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iGCSE Comp Sci Rendcomb 22 > 1.2 Communication and Internet > Flashcards

1.2 Communication and Internet Flashcards

1
Q

What is serial data transmission?

A
  • Method of data transmission
  • each bit is sent one after another …
  • over a single wire (channel)
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2
Q

What is parallel data transmission?

A
  • Method of data transmission
  • Multiple bits (often 8 bits) sent at the same time …
  • using multiple wires (lines)
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3
Q

Advantages and disadvantages of serial transmission are?

A
    • more accurate/fewer errors over a longer distance
    • less expensive wiring (single wire)
    • less chance of data being skewed/out of synchronisation
    • slower, less data sent at once dues to only one wire
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4
Q

Advantages and disadvantages of parallel transmission are?

A
    • less accurate/more errors over a longer distance
    • more expensive wiring (multiple wires)
    • more chance of data being skewed/out of synchronisation
    • faster, more data sent at once due to more wires
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5
Q

Uses of serial transmission?

A
  • Medium to long distances e.g. Ethernet, Telephone Wire
  • USB (Universal Serial Bus)
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6
Q

Uses of parallel transmission?

A
  • Short distances
  • Fast internal data transfer within a computer system (buses)
  • IC’s (Integrated Circuits)
  • Older printers
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7
Q

What is meant by synchronous transmission?

A

Synchronous

  • A continuous stream of data
  • The data is accompanied by timing signals (generated by an internal clock)
  • The clock ensures the sender and receiver are in step with each other
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8
Q

What is meant by asynchronous transmission?

A

Asynchronous

  • Data is transmitted in discrete packets (usually 1 byte)
  • Each packet of data is sent with control bits
  • The control bits allow the receiver to know when the data starts and ends
  • The control bits prevent the packets of data getting mixed up
  • Packets are sent intermittently (they have uneven time intervals between them
  • Slower than synchronous
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9
Q

Explain duplex data transmission and give an example

A
  • Direction of data transmission is both ways at the same time (simultaneously)
  • Examples: Telephone call, broadband connections, video conferencing
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10
Q

Explain half-duplex data transmission and give an example

A
  • Direction of data transmission is both ways but not at the same time (not simultaneously)
  • Examples: Walkie Talkie, Intercom
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11
Q

Explain simplex data transmission and give an example

A
  • Direction of data transmission is one way only (unidirectional)
  • Examples: radio/tv broadcast, microphone to computer, computer to speaker
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12
Q

What are Integrated Circuits?

A
  • self-contained circuits with many separate components (e.g. transistors, diodes) etched into a tiny silicon chip.
  • Uses parallel transmission for …
  • …sending data internally in computer systems
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13
Q

What are the drawbacks of integrated circuits?

A
  • Less flexible - individual component or components cannot be removed or replaced – whole IC must be replaced
  • Limited power rating
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14
Q

What are the benefits of integrated circuits?

A
  • Small size – Thousands times smaller than discrete circuits
  • Small weight due to miniaturised circuit
  • Low cost due to mass production
  • Low power consumption because of their smaller size
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15
Q

What is USB?

A

Universal Serial Bus

  • Uses asynchronous serial transmission for …
  • … sending data externally
  • … (to and from peripherals / between devices)
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16
Q

Advantages of USB are?

A
  • Devices plugged into the computer are automatically detected
  • The connectors can only fit one way; this prevents incorrect connections being made
  • Industry standard; this means that considerable support is available to users
  • Supported by many operating systems
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17
Q

Explain what happens when a USB device is plugged into a computer

A
  • The computer automatically detects a device (due to a small change in the voltage level)
  • A known device is automatically recognised, and the appropriate device driver is loaded
  • If a new device is detected, the computer will look for and install the device driver
  • If this is not available, the user is prompted to download the device driver
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18
Q

Disadvantages of USB are?

A
  • Limited distance: the maximum cable length is presently about 5 metres
  • Current transmission rate is slower than Ethernet (although USB 3.0 is over 10 time faster than USB 2.0)
19
Q

What happens when a USB device is plugged into a computer

A
  • automatic detection
  • the device driver is loaded or downloaded
  • if no driver found to be downloaded the user is prompted to do so
20
Q

What is a web browser?

A

Software that enables users to access resources on the WWW

21
Q

What is HTTP?

A
  • Hypertext Transfer Protocol
  • A protocol that defines how messages are transmitted and formatted over the World Wide Web
22
Q

Describe what is meant by HTTPS

A
  • Hypertext Transfer Protocol Secure
  • A protocol that defines how messages are transmitted (securely) and formatted over the World Wide Web
  • It means data sent to and from the web server is encrypted
  • A locked padlock is shown in the browser
  • It means a website uses TLS/SSL
23
Q

What is a protocol?

