space
  12. 12What is the difference between lossy and lossless compressionLossy permanently deletes redundant data while lossless temporarily deletes it and if uncompressed will be the exact same while the lossy compressed file will not
  13. 13What are the advantages and disadvantages of lossy and lossless compression?Lossy compression compresses the data more whilst lossless has better quality
  14. 14Explain run length encodingRun length encoding is representing patterns in data by replacing the pattern by how much something occurs in a row
  15. 15Explain how dictionary based lossless compression worksA dictionary is created for each occurrence e.g. a word or a punctuation. Each occurrence is given a unique denary value which has a corresponding binary value. Each occurrence is then replaced in the original source by the denary value
  16. 16Define encryptionEncoding a message so only authorised parties can see it
  17. 17What does cipher ,plaintext and ciphertext mean?Cipher is an algorithm followed to encode or decode a text
    Plaintext is unencrypted text
    Ciphertext is encrypted text
  18. 18Encode the following text using a Caesar cipher with shift 3: miss fellplvv ihoo
  19. 19Decode the following text using a Caesar cipher with shift -2: op eqvvggMr Cottee
  20. 20Why is Caesar cipher easily cracked?Using frequency analysis you can see the most common letters and assume that they are the most common letters in the English language and test the shifts individually
  21. 21Perform Vernam cipher on the letter "F" using a one-time pad of k F = 01000110 k = 0110101101000110
    01101011
    xor = 00101101
    00101101 = -
  22. 22Why is the Vernam cipher considered as a cipher with perfect security?It uses a one time pad which isn't computer generated. The pad is shared in person and both the sender and the recipient destroy their key after using it
  23. 23Compare Vernam cipher with ciphers that depend on computational securityVernam cipher is the only cipher to be mathematically proven to be completely secure. The security of every cipher is based on computational security. In theory everycipher apart from Vernam can be broken given enough cipher text and time
  24. 24What do translators do?Translators convert from one language to machine code
  25. 25What does an assembler and an interpreter convert from?assembler converts from assembly language and an interpreter converts from a high level language
  26. 26Name two low level languagesMachine-code and assembly language
  27. 27Describe machine codeMachine code is a language that uses binary or hexadecimal instructions that the computer understands directly
  28. 28Describe assembly languageAssembly language is a language that uses abbreviations for instructions and uses memory locations or denary values to be operated on
  29. 29What are the advantages and disadvantages of low level languages?Advantages
    programs developed using low level languages are fast and memory efficient
    programmers can utilise processor and memory in better way using a low level language
    No need for a compiler or interpreter so compilation and interpretation times are lower
    low level languages provide direct manipulation of computer registers and storage.
    directly communicate with hardware
    Disadvantages
    Programs aren't portable
    difficult to debug and maintain
    programs are more error prone
    usually results in poor programming productivity
  30. 30What does imperative high-level language mean?A language where code is executed line by line, in a programmer defined sequence of commands and procedures
  31. 31Whats the difference between a interpreter and a compiler?Interpreters directly execute the instructions in the source programming language while a compiler translates the code into efficient machine code
  32. 32When should you use a compiler and an interpreter?An interpreter should be used on small programs whilst the compiler should be used on bigger programs
  33. 33What is bytecode?Bytecode is program code that has been compiled from source code into low-level code designed for a software interpreter
  34. 34What's the difference between source code and object code?Source code is the original code whilst object code is the machine executable file
  35. 35What is the following boolean expression as a circuit and a truth table: ____ _____ Q = (A.B) .(A+B).CWhat is the following boolean expression as a circuit and a truth table: ____ _____ Q = (A.B) .(A+B).C
  36. 36What is the circuit diagram for a half and full adder?What is the circuit diagram for a half and full adder?
