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Computer Science AS Level > 1.3 Exchanging data > Flashcards

1.3 Exchanging data Flashcards

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1
Q

What is the purpose of compression?

A
  • Reduce the size of a file
  • Reduce download times
  • Reduce storage needed
  • Make best use of bandwidth
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2
Q

What are the 2 methods of compression?

A
  • Lossy
  • Lossless
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3
Q

How does lossy compression work on images?

A
  • Stores a lower number of colours or stores larger areas of pixels as a single colour
  • As a result, reduces the quality of the image.
  • A small reduction is barely noticeable, at least by the human eye.
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4
Q

How does lossless compression works?

A
  • Compresses an image to the point where it doesn’t lose quality, as it best works on images where there is a continuous area of the same colour
  • Most effective on vector- style images such as logos and icons
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5
Q

What compression type should you use on text files and executables and why?

A
  • Lossless
  • Because we must not lose any of the data during compression
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6
Q

What are the characteristics of lossy compression?

A
  • Some data is lost when the file is compressed
  • Slightly reduces quality but significantly reduces file size
  • Suitable for images, audio and video
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7
Q

What are the characteristics of lossless compression?

A
  • None of the original data is lost
  • The original file can be recreated when it is uncompressed
  • Suitable for executable files and documents
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8
Q

What is a database?

A
  • An organised collection of data
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9
Q

What is a flat file database?

A
  • A database that contains only a single table, often saved as a CSV file.
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10
Q

What are the benefits of a flat file database?

A
  • Simple to understand
  • Quick to set up
  • Requires little expertise to maintain
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11
Q

Why can flat files become inefficient?

A
  • Repetitive data
  • Repeating data takes up more space in the database, and as the database grows, the situation will get worse
  • If you only used flat file databases, they would soon become difficult to maintain, slow to query and take up unnecessary space
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12
Q

What do 2 tables need to be turned into a relational database?

A
  • A common field
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13
Q

What is a primary key?

A
  • A field in a record that is unique
  • Primary keys serve as unique identifiers for each row in a database table
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14
Q

What are the 3 possible relationships in linking tables?

A
  • One to one
  • One to many
  • Many to many
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15
Q

What is a ERD?

A
  • Entity relationship diagram
  • A sketch of the relationships between databases tables
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16
Q

What is a foreign key?

A
  • Foreign keys link data in one table to the data in another table
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17
Q

How can you capture data?

A
  • Using paper-based data capture form
  • Optical character recognition (OCR)
  • Optical mark recognition (OMR)
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18
Q

How can we design a data capture form to avoid errors and make it as fast as possible?

A
  • Every part of the form labelled clearly
  • Instruction to complete the form in a black pen
  • Instruction to complete the form in capital letters
  • Use of tick boxes
  • Squares for entering each letter separately
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19
Q

How does OCR work?

A
  • Reads text by interpreting the shape of the letters, it works better with printed text rather than handwriting
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20
Q

How does OMR work?

A
  • Often used for multiple-choice tests and lottery tickets
  • Very fast and efficient for collecting data and inputting it in a database
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21
Q

What are examples of selecting data?

A
  • SQL
  • Query by example (QBE)
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22
Q

What do both SQL and QBE allow you to do?

A
  • Specify tables, fields, criteria, output sorting
  • Use boolean expressions
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23
Q

What does a DBMS provide?

A
  • Hides the underlying structure of the data and ensures it remains integral by:
    • Preventing the creation of duplicate primary keys
    • Enforcing validation rules
    • Providing secure access
    • Providing encryption
    • Providing program data independence
    • Managing multiple users
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24
Q

What are the 2 common formats of exchanging data?

A
  • CSV
  • XML
  • JSON
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25
Q

What is EDI?

A
  • Electronic Data Interchange
  • A protocol between 2 systems to facilitate exchange of data
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26
Q

What is a standalone machine?

A
  • A single computer not connected to anything else
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27
Q

What are some advantages of a network?

A
  • Users can share files
  • Users can access files from any computer on the network
  • Users can share peripherals and connections to other networks such as the Internet
  • Communication with other people
  • Servers can control security, software updates and backups of data
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28
Q

What are some disadvantages of a network?

A
  • Increased security risk to data
  • Malware and viruses spread very easily between computers
  • If a server fails, the computers connected to it may not work
  • Computers may run slower if there is a lot of data travelling on the network
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29
Q

What are standards?

