Paper 2 Flashcards
(93 cards)
1
Q
What is the purpose of a start bit in asynchronous serial transmission?
A
Synchronise the receiver’s clock to the transmitter’s clock.
2
Q
What is the purpose of a stop bit in asynchronous serial transmission?
A
Allows the next start bit to be recognised.
3
Q
What is system software?
A
Software used in the management of a computer system.
4
Q
What are four functions of an operating system?
A
Processor Scheduling
Memory Management
IO Controller
Handle Interrupts
5
Q
Why are values stored using floating point always normalised?
A
It maximises precision and gives a unique representation of each number.
6
Q
What is a peer-to-peer network?
A
Each computer has equal status that has shared resources from any computer and has no centralised management.
7
Q
What is it main purpose of a DNS system and how does it work?
A
Translates fully qualified domain names into ip addresses. The DNS stores a database of FQDNs and corresponding ip addresses.
8
Q
Why would assembly language be used?
A
Has a faster execution time and uses less memory.
9
Q
Why would MIDI be used?
A
More compact representation.
Easy to modify.
No data is lost through sampling.
10
Q
What would a thin client need to operate?
A
Higher bandwidth network connection.
Slower processor needed.
The server requires a lot of RAM.
11
Q
Why do desktop computers need secondary storage devices?
A
To store data whilst the computer is off as the contents of the RAM are lost when the computer is turned off.
12
Q
What are the principles of operations of an SSD?
A
Data is stored electronically using trapped electrons which represent 1s and 0s. The type of memory used is NAND memory, where the data is organised into pages.
13
Q
What is the definition of the stored program concept?
A
Serially fetching and executing machine code instructions arithmetically from the main memory by a processor.
14
Q
Advantages of the Harvard architecture?
A
Data and instructions can be accessed simultaneously which leads to increased performance.
Different technologies can be used to implement instruction and data memory.
15
Q
What are registers?
A
Registers are small storage locations which have high read and write speeds used to hold data temporarily.
16
Q
Fetch Part of the Fetch-Execute cycle?
A
- Contents of program counter is copied to the memory address register.
- The contents of the MAR are sent through the address bus to the main memory.
- The contents retrieved are sent through the data bus to the memory data register in the processor.
- The program counter is then incremented by one.
- The contents of the Memory data register are copied to the Current Instruction Register.
17
Q
Decode Part of the Fetch-Execute cycle?
A
The contents of the CIR are decoded in the control unit by separating them into opcodes and operands.
18
Q
Execute Part of the Fetch-Execute cycle?
A
- Any other data that is required is fetched.
- The instruction is carried out by the Arithmetic Logic Unit.
- The output is stored in the accumulator.
19
Q
What are interrupts?
A
A signal which is sent to the processor by an external part of the computer system which requires the processors immediate attention. This suspends the currently executing task.
20
Q
Why do vector graphics take up less storage space?
A
Vectors do not store the colour of individual pixels rather they store properties of the image and the properties to do not take up as much space as storing the colour of individual pixels.
21
Q
Advantages of vector graphics?
A
Individual parts of the image can be manipulated or scaled easily.
22
Q
What is thin client computing and two advantages over thick client?
A
Processing is carried out on an application server. The clients are cheaper due to a lower hardware specification and the modularity of adding another think client is simple.
23
Q
Why is a laser printer with wifi suitable for a small office?
A
Low cost of printing and has a high resolution output.
Printers can be managed remotely and it’s easier to share a printer between many devices.
24
Q
Describe how MIDI is used to represent digital music?
A
Using event messages which can contain the tone, pitch etc of a sound.
25
What are utilities?
Software that performs a specific management function for a computer.
26
What is the role of the control unit?
To control the fetch-execute cycle.
To synchronise operation of processor.
To handle interrupts.
27
Components of a packet?
Source address, destination address, checksum, time to live, data, packet number.
28
Role of a router during packet switching?
Connects two networks together, finds the route with the least congestion and modifies the MAC address for the next hop.
29
Weakness of Caesar Cipher?
Each character is always encrypted to the same character. Therefore the characters in the cipher text will always have the same frequency as the characters in the plaintext.
30
Why is substitution cipher tougher to crack than caesar?
There is no pattern to letter replacements.
31
What is the use of a URL in a RESTful application?
Entering the url causes the server to retrieve the data from the database.
32
SELECT INSERT DELETE UPDATE to REST
GET POST DELETE PUT
33
Why’s JSON sometimes preferred over XML?
It easier to understand by humans and it is compact.
34
Three characteristics of Big Data?
Volume of data is too big to fit on a single server.
Data comes in a variety of forms.
Data generated must be processed at a high velocity.
35
What is synchronous data transmission?
Receiver and transmitter are always synchronised by a common clock.
36
Purpose of the transport layer?
Establishes an end to end connection.
Perform error detection.
Congestion Manager.
Split data up into segments.
Protocols are TCP (Transmission Control Protocol) AND UDP (User Datagram Protocol).
37
What is the additional functionality of a gateway over a router?