  37. 37How does an edge triggered d type flip flop work?On the rising edge of the clock it outputs the current value of the input
  38. 38Give the AND and OR examples for all the boolean algebra and De Morgan lawsIdentity law 1.A = A , 1+A = A
    Null law 0.A = 0, 0+A = A
    Idempotent law A.A = A , A+A = A
    Inverse law A.NOT A = 0, A+NOT A = 1
    Commutative Law AB = BA , A + B = B + A
    Associative Law = (AB)C = A(BC),
    (A+B) + C = A + (B+C)
    Distributive Law = A + BC = (A+B)(A+C),
    (A+B)C = AB + AC
    Absorption law A(A + B) = A, A + AB = A
    Demorgan's law =
    NOT(A.B) = NOT A or NOT B
    NOT(A+B) = NOT A.NOT B
  39. 39What is the processor?The processor is the brains of the computer that performs most calculations take place
  40. 40What is main memory?The memory close to the processor that it can access directly
  41. 41What is an address bus?A collection of wires linking the processor to the main memory that is used to identify particular locations in the main memory
  42. 42What is the data bus?A collection of wires that transport data
  43. 43What is the control bus?The physical connections between the CPU and the internal components that send control information between them
  44. 44Define I/O controllersI/O controllers help in the connection between peripheral devices and the CPU
  45. 45What is the difference between von Neumann and Harvard architecture?von Neumann has only one bus for data transfers and instruction fetches while Harvard has two
  46. 46What are examples of von Neumann and Harvard architecture?Von Neumann is used in general purpose processors whilst Harvard is used in ARM processors and digital signal processing systems
  47. 47What is addressable memory?Special type of memory used for certain very high speed searching applications
  48. 48What is the stored program concept?Machine code instructions stored in main memory are fetched and executed serially by a processor that performs arithmetic and logical operations
  49. 49Define the arithmetic logical unitA component of the processor that performs arithmetic logical and shift operations
  50. 50What is the control unit?A part of the processor that commands all the other parts using control and timing signals
  51. 51What is the system clock?The system synchronises the actions of the processor components using a regular series of ON/OFF signals
  52. 52What are general purpose registers?General purpose registers are fast memory that temporarily store results such as calculations from the arithmetic logical unit
  53. 53What does the current instruction register do?holds the current instruction
  54. 54What does the memory address register do?holds the address in memory where the processor is required to fetch or store data from or to
  55. 55What does the status register do?holds information about the current state of operations. It is used to set flags(carry or overflow) or to detect error conditions
  56. 56What is a processor instruction set?An instruction set specifically for the processor that provides commands to the processor
  57. 57What do interrupt service routines do?interrupts the current active process in the cpu.
  58. 58Explain the following and there effect on processor performance? cores cache memory clock speed word length address bus width data bus widthA core performs actions based on instructions. The more cores the more instructions that can be performed
    Cache memory is the amount of memory close to the cpu that can be used to temporarily store results. The more memory the more can be stored and accessed quickly
    clock speed is the amount of cycles a processor can do per second. The more cycles the quicker instructions are done
    Word length is the length of data that can be sent in one go. The longer word length the more data that can be sent at a time.
    Address buss length is the amount of addresses that can be transported at once. The greater width the more can be transported.
    Data buss width is the amount of data that can be transported at once. The greater width the more data can be sent at once
  59. 59How does a barcode reader work?The sensor in the barcode reader detects the reflected light from the illumination system and generates an analog signal that is sent to the decoder. The decoder interprets that signal, validates the barcode using the check digit and converts it into text. This converted text is delivered by the scanner to a computer software system holding a database of the marker, cost and quantity of all products sold
  60. 60How does a digital camera work?Light from the thing you are photographing goes into the camera lens. This light hits an image sensor chip which splits in up into pixels. The sensor measures the colour and brightness of each pixel and stores it as a number
  61. 61How does a laser printer workA high voltage wire called the corona wire charges up the photo-receptor drum so it has positive charge. At the same time the laser is activated to make it draw the image of the page onto the drum. The laser doesn't move it bounces of a moving mirror. Where the laser hits the drum it removes the positive charge and make the area negatively charged. An ink roller touching the photo-receptor drum coats it with tiny ink particles(toner). The toner has been given a positive electrical charge so it attracts and sticks to the negative part of the drum. an inked image builds up on the drum. A sheet of paper feeds up towards the drum as it moves along it is given a strong positive electrical charge by another corona wire. When the paper moves near the drum it attracts the negatively charged toner particles. The image is transferred from the drum onto the paper. The inked paper passes through two hot rollers. The heat and pressure fuses the toner particles permanently into the fibres of the paper
  62. 62How do RFID tags work?The RFID tags transmit data about an item through radio waves to the antenna reader combination of the scanner. The RFID tags receive energy from the radio waves generated by the reader. When the tag receives the transmission the energy runs through the internal antenna to the tag's chip. The energy activates the chip , which modulates the energy required with the desired information, and then transmits a signal back towards the antenna/reader
  63. 63Why is secondary storage needed?It is non volatile meaning it retains it's contents without the need for a power supply. It also has the large capacity needed to store the operating system and all the programs and files needed by a modern computer system.
