Paper 2

Question 1

What a higher-order function?

Answer 1

A function that takes another function as an argument.

Question 2

Why do rounding errors occur? And what will the system do when the value is converted into binary?

Answer 2

There are not enough bits in the mantissa to represent the value exactly.
It may be truncated- could be rounded to the nearest representable value.

Question 3

Describe the advantages to using Harvard Architecture:

Answer 3

• Avoids bottlenecking of single data.
• Avoids possibility of data being executed as code (can be exploited by hackers).
• Instructions and data can have different word lengths.

Question 4

What is the role of interrupts?

Answer 4

Allows the currently executing task to be suspended so that a source that needs the immediate attention of the processor can be serviced.

Question 5

Why must the volatile environment (the contents of registers) be saved before an interrupt is serviced?

Answer 5

So that the current task can be returned to.

Question 6

What is the relationship between software and hardware?

Answer 6

Software is the program that executes on the hardware.

Question 7

What are the principles and operation of an ADC?

Answer 7

• Analogue signals are sampled at regular time intervals.
• Amplitude of analogue waves measured at each sample point.
• Measurement coded into a fixed number of bits.

Question 8

What are the advantages of floating point?

Answer 8

Can represent numbers with a greater range than a fixed point system (in a given number of bits).

Question 9

What are the advantages of fixed point?

Answer 9

• Can represent some numbers more precisely than a floating point system.
• Calculations can be performed more quickly.
• Represents all numbers to a constant level of precision.

Question 10

What are some reasons why JSON could be argued to be better than XML?

Answer 10

• Easier for humans to understand and read.
• More compact.
• Smaller file size.
• Native support for arrays.
• Quicker to parse.

Question 11

What are some advantages of using the DHCP system?

Answer 11

• Reduces the need for expert knowledge when configuring a host.
• Reduces the time required to configure hosts.
• Avoids errors even as duplicating IP addresses or programming incorrect subnet masks.

Question 12

How can two or more computers connected to the internet have the same IP address and still communicate with each other?

Answer 12

• The computers have private IP addresses.
• NAT will be performed so that the computers can communicate on the internet:
• As data passes onto the internet, private IP addresses are replaced with public addresses of router.

Question 13

What are some ways a firewall can protect computers on a LAN?

Answer 13

• Block traffic on specific ports.
• Block traffic from specific IP addresses.
  -Block certain types of packet.
• Firewall maintains information about current connections and only allows packets relevant to these connection through.

Question 14

What is meant by immediate addressing?

Answer 14

The operand is the value the instruction should use.

Question 15

What is the Stored Program Concept?

Answer 15

Machine code instructions stored in main memory are fetched and executed serially by a processor that performs arithmetic and logical operations.

Question 16

Give the two methods to calculate File Size:

Answer 16

Sample Rate * Sample Resolution * Length of sound

Bit rate * Length of Sound

Question 17

What are the Principles of operation of an ADC?

Answer 17

• Analogue signals sampled at regular time intervals.
• Amplitude of wave measured at each sample point.
• Measurement coded into a fixed number of bits.

Question 18

Advantages of Floating point?

Answer 18

Can represent numbers with a greater range than a fixed point system in a given number of bits.

Question 19

Advantages of Fixed Point?

Answer 19

Can represent some numbers more precisely than a floating point system.

Calculations can be performed more quickly.

Represents all numbers to a constant level of precision.

Question 20

The computer has 4 gibibytes of memory installed. How many kibibytes is this equivalent to?

Answer 20

1024 x 1024 x 4

Question 21

Advantages of using Harvard Architecture to Von Neumann arhcitecture?

Answer 21

• Avoids bottlenecking of single data.
• Avoids possibility of data being executed as code (can be exploited by hackers).
• Instruction and data can have different word lengths

Question 22

What category of system software does a virus checker belong to?

Answer 22

Utilities

Question 23

Describe two different types of resource management that an operating system is responsible for:

Answer 23

• allocate processes
• allocate memory

Question 24

Explain how the transport layer of the TCP/IP stack determines which application layer software on the server should deal with a received request?

Answer 24

The transport layer will use the port number to determine which server/software should deal with the request by adding a port number to the request.

Question 25

Describe the functions of the network layer of the TCP/IP stack:

Answer 25

• adds source IP
• performs routing
• checksum for product header

Question 26

Explain the key difference between lossless and lossy compression:

Answer 26

Original data can be fully recovered if lossless compression has been used.

Question 27

Explain how a paragraph of text could be compressed using a dictionary-based method:

Answer 27

A dictionary is built that maps sequences of characters in the text onto values; the sequences of characters in the text are then replaces by the corresponding values in the dictionary.

Question 28

Explain why dictionary-based compression is not very effective for compressing small amounts of data of text for transmission:

Answer 28

For smaller pieces of text there is little repetition (and so the compressed text will be similar in size to the original).

Question 29

Describe an example of a problem that could occur if no system were in place to manage concurrent access to the database:

Answer 29

-Two users read and edit the source data simultaneously

• only one data is kept

Question 30

How does Timestamp Ordering manage concurrent access?

Answer 30

Timestamps are generated for each transaction. Database records timestamp of last read.

Question 31

Explain what it means for a cipher to be described as being computationally secure:

Answer 31

The cipher cannot be cracked (by any known method) in a polynomial amount of time.

Question 32

What is thin-client computing and why might it be chosen in preference to thick-client system?

Answer 32

Processing is carried out on an application server.
Clients are cheaper to purchase.
Easier to configure/add a new client.

Question 33

What is the relationship between bit rate and baud rate?

Answer 33

Bitrate is twice the baud rate

Question 34

What is the relationship between the bit rate and the bandwidth of the transmission medium that data is transmitted through?

Answer 34

Directly proportional.
Greater the bandwidth, the higher the bit rate.

Question 35

What is the difference between the operation of serial and parallel transmission?

Answer 35

-serial sends one bit at a time/after each other whereas parallel sends multiple bits simultaneously.

• serial uses a single wire whereas parallel uses multiple wires

Question 36

Explain why a laser printer with a built-in wireless network adapter is likely to be a suitable choice of printer for a small office?

Answer 36

Why the laser is suitable:
- low cost per printed page (toner is cheaper)
- toner will not dry out
- prints many pages per minute
- high resolution output

Why the wireless adapter is suitable:
- easy to share printer between many devices
- can connect/print directly from computers (no need to install a network to facilitate wireless printing)
- printer can be managed remotely

Question 37

Describe the principles of operation of a laser printer:

Answer 37

• Bitmap of image built in memory from page descriptor.
• Negative charge applied to photosensitive drum
• laser beam directed at drum
  -mirror is used to direct laser beam
• when laser strikes drum, charge is neutralised
  -negative charge applied to toner
  -toner sticks to drum based on charge/where the laser struck
  -paper passed over drum and toner transfers to it
  -positively charged transfer roller assists transfer of toner from drum to paper
  -heater fuses toner onto paper
• for colour printing, 4 drums are required.