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)
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)
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
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
5
Q
Uses of serial transmission?
A
- Medium to long distances e.g. Ethernet, Telephone Wire
- USB (Universal Serial Bus)
6
Q
Uses of parallel transmission?
A
- Short distances
- Fast internal data transfer within a computer system (buses)
- IC’s (Integrated Circuits)
- Older printers
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
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
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
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
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
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
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
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
15
Q
What is USB?
A
Universal Serial Bus
- Uses asynchronous serial transmission for …
- … sending data externally
- … (to and from peripherals / between devices)
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
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
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.