  64. 64How does a hard disk work?A read write arm which is an electromagnet moves a long a disk and gives the metal grains of the disk either a positive or negative charge meaning a 1 or a 0. When reading this value is read off by a magnetic reader. The disk is connected to a central spindle which allows the disk to rotate so it can be written on in different places
  65. 65How does an optical disk work?A laser burns a trench into the disk for a 1 and doesn't for a zero. When the disk is being read a laser shines on the disk which reflects back and hits a mirror which is directed at a sensor. If the light hits the sensor it signifies a zero and if it doesn't it signifies a 1
  66. 66How does a solid state disk work?SSD's use a grid of electrical cells. These cells are separated into sections called pages. These pages are where data is stored. pages form together to form blocks.
  67. 67What is serial transmission?Sending one bit after another using one channel
  68. 68What is parallel transmission?Sending multiple bits at a time using multiple channels
  69. 69What are the advantages of serial over parallel transmission?Serial is better at long distances as the data isn't skewed making it more secure. As well it is generally cheaper
  70. 70What is synchronous transmission?All the bits are sent in time with an internal clock pulse
  71. 71What is asynchronous transmission?Each bit is sent as soon as it is available
  72. 72What is the purpose of start and stop bits in asynchronous data transmission?To define the beginning and end of a set of bits
  73. 73Define bandwidthBandwidth is the capacity of a network to transmit the maximum amount of data possible in a given amount of time
  74. 74Define latencyThe time taken for a piece of data to be transmitted
  75. 75Define protocolThe set rules or steps agreed upon to complete a certain task
  76. 76What is the relationship between bit rate and bandwidth?Bit rate is directly proportional to bandwidth
  77. 77Explain how a physical star topology worksAll the nodes are connected to a central hub or switch. Using a hub the data is sent to all the nodes and only the intended node accepts it while with a switch the data is only sent to the intended node
  78. 78Explain what a logical bus topology isA logical bus topology is where the physical topology may be set out like a different network but the data flows like a bus topology
  79. 79Explain how a peer-to-peer network works and when it is used?In a peer-to-peer network each computer has equal status and is connected to each other using the internet. Files can be shared directly between systems on the network. It is generally used for small systems with not that many computers
  80. 80Explain how a client-server network works and when it is usedIn a client-server network most computers are nominated as clients and one or more as servers. The clients request services from the servers, which provide these services. It is used generally everywhere with small and large networks
  81. 81What is the purpose of WiFi?To enable devices to connect to a network wirelessly
  82. 82What components are required for wireless networking?A wireless network adaptor and a wireless access point
  83. 83How are wireless networks secured?Strong encryption of transmitted data using WPA (Wifi Protected Access)/ WPA2.