A
  • Set of hardware and software specifications that allow manufacturers to create products and services that are compatible with each other
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30
Q

What are some examples of standards?

A
  • HTML
  • Character sets
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31
Q

What is a protocol?

A
  • A set of rules for communication over a network
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32
Q

What are the 3 types of protocol used for communication over LAN/WAN?

A
  • TCP
  • IP
  • UDP
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33
Q

What are the 2 types of protocols used for Web Page requests?

A
  • HTTP
  • HTTPS
34
Q

What is the protocol used for file transfers?

A
  • FTP
35
Q

What are the 3 protocols used for sending/receiving email?

A
  • POP
  • MAP
  • SMTP
36
Q

What do the TCP and IP protocols do?

A
  • The TCP protocol provides error free transmission between two routers
  • The IP protocol routes packets across a WAN
37
Q

What does the UDP protocol do?

A
  • Uses a simple connectionless transmission model
  • It’s an alternative to TCP but has no error checking
  • Used to send short messages using datagrams, where speed is more important than accuracy
38
Q

What do the HTTP/HTTPS protocols do?

A
  • HTTP is a way for a client and server to send and receive requests and deliver HTML web pages
  • HTTPS is the same as HTTP, but it adds in encryption and authentication
39
Q

What does the FTP do?

A
  • Used for sending files between computers, normally on a WAN
40
Q

What do the POP/IMAP/SMTP do?

A
  • Used in conjunction with mail servers to deal with email
  • SMTP transfers ongoing emails between servers and from email clients to servers
  • POP retrieves emails from a mail server and transfers them to your device, and it removes the email from the server
  • IMAP keeps email on the mail server, maintaining synchronicity between devices
41
Q

What is the concept of layers?

A
  • Divide the complex task of networking into smaller, simpler tasks that work in tandem with each other
42
Q

What are the advantages of layering?

A
  • Reduces complex problem into smaller sub-problems
  • Devices can be manufactured to operate at a particular layer
  • Products from different vendors will work together
43
Q

What is the TCP/IP stack?

A
  • Refers to a set of networking protocols consisting of four layers working together
44
Q

What are the 4 layers of the TCP/IP stack?

A
  • Application
  • Transport
  • Internet
  • Link
45
Q

What protocol rules are part of the application layer? What happens at this layer?

A
  • FTP, HTTP, HTTPS, SMTP, IMAP
  • Network applications such as web browsers or email programs operate at this layer
46
Q

What protocol rules are part of the transport layer? What happens at this layer?

A
  • TCP, UDP
  • Sets up communication between 2 hosts - they agree settings such as language and packet size
47
Q

What protocol rules are part of the Internet layer? What happens at this layer?

A
  • IP
  • Addresses and packages data for transmission. Routes packets across the network
48
Q

What protocol rules are part of the link layer? What happens at this layer?

A
  • Copper twister pair, fibre, Wi-Fi
  • Network hardware and connection port standards. OS device drivers also sit there. Facilitates the transmission of binary via any media
49
Q

What is the TCP stack responsible for?

A
  • Establishing an end-to-end connection and maintaining conversations between application processors
50
Q

How do TCP/IP protocols track sessions?

A
  • By using port numbers
51
Q

What happens at the transport layer once the connection is made?

A
  • It splits the data into packets, then it adds to each packet:
    • Its number/sequence
    • The total number of packets
    • The port number that the packet should use
52
Q

What part of the TCP/IP stack does the Internet Layer use?

A
  • IP
53
Q

What does the IP part of the stack add to each packet?

A
  • Source IP address
  • Destination IP address
54
Q

What is a socket?

A
  • IP address + port
55
Q

What happens once data reaches the link layer?

A
  • This layer is responsible for adding the unique MAC address of the source device an destination device
  • When transmitting data between routers over a WAN, the MAC address is changed at each hop on the route
56
Q

What does communication between 2 devices on the same LAN require in terms of layers?

A
  • Link layer which creates a frame using MAC addresses
57
Q

What does communication between 2 devices on the different devices (WAN) require in terms of layers?

A
  • Network layer (which uses IP addresses to create a packet) and link layer frame
58
Q

What do switches do in terms of MAC addresses?