Protocol Conversion
38
What is a well known port?
A port that has a specific purpose.
39
Explain asymmetric encryption of a certificate.
A digest is calculated from the contents of the message. Then it is encrypted using A’s Private Key which is now the signature. The signature is appended to the message. Then B’s Public Key is used to encrypt the message again.
B’s Private Key is used to decrypt the first layer then the message is rehashed. A’s Public key is used to decrypt the inner layer and then the digest is checked against the original digest and if it matches the message is received authentically and successfully.
40
Principles of Operation of ADC?
Sound is sample at regular intervals.
Amplitude of each sample is measured.
Each measurement is coded in binary.
41
What is the relationship between software and hardware?
Software are the programs that executes on the hardware.
42
What is DHCP (Dynamics Host Configuration Protocol) used for?
It is used to assign IP addresses to devices as they join a network from a pool of available IP addresses. Once the device leaves the network, the IP address is returned to the pool for allocation to a new device.
43
Advantages of using a DHCP?
Reduces the need for expert knowledge when configuring a host.
Reduces the time required to configure hosts.
Avoid errors.
Facilitates efficient use of a limited pool of IP addresses.
44
How can multiple computers have the same IP address?
Computers have a private IP address which will make use of NAT to replace the private IP with a public IP.
45
Ways that a firewall can protect computers on a LAN?
Block specified protocols.
Block specific IP addresses.
Block certain types of packets.
Use a proxy server to prevent the internet from directly accessing the devices on the LAN.
Identify unusual behaviour from incoming data.
46
Advantages of RFID tags?
Can be read from a greater distance.
Tags don’t need to be manually scanned.
Can be read at a faster rate.
Less easily damaged.
47
Advantages of Barcodes?
Cheaper
Less electronic waste.
Less risk of being accidentally scanned.
Not susceptible to radio interference.
48
What is immediate addressing?
The operand is the datum the instruction should use.
49
What is a high order function?
A function that takes an argument and returns a function as a result.
50
What is the purpose of the application layer?
Selects and uses the correct protocol to transmit data. Protocols are HTTP/S, FTP, SMTP, POP3.
51
What is the purpose of the network layer?
Provides the correct IP addresses for each packet’s source and destination.
Protocols are IP (Internet Protocol) And ICMP (Internet Control Message Protocol).
52
What is the purpose of the link layer?
Controls the physical connections between pieces of hardware in a network. Adds MAC addresses to packets which it receives from the network layer. Protocols are Ethernet.
53
What is a socket address?
A combination of the IP address and port number.
54
How does NAT work?
When a device on a private network wants to communicate with a device on the server, NAT makes a record of the packet before replacing the Private IP with the public IP. When information is received back from the server the public IP is replaced with the matching Private IP that sent the message. This is done because private IPs are not routable.
55
What is port forwarding used for?
When a client needs to communicate with a server connected to a private network with the port they would like to access.
56
What is the client server model?
When clients send request messages to servers which reply to clients with response messages. These messages may be for a confirmation if an action has been completed or not.
57
What is an API (Application Programming Interface)?
It is a set of protocols defining how different applications can communicate with each other.
58
What is the websocket protocol?
It is an API which operates in the application layer used to provide a constant steam of information between two devices such as the clients web browser and a server. It is full duplex meaning data can be sent and received in both directions. It is used for online games and instant messaging by reducing the size of packets for fast transmission of data.
59
What is REST?
Converts HTTP request messages to SQL statements.
60
How does REST work when a client connects to the database?
Client request made to the browser.
Browser responds with required web page with a text file.
Text file contains JavaScript which loads the REST API queries by HTTP requests from client.
Clients sends HTTP request to server.
Server responds with the client’s requests using JSON or XML.
Browser processes the JSON or XML and displays the response to the user.
61
Principles of operation of barcode readers?
A mirror directs light from the laser onto a barcode. The light reflected passes through the lens and is incident on a photodiode which converts light into electrical charge. Light portions reflect the most light and dark sections absorb light therefore corresponding with binary 1s and 0s. This electric charge is measured and processed to form a digital signal representing the contents of the barcode.
62
Principles of operation of a digital camera?
Light is focused on to a sensor with the use of a lens and is regulated with a shutter. A Complementary Metal Oxide Semiconductor (CMOS) or a Charge Couple Device (CCD) both convert the incident light into electrical charge. Charge builds up in a cell which each represent an individual pixel. The charge in each of the cells are measured and converted into a digital value which is then processed by the camera and stored as a digital image. Colour cameras have multiple cells for each pixel each of which consist of a filter to block out certain wavelengths of light. The different intensities of light can be combined to form a full colour.
63
Principles of operation of a laser printer?
Initially a drum is positively charged. Then a laser is directed by a rotating octagonal mirror onto the surface of the drum, discharging certain areas which leaves an impression of the image on the drum. A toner tiller dispense negatively charge toner onto the drum to the positively charged portions of the drum which is applied to a paper as it rolls. The paper is then heated by fusers to fix the toner onto the paper.