    SSID ( Service Set identifier) broadcast disabled so unwanted devices can't connect to them. MAC ( Media access Control) address white list
  84. 84Explain wireless protocol carrier sense multiple access with collision avoidance (CSMA/CA) with and(RTS/CTS)A frame is assembled, if the channel is idle a request to send (RTS) is sent if the channel is not idle a random time is waited before checking again. If when the RTS is sent if a Clear to send (CTS) is recieved then the data is transmitted otherwise a random amount of time is waited to try and send the RTS
  85. 85Explain wireless protocol carrier sense multiple access with collision avoidance (CSMA/CA) without (RTS/CTS)A frame is assembled the channel is checked to see if it is idle if the channel is idle then the data is transmitted if the channel idle a random amount of time is waited before checking again
  86. 86What is the purpose of a Service Set Identifier (SSID)To uniquely identify a network
  87. 87What is the structure of the internet?The internet is a large connection of networks linked together by cables and routers
  88. 88What are the main components of a packet?Each packet is sent with the sender's IP and Mac address as well as the Receiver's IP and Mac address in the header. It also has the data of the packet which is in the payload and a Checksum in the trailer so that the data can be checked to see if its corrupt. Furthermore it has the packet sequence number in the header so that the packets can be re arranged if out of order
  89. 89What is packet switching?Packet switching is sending packets on the fastest route possible between the sender and receiver. This is done by sending each packet on the quickest path between routers at that time. This means that different packets from the same sender may go on different path to get to the receiver
  90. 90What is a router?A router is a network device that forwards data packets between similar computer networks
  91. 91What is a gateway?A gateway is a network node that enables traffic to flow in and out of the network and it can also connects two networks that are using different protocols together
  92. 92What does the term URL mean?URL(uniform resource locator) is a web address
  93. 93What does FQDN mean?Fully qualified domain name(FQDN) is a domain name that specifies it's exact location in the tree hierarchy of the Domain name server(DNS)
  94. 94Define domain nameA domain name is a website name that represents the IP address for that website
  95. 95Define IP addressA unique string of numbers separated by full stops that identifies each computer using the internet protocol to communicate over a network
  96. 96Describe how domain names are organisedThe internet corporation for assigned names and numbers (ICANN), maintains domains and IP addresses on the internet. It makes sure that do web pages don't hold the same space in the web
  97. 97What is the purpose and function of the DNS system?The main function of the DNS system is to translate domain names into IP addresses, which computers can understand. It also provides a list of mail servers which accept emails for each domain name
  98. 98What do internet registries do?An internet registry allocates and assigns Ip numbers to device, websites, information systems, autonomous system etc.
  99. 99What is a firewall?A firewall is either software or hardware that controls access to and from a network
  100. 100How does packet filtering work?Packets of data are inspected by the firewall to check which port that are attempting to access. If the packet is to be allowed through the port must be open for the duration of the connection otherwise the firewall will automatically reject it
  101. 101What is Stateful inspection?Stateful inspection examines the payload of a packet before allowing access and remembers actions for future decisions
  102. 102How does a proxy server work?A proxy server makes requests on behalf of your own computer hiding the true request IP addresses from the recipient
  103. 103Explain symmetric encryptionSymmetric encryption uses the same key to encrypt and then decrypt the data being transferred
  104. 104Explain Asymmetric encryptionAsymmetric encryption uses two distinct, yet related keys. One key is the public key which is used encryption and the other is the private key which is used for decryption
  105. 105How are digital certificates obtained and used?The digital certificate is provided by a certificate authority. They are used to verify the identity of the owner of each public key and to obtain the key itself
  106. 106How are digital signatures obtained and used?Digital signatures are created by irreversibly reducing the unencrypted message to produce a hash, then encrypting the hash using their private key. The sender bundles the digital signature with the message and encrypts the bundle using the recipient's public key. The recipient uses their private key to decrypt the bundle. Uses the sender's public key to decrypt the signature. Then compares the hash received in the decrypted signature with their own hash of the received message. If the hashes match, this verifies the integrity of the message
  107. 107What is a worm and how does it work?A worm is a standalone program that does not require a user to run it in order to spread. Worms exploit vulnerabilities in the destination system and spread automatically
  108. 108What is a Trojan and how does it work?Trojans are malicious pieces of software that appear useful. They cannot self replicate and open up back doors in your computer to the internet so that the processing power, internet bandwidth and data can be exploited remotely
  109. 109What is a virus and how does it work?A virus is a small piece of software that piggybacks on real programs. Each time the real program is run the virus runs too and it has the chance to reproduce by attaching to other programs
  110. 110Explain how improvements in code can address worms, Trojans and virusesImproving code quality reduces threats form malware. This is done by the use of two factor authentication, strong passwords, guarding against SQL injection and buffer overflow attack and use of access rights.
