2. Communication and internet technologies

Question 1

What is half-duplex data transmission?

Answer 1

Both directions, one at a time

Question 2

What is full-duplex data transmission?

Answer 2

Both directions at the same time

Question 3

Example of simplex

Answer 3

Data being sent to a printer

Question 4

Example of half-duplex

Answer 4

Walklie-talkies

Question 5

Example of full-duplex

Answer 5

Phone conversation

Question 6

What is serial data transmission?

Answer 6

Data is sent one bit at a time down a single channel

Question 7

What is parallel data transmission?

Answer 7

Several bits of data are sent simultaneously down multiple channels

Question 8

Example of serial

Answer 8

Between a computer and a modem; USB

Question 9

Example of parallel

Answer 9

Buses within computer hardware

Question 10

Advantages of serial

Answer 10

Works well over long distances

No issues with synchronisation

Question 11

Disadvantages of serial

Answer 11

Slower

Question 12

Advantages of parallel

Answer 12

Faster

Question 13

Disadvantages of parallel

Answer 13

Can become skewed over long distances

Question 14

What is asynchronous data transmission?

Answer 14

Data is grouped together and sent with control bits

Question 15

What is simplex

Answer 15

One direction only

Question 16

What is synchronous data transmission?

Answer 16

Data is sent in a continuous stream with timing signals

Question 17

Advantages of asynchronous

Answer 17

Don’t have to worry about timing

Question 18

Advantages of synchronous

Answer 18

Faster

Question 19

What happens when a USB is plugged into a computer?

Answer 19

The computer detects that a device is connected and loads up the appropriate driver. If a new device is connected the computer will look for the appropriate driver to download.

Question 20

Advantages of USB

Answer 20

Devices automatically detected
Very standard
Only fit one way - cant be broken in this way

Question 21

How does a parity check work?

Answer 21

The sender and receiver decide to use either even or odd parity. A parity bit is allocated in the byte. The bit is either a 0 or 1 to give an even or odd number of 1s in the data. The receiver checks this is true and, if it is not, requests that the data is resent.

Question 22

How does a parity table work?

Answer 22

Each byte is given a parity bit and a parity byte is attached as well.

Question 23

Disadvantages of parity checks

Answer 23

Can’t locate error (unless in table)

If multiple bits are corrupted it wont be detected

Question 24

How does an automatic repeat request work?

Answer 24

When the receiver receives the data correctly it sends an acknowledgement back to the sender. If the acknowledgement is not received before the timeout the data is automatically resent.

Question 25

How does a checksum work?

Answer 25

Data is sent in blocks with an additional block for the checksum. Before the data is sent, the checksum for the bytes is calculated. When the data is receive, the checksum is calculated again using the same algorithm and compared to the checksum sent. If they are different, a request is sent for the data to be resent.

Question 26

How does an echo check work?

Answer 26

When the data is received, it is automatically sent back to the sender and then compared to the original. If they are not the same the data is resent.

Question 27

Disadvantage of echo check

Answer 27

Don’t know whether the error was made in the first or second time the data was sent.

Question 28

What is an internet service provider?

Answer 28

A company that provides users with internet access for a monthly fee.

Question 29

What is an IP address?

Answer 29

A 32 bit number assigned to a computer when it connects to the internet and is unique for that session.

Question 30

Which IP addresses don’t change?

Answer 30

Those of web servers.

Question 31

What is a MAC address?

Answer 31

A unique number that identifies a device connected to the internet.

Question 32

What is the difference between HTML presentation and structure?

Answer 32

Structure includes the meaning and layout of the document, presentation is the style of the document.

Question 33

What is http?

Answer 33

Hypertext transfer protocol is a set of rules that must be obeyed when data is transferred across the internet.

Question 34

What is the function of a web browser?

Answer 34

Interpret HTML code from websites into something the user can view.