64
Principles of operation of RFID?
A reader emits radio waves which is picked up by the antenna on the tag. These radio waves energise the chip which is then used to transmit its contents in the form of its own radio waves back to the reader. These reader decodes the information and is sent to the computer.
65
Principles of operation of a Hard Disk Drive?
A hard disk consists of circular platters made from a magnetic material. Above each platter hovers and actuating arm on which is a read/write head. The read/ write head changes the magnetic polarity of parts of the platter and the actuating arm allows access to all portions of the platter. Data is written in concentric tracks which are further subdivided into sectors.
66
Disadvantages of using a hard disk drive?
They are susceptible to damage from movement due to containing moving parts making them unstable for portable devices.
67
Advantages of a hard disk drive?
Cheap
Provides a lot of storage space
68
How would you increase the capacity of a hard disk drive whilst keeping the same size?
Adding more platters and decreasing the width of tracks.
69
Principles of operation of solid state drives?
SSDs contain NAND flash memory cells and a controller that manages the structure of the data on the drive. NAND flash memory is non volatile there the contents are retained after there is no power supplied. Memory cells are formed of floating gate transistors which store information by trapping electrical charge. Data is stored in pages which are combined to form blocks. SSDs do not overwrite data but completely erase before writing new information.
70
Advantages of SSDs?
No moving parts means higher read and write speeds and lower power consumption therefore suitable for portable devices.
71
Principles of Readable opticals disks?
An optical disk consists of a one single track which spirals outwards from the center to the edge. Pits are burnt onto the disk by a high powered laser which permanently deforms the surface. A low power laser beam is used to reflect off the disk onto a photodiode. The pits scatter the light rather than reflect back therefore the bumps reflect the light back. The pattern can be converted into a digital signal of binary.
72
Principles of a writeable optical disk?
Pattern of reflections are created by an opaque dye rather than pits and bumps. The parts with dye absorb the light whereas the light without reflect. When rewriting data, the photosensitive dye changes from opaque to transparent under a high powered laser.
73
How is a vector graphic stored?
Image is a composition of objects where the properties of each object is stored.
74
What is run length encoding?
A run is a sequence of pixels with the same colour. The sequence is counted which is then stored as a pair of values with the colour of the run.
75
How would you increase the performance of a server by affecting the database or software?
Use an efficient technique for controlling concurrent access such as timestamp ordering, serialisation record locks.
Use a functional programming language for database software.
Ensure the software is compiled rather than executed by an interpreter.
Review conceptual model for inefficiencies such as data redundancy.
Consider if it would be more appropriate to sacrifice normalisation to improve performance.
Use a non-relational database.
76
How would you increase the performance of a server by affecting the design of the computer network?
Use a star topology.
Replace network cable with a higher bandwidth.
Replace all Wifi connections with wired connections.
Increase the number of WAPs.
Consider more efficient protocols.
Replace network cards with a higher bitrate.
77
How does a DHCP communicate with a newly joining device?
Host sends request to discover DHCP server.
DHCP server offers configuration to host.
Host accepts offer of configuration from DHCP server.
DHCP server confirms that configuration has been allocated to host.
78
How is a database usually normalised?
Minimise data duplication.
Eliminate data redundancy.
Eliminate data inconsistency.
79
Challenges that face legislators in the digital age?
Information can be transferred in ways that weren’t previously available before.
Technology evolves quickly making new types of crime possible.
Global nature of internet means crimes can be committed in one country from outside its direct jurisdiction.
Encryption can make it harder to monitor criminal activity.
80
What is a gateway?
Converts information from one protocol to another and transfers it over the web.
81
Difference between a gateway and a router?
A router controls traffic within a network whereas a gateway connects various networks.
82
What is a Fully Qualified Domain Name?
It is the compete address of an internet host or computer.
83
What are internet registries?
They are responsible for the allocation of IP addresses in a world of depleting pool of IP addresses.
84
What is a worm?
A type of malware that can automatically propagate or self-replicate without human interaction.
85
What is the difference between a virus and a worm?
A worm can spread to other computers without human interaction, whereas a virus requires human interaction for it to be sent to another computer.
86
What is a Trojan?
A type of malware that download onto a computer disguised as a legitimate program.
87
What is a client port?
A port that is temporarily assigned for the duration of the connection.
88
What is Port forwarding?
Allows computers in private networks to connect to other computers in other private networks over the internet.
89
Difference between private and public IP addresses?
Public addresses are globally unique.
They are allocated by an Internet Service Provider.
Can be connected directly over the internet.
90
What are the 4 Acts?
The Data protection Act
The Computer Misuse Act
The regulation of Investigatory Powers Act
The communications Act
91
What is the World Wide Web?
A system of interlinked documents accessed via the internet using the HTTP protocol.
92
What is the internet?
A network of interconnected computer networks, using a globally unique address space and an end to end communication protocol.
93
Why must some port numbers be well known?
Particular Port numbers are used to provide a particular service therefore clients must know which port number to connect to.