  111. 111Explain how monitoring can address worms, Trojans and virusesMonitoring can protect against the threat of hacking which can introduce malware. This is done by using packet sniffers which intercept and log network traffic. The packet sniffers captures the packets and analyse them and present them and present them to the user for the user to make the decision on what should be done with the packet. User access logs can also be used as server admins can see requests form client computers for roles and services on the server
  112. 112Explain how protection can address worms, Trojans and virusesUp to date patches to the operating system and application programs reduce vulnerabilities in the system. As well up to date anti malware software can prevent the spread of infection
  113. 113Describe the application layer of the TCP/IP stackThe application layer is used to provide services for applications that want to communicate across a network, often the internet. It uses high-level protocols that set an agreed standard between the communicating end-points.
  114. 114Describe the Transport layer of the TCP/IP stackThe transport layer uses the transmission control protocol (TCP) to establish an end to end connection with the recipient computer. This is done by splitting the data into packets and numbering them sequentially. It then adds the port number to be used based on HTTP protocol. When receiving this layer confirms that the packets have been received and request any missing packets be resent.
  115. 115Describe the network layer of the TCP/IP stackUses the internet protocol (IP) to address packets with the source and destination IP addresses. A router forwards each packet towards an endpoint called a socket, defined by the combination of the IP address and port number for example 42.205.110.140:80. Each router uses a routing table to instruct the next hop
  116. 116Describe the Link layer of the TCP/IP stackThe link layer operates across a physical connection. It adds the MAC address of the physical Network interface card (NIC) that packets should be sent to based on the destination IP address. The MAC adresses change with each hop
  117. 117What is a MAC address?A MAC address (Media Access control) uniquely identifies a physical device with an NIC
  118. 118What is the port number for the FTP DATA protocol?20
  119. 119What protocol uses port number 25?simple Mail Transfer Protocol (SMTP)
  120. 120What protocol uses port number 110?Post Office Protocol v3 (POP3)
  121. 121What port number does the HyperText Transfer Protocol (HTTP) use?80 and 8080
  122. 122What protocol uses port number 21?File transfer Protocol (FTP) CONTROL
  123. 123What port number does Secure Shell (SSH) Remote login use?22
  124. 124What Protocol uses port 23Telnet (unecrypted) Remote login
  125. 125What port number does the Internet Mail access protocol (IMAP) use?143
  126. 126What protocol uses port number 443?The HyperText Transfer Protocol Secure (HTTPS)
  127. 127What does the FTP protocol stand for and what does it do?File transfer protocol. It is an application level protocol used to move files across a network. Files can be non-anonymously where the user uses a username and password to access the file or the anonymously where any user can access the file
  128. 128What protocol is used to download emails stored on a remote server to a local server?POP3(Post office protocol(v3))
  129. 129What does SMTP stand for and what does the protocol do?Simple Mail transfer protocol. It is used to send emails and forward them between mail servers to their destination
  130. 130What does SSH stand for and what does it do?Secure Shell. Secure shell is an encrypted protocol that allows secure communication between nodes across a network. SSH uses public key encryption to protect the data in communication and is commonly used for remote management of servers and other computers
  131. 131What does HTTP stand for and what does it do?Hyper Text Transfer protocol. It defines how messages are formatted and transmitted, and what actions web servers and browsers should take in response to various commands
  132. 132What does HTTPS stand for and what does it do?HyperText transfer language secure. It is the same as HTTP however all communication between you and your browser is encrypted
  133. 133How is an SSH client used to make a TCP connection to a remote port for the purpose of sending commands to this port using application level protocols for getting HTTP, SMTP commands for sending email and POP3 for retrieving email.I'm sorry I couldn't find any info on this but it's apparently something you need to know
  134. 134How is SSH used to log in securely to a remote computer and execute commands?The computers need an SSH client for the client computer and an SSH daemon for the computer that is being accessed. The SSH daemon is constantly listening to a specific TCP/IP port for possible client connection requests. Once a client initiates a connection the SSH daemon will respond with the software protocol versions it supports and the two will exchange identification data. If the provided credentials are correct, SSH creates a new session for the appropriate environment.