A
  • A set of rules that define how devices communicate e.g. HTTP
24
Q

Identify the 3 main parts that make up a URL

A
  • Made up of Protocol, Domain name & file name e.g https://www.bbc.com/index.html
25
Q

What is a URL?

A
  • Uniform Resource Locator
  • The website address typed into a web browser
  • Made up of Protocol, Domain name & file name e.g https://www.bbc.com/index.html
26
Q

Describe what is meant by Domain Name

A
  • A web servers name.
  • Each domain name is unique.
  • Used to identify IP addresses.
27
Q

Describe what is meant by ISP?

A
  • Internet Service Providers
  • Companies that provide the user with access to the internet e.g. Virgin, BT, Sky
28
Q

Describe what is meant by DNS

A
  • Domain Name System
  • Internet service that translates domain names into IP addresses
29
Q

Describe how a DNS server works

A
  • Contains a database of IP addresses
  • When you request an address (URL) …
  • …it looks up the URL in a table and …
  • …returns the corresponding IP address
  • …or searches for the address from another server
30
Q

What is a web server?

A
  • Device that responds to requests to provide information and services over the world wide web
  • Distributes web pages (and other resources) as they are requested
31
Q

Give 3 examples of a server other than a web server

A
  • File server
  • Email server
  • Print Server
32
Q

How does a web browser use the URL to access a web page

A
  • Web browser sends URL to DNS server
  • IP address sent back to web browser
  • Web browser sends request to IP address of web server
  • Web server sends web page to web browser
  • Web browser interprets HTML and displays the web page
33
Q

What is a a NIC?

A
  • Network Interface Card
  • connects a computer to a computer network
  • formats the data sent from the computer into a required format according to the protocols (rules) of the network e.g. TCP/IP.
  • Each NIC has a unique ID known as a MAC address assigned to it
34
Q

Describe what is meant by a MAC address

A
  • Media Access Control
  • Unique ID assigned to a Network Interface Card
  • Hardware address - assigned by a manufacturer
  • It does not change
  • 12 Hex digits e.g. 3A-34-53-C4-69-B8 (First 6 digits Manufacturer ID, Last 6 digits Serial Number)
35
Q

Describe what is meant by an IP address

A
  • Internet Protocol address
  • A unique address for each device on a network / the Internet
  • Software address - allocated by the network
  • It can be
    • static (does not change)
    • dynamic (can change)
  • Two versions
    • IPv4 (32 bit/4 bytes e.g. 172.16.254.1)
    • IPv6 (128 bit/16 bytes)
  • It can be
    • private (used on a local network)
    • public (used by a device on the internet)
36
Q

What are cookies?

A
  • Small packets of data
  • Browsing data stored in a text file
  • Stored by the browser on users computer
  • Used by the website when it is visited again
37
Q

Why do websites use cookies?

A
  • to store personal information
  • to store login details
  • to save items in a shopping basket
  • to customise web pages
  • to track visited websites
  • to carry out targeted advertising
  • to store credit card details
38
Q

What is HTML?

A
  • Hypertext Mark-up Language
  • A web authoring (mark up) language used to create web pages
  • It is uses tags to define the structure e.g. h1, h2, p
  • Note: it can be used for presentation/formatting, but normall CSS
39
Q

What is CSS?

A
  • Cascading Style Sheets
  • Used for presentation
  • Used so that formatting information does have to be included with the content and layout
  • Style sheets hold the formatting information for particular tags e.g.
    • h1 { color: blue; }
40
Q

What are the advantages of CSS?

A
  • Style only needs to be defined once and it is then applied to all instances .
  • Only needs to be changed in one place
  • Same style can be applied to many different documents
  • Pages will load faster as there is less description
41
Q

Why is HTML important?

A
  • It is an accepted standard, so all browsers will display the data correctly.
  • Enables a web browser to interpret a file and display the content
42
Q

Describe the use of structure and presentation in a HTML document

A
  • Structure (HTML) is used to create the layout
    • Mark up tags are used to define the structure (although presentation can be included in the tag)
    • e.g h1, h2, p
  • Presentation (CSS) is used to format colour/style
    • e.g. h1 { color: blue; }
  • Structure and presentation are often kept separate making it easier to update the style
    • A CSS file is linked to a HTML document to define the style of the entire page
43
Q

What is external CSS?

A

CSS: Cascading Style sheets
Seperate CSS files for presentation allow changes to a website style/formatting to only be made in one place.

iGCSE Comp Sci Rendcomb 22 (17 decks)

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