A
  • They learn and store MAC addresses for connected LAN devices only.
59
Q

What do routers do in terms of IP addresses?

A
  • Cache some IP addresses
60
Q

Why do we need both an IP address and a MAC addresses to route traffic over a WAN?

A
  • Because the MAC address is used to show what is needed to be transmitted and the IP address shows where it needs to go roughly
61
Q

How does the DNS work in the context of accessing a website?

A
  1. User requests a URL via a browser
  2. The browser sends the domain name to a DNS
  3. the DNS maps the domain name to an IP address and returns it to the browser
  4. A GET request is sent to the web server using the IP address
  5. The requested web page is returned to the web browser
62
Q

What is a LAN?

A
  • Any network that covers a small geographical area, typically located on a single site
63
Q

Who owns the hardware in a LAN?

A
  • Owned and controlled by the organisation using it
64
Q

What are LANs typically connected with?

A
  • UTP cables
  • Fibre Optic
  • Wi-Fi
65
Q

What is a WAN?

A
  • Any network that covers a large geographical area
  • Could also be defined as multiple LAN’s connected together
66
Q

What are WANs typically connected by?

A
  • Telephone lines
  • Fibre Optic Cables
  • Satellite links
67
Q

What is circuit switching?

A
  • It provides the basis for traditional telephone networks
  • Circuit switching creates a temporary and dedicated link of fixed bandwidth between source and destination that lasts only until the transmission is complete
68
Q

Why can circuit switching be a good choice?

A
  • Guarantees quality of the transmission through dedicated bandwidth, making it excellent for data that needs a constant link end-to-end such as real-time video
69
Q

Why can circuit switching be a bad choice?

A
  • A lot of the potential bandwidth can be wasted
70
Q

What is packet switching?

A
  • Breaks streams of data into smaller blocks, each sent independently of one another
  • At each node, packets are sent via whichever node is the least congested - which maximises bandwidth but doesn’t guarantee the quality of the transmission
  • It also means that packets can take different routes to their destination and may arrive out of order
71
Q

What are the benefits of packet switching over circuit switching?

A
  • Packet switching is more affordable and efficient as all bandwidth can be used at once.
  • It also requires less complex infrastructure and can easily respond if parts of the network fail
72
Q

What are the characteristics of circuit switching?

A
  • It has a physical path between source and destination
  • All packets use the same path
  • Reserves bandwidth in advance
  • Can cause a lot of bandwidth wastage
  • No store and forward transmission
73
Q

What are the characteristics of packet switching?

A
  • It has no physical path
  • Packets travel independently
  • Does not reserve bandwidth
  • No bandwidth wastage
  • Supports store and forward transmission
74
Q

What does a server do in a client-server network?

A
  • Controls access and security for a shared file store
  • Manages access to the Internet
  • Manages printing jobs
  • Provides email services
  • Runs regular backups of data
75
Q

What does a client do in a client-server network?

A
  • Makes requests to the server for data, connections and other services
76
Q

What are some advantages of a client-server model?

A
  • Easier to manage file security
  • Easier to back up shared data
  • Easier to install software updates to all computers
77
Q

What are some disadvantages of a client-server model?

A
  • Can be expensive to set up and maintain
  • Requires IT specialists to maintain
  • The server is a single point of failure
  • Users will lose network access if the server fails
78
Q

What are client-server networks best suited to?

A
  • Organisations with a large number of computers or situations where many computers need access to the same information
79
Q

How does a peer-to-peer model work?

A
  • A peer is a computer connected to the network
  • A peer is equal to all other peers
  • Peers serve their own files to each other
  • Each peer is responsible for its own security and data backups
  • Peers usually have their own printers
  • Peers can send print jobs to another peer to process, but that peer must be switched on to communicate with the printer
80
Q

What are some advantages of a peer-to-peer model?

A
  • Very easy to maintain
  • Specialist staff are not required
  • No dependency on a single computer
  • Cheaper to set up
  • No expensive hardware
81
Q

What are some disadvantages of a peer-to-peer model?

A
  • The network is less secure
  • Users will need to manage their own backups
  • Can be difficult to maintain a well-ordered file store
82
Q

What are peer-to-peer networks best suited for?

A
  • Smaller organisations with fewer computers or where fewer users need access to the same data

Computer Science AS Level (4 decks)

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