  135. 135Explain the role of an email server in retrieving and sending emailThe server uses the SMTP (Simple mail transfer protocol) to make a connection to the sender's email service so that it can accept the email. It then uses SMTP to transfer the email from email server to email server. It then uses IMAP( Internet Message Access protocol) or POP3 (Post office protocol). IMAP manages the emails on the server so multiple clients can access the same email account in synchronicity. POP3 downloads the email stored on a remote server to a local client and removes it from the remote server
  136. 136Explain the role of a web server is serving up web pages in text formAn web page server uses HTTP to send content to users wanting to view pages of the site
  137. 137What is the role of a web browser in retrieving web pages and web page resources and rendering them accordinglyWhen a browser receives an HTTP response from a webserver the text document containing the HTML, CSS and or Javascript for a page is parsed to break it down to fit a standard hierarchical model. The HTML is broken down into hierarchy of tags called Document Object Model (DOM) tree so the browser can structure the code.The styles from the CSS form their own CSSOM(CSS Object Model) and are related to their corresponding HTML tags. Lastly, any Java script is aprsed and executed
  138. 138What are the two parts that an ip address is split into?A network identifier part and a host identifier part
  139. 139what does a Subnet mask do?A subnet mask is used together with an IP address to identify the network identifier within the address
  140. 140What are the two standards for IP addresses?V4 and V6
  141. 141Why was IPv6 introducedIPv4 provides a maximum of 2^32 or 4.3 billion addresses which isn't enough for the number of devices that need them.
    IPv6 uses 128 bits expressed as a string of 32 hexadecimal digits this means there are 16^32 or 3.48x10^38 possible ipv6 addresses
  142. 142What is the difference between routable and non-routable ip addressesNon-routable ip addresses are used to send data over a network whilst routable ip addresses are used to send data over public networks such as the internet
  143. 143What is the purpose and function of the DHCP systemDynamic Host Configuration Protocol(DHCP) is used to automatically assign IP addresses and any other network configuration information.
  144. 144What is the basic concept of NAT and why is it used?NAT (Network address translation) is used to communicate with the destination ip address on behalf of the host. It is used as Devices using private IP addresses cannot access the internet directly
  145. 145What is the basic concept of port forwarding and why is it used?Using an external router so that public requests can be made onto a private server
  146. 146What is the client server model?The client sends a request message to the server. The server responds to the request by replying with a response message to the client
  147. 147What is the websocket protocol, why is it used and where is it used?The websocket specification defines an API(Application programming interface) establishing a full-duplex 'socket' conncetion between a web browser and a server over TCP. This means that there is a persistent connection between client and server allowing both parties to send data at any time
  148. 148What does CRUD stand for?Create
    Retrieve
    Update
    Delete
  149. 149What does REST to do CRUD?REST enables CRUD to be mapped to database function(SQL) as follows:
    GET -> SELECT
    POST -> INSERT
    DELETE -> DELETE
    PUT -> UPDATE
  150. 150What can JSON or XML be used for?Trasnmit data between a server and web application
  151. 151Where is Javascript referenced by HTML file ran?In the browser
  152. 152What does REST stand for?Representational state transfer
  153. 153What does rest allow javascript to do?talk to the server through HTTP
  154. 154What does JSON stand for?Java script object notation
  155. 155Compare JSON with XMLJSON is easier for a human to read, more compact easier to create and easier for computers to parse and therefore quicker to parse
  156. 156Compare and contrast thin-client computing and thick-client computingThick Clients is to use standard computers as hosts and join them via a network medium. Thin clients use low-powered processors in hosts specifically designed as network machines. Thin is easier to set up, maintain and add terminals. Server software updates can be automatically distributed to each client terminal. It is also more secure. however it is reliant on the server and therefore requires a very powerful and reliable server which increases server demand and bandwidth. Thick is Robust and Reliable. Can operate without a continuous connection to a server and is generally better for running more powerful application. However Higher specification client computers are required. Instillation of software required on each terminal separately and integrity issues with distributed data
  157. 157What are relational databases?A database in which entities have relation with each other and are linked by an extra filed called a foreign key
  158. 158Define attributeAttributes are characteristics in a table
  159. 159Define primary keyIt is a unique entity identifier
  160. 160Define Composite primary keyA primary key which consists of two or more attributes
  161. 161Define foreign keyAn attribute that is common to both tables which is a primary key in one of the table and is used to link the two tables
  162. 162What is required for third normal form?First normal form: Contains no repeating attributes or groups of attributes
    Second normal form : Contains no attributes that depend on only part of the primary key. This only occurs is the primary key is a composite key.
    Third Normal form: Contains no attributes where the value of an attribute is determined by another attribute which isn't part of the key.
  163. 163Write the full command to get the username of the user with user id of "23" from the table userSELECT Username FROM user WHERE User id = 23
  164. 164Write the full command to update the Username of user id "23" to "Cheese" in the table userUPDATE User SET Username = "Cheese" WHERE User id = "23"
  165. 165Write the full command to add a user into the table user with username "Camel" and User id "24"Insert INTO user(User id,Username)
    VALUES (24, Camel)
  166. 166Write the full command to Delete the user Miss fell for the table user who has a user id of "25"DELETE FROM user
    WHERE user id = 25
  167. 167Create a table called user which has two attributes: user id which is an integer and is a primary key and cannot be empty, username which can be any length up to 15 characters and cannot be empty as well.CREATE TABLE user
    (
    user id Integer NOT NULL, PRIMARY KEY,
    username VARCHAR(15) NOT NULL
    )
  168. 168In terms of user access what is useful about a client server database system?It provides access for multiple clients
  169. 169What are the ways that concurrent access can be controlled to preserve the integrity of the databaseRecord locks, serialisation timestamp ordering and commitment ordering
  170. 170Explain record lockingPreventing simultaneous access to objects in a database
  171. 171Explain SerialisationEnsuring that transaction do not overlap by making sure that another transaction doesn't start until the current one is finished
  172. 172Explain time stamp orderingWhenever a transaction starts the it is given a time stamp so that if two transactions affect the same object the earlier one is applied first.
  173. 173Explain commitment orderingTransactions are ordered based on their dependencies on each other as well as the time they were initiated.
  174. 174What are the 3 factors that defines how big data is?Volume : the size of the data
    Velocity : how long it takes to access the data
    Variety : the amount of different types of data
  175. 175What is the most difficult aspect of "big data" and why?The lack of structure. This makes it hard to analyse and it makes relational databases not appropriate because they require the data to fit into a row and column format
  176. 176What must happen to the processing if the data cannot fit onto a single server and what is a programming solution to this problem?The processing must be split across multiple machines however functional programming is a solution because it makes it easier to write correct and efficient code
  177. 177What do functional programming languages support?Immutable data structures
    statelessness
    higher-order function
  178. 178What features make functional easier to write?Correct code
    code that can be distributed over multiple servers
  179. 179What is the fact-based model for representing data?Each fact within a fact based model captures a single piece of information
  180. 180Define a function domainThe set of values from which the function's input values are chosen
  181. 181Define a function Co-domainThe co-domain is a set from which the function's output values are chosen. Not all of the co-domain's members need to be outputs
  182. 182What type of object is a function is functional and imperative programming languages?First class object
  183. 183What does being a first class object mean?It can be an argument to another function as well as the result of a function call
  184. 184What is function application?A function applied to it's arguments for example add(3,4) is applying the function add to the integer arguments 3 and 4
  185. 185What is partial function application?a function which has one argument and the function but not the other argument.
    For example add 4
  186. 186What is composition of functions?Combining two functions to get a new function. For example f(x) = (x+2) and g(x) = x^3 then gf(x) = (x+2)^3
  187. 187What is a higher order function?A function that takes a function as an argument or returns a function as a result or does both
  188. 188What does the function map do?"maps"(applies) a function to each element in the list returning a list of results
  189. 189What does the function filter do?Produces elements in the same data structure as the original which meet a certain criteria
  190. 190What does the function reduce/fold do?Reduces a list of values to a single value by repeatedly applying a combining function to the list of values
  191. 191What does head do to a list?Returns the first item in a list
  192. 192What does tail do to a list?Returns all the items in a list but the first

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Flashcards on Computer science all topics part 2, created by daniel upton on 19/04/2019.
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