paper 3 dk

Question 1

Outline the purpose of the Link layer in the TCP / IP protocol suite.

Answer 1

• To ensure correct network protocols are followed
• To enable the upper layers to access the physical medium // enables connection/ communication with the internet / network layer
• To be responsible for transporting data within the network/local segments
• To format the data into frames for transmission
• Maps IP addresses to MAC/Physical addresses.

Question 2

State the reasons for including exception handling routines when writing a program.

Answer 2

• To trap (some) runtime errors
• To prevent a program halting unexpectedly
• To produce meaningful error messages for these errors

Question 3

State how a digital certificate is obtained.

Answer 3

• enquiry made to Certificate Authority (CA)
• enquirer’s details checked by CA
• if enquirer details verified by CA then public key is agreed
• CA creates/issues certificate that includes the enquirers public key
• encrypting data sent to/by CA with the CA’s public/private key

Question 4

Describe the purpose of the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols.

Answer 4

• The SSL and TLS protocols provide communications security over the internet / network
• … they provide encryption
• They enable two parties to identify and authenticate each other
• … and communicate with confidentiality and integrity.

Question 5

Explain how SSL/TLS protocols are used when a client-server communication is initiated.

Answer 5

• An SSL/TLS connection is initiated by an application
• … which becomes the client
• The application which receives the connection becomes the server
• Every new session begins with a handshake
• The client requests the digital certificate from the server
• The client verifies the server’s digital certificate
• …and obtains the server’s public key
• The encryption algorithms are agreed
• The symmetric … session keys are generated / defined

Question 6

insertion sort pseudocode

Answer 6

FOR index<- 1 TO LENGTH(Array)
temp <- Array[index]
count <- index -1
IF MyArray[count] >temp:
WHILE index >=0 AND Array[count]>temp
temp <- Array[count +1]
Array[count +1] <- Array[count]
Array[count] <- temp
Array[count] <- Array[count-1]
count <- count -1
END WHILE
Array[count+1] <- temp
NEXT index

Question 7

Describe what is meant by a declarative programming language.

Answer 7

• Instructs a program on what needs to be done instead of how to do it
• … using facts and rules
• … using queries to satisfy goals.
• Can be logical or functional
• Logical - states a program as a set of logical relations
• Functional – constructed by applying functions to arguments / uses a mathematical style

Question 8

why use user defined data types

Answer 8

built in types arent sufficient to represent data
store data of same or diff types (flexible)
can be encapsulated which ensures consistency and uniformity
Can be reused

Question 9

HTTP process - how its used to request resources

Answer 9

• User types URL
• HTTP transmits request from application to transport (TCP)
• TCP creates packet and sends to destination ports
• DNS server uses domain name to look up IP address
• Server TCP sends back acknowledgement
• Now communication has been established the web server sends the web page back in HTML to the browser
• Browser displays page

Question 10

FTP

Answer 10

• Used to transfer files from one device to another via internet/ networks
• Anonymous ftp - allows the user to access without identifying themself
• Ftp commands - a user can carry out actions that change files on an ftp server eg delete, close, rename
• Ftp server - where files are stored

Question 11

components of ethernet data

Answer 11

• Destination - MAC address of the destination computer
• Source - MAC address of the source computer
• Ethernet type or length
• Frame check - includes a checksum to allow checking of data integrity

Question 12

cluster

Answer 12

a number of computers with SIMD that are networked together
each processor performs a larger pseudo parallel system acting like a super computer

Question 13

use of JK

Answer 13

several can produce shift registers in a comp
simple binary counter can be made by linking JK circuits

Question 14

benefits of intermediate code (code generation)

Answer 14

supports
- use of relocatable code so program can be stored anywhere in main memory
- addition of library routines to minimise storage size
- linking of programs to run together

Question 15

direct memory access controller (DMA)

Answer 15

allows hardware to access main memory independently of CPU
frees up the CPU to allow it to do other tasks while slower I/O operations take place
initiates data transfers - CPU does other tasks at same time
once data transfer is done an interrupt is sent to the CPU from the DMA

Question 16

kernel

Answer 16

central component of OS
responsible for communication between hardware, software and memory

Question 17

how OS hides complexity of hardware

Answer 17

using GUI interfaces
using device drivers (simplifies the complexity of hardware interfaces)
simplifying saving/ retrieving data from memory and storage
carrying out background utilities eg virus scanning

Question 18

page replacement algorithms

Answer 18

first in first out
optimal page replacement
least recently used page replacement
second chance page replacement

Question 19

AI

Answer 19

a machine with cognitive abilities eg problem solving and learning
split into:
- narrow
- general
- strong

Question 20

ML vs DL

Answer 20

ML enables machine to make decisions based on past data - DL uses an ANN
ML only needs a little data to train - DL needs lots
ML identifies most features in data in advance - DL learns features of data from the data itself
ML uses modular approach - DL solves as one entity
ML takes long to test - DL testing is short
ML has clear rules explaining why each models stage was made - DL makes decisions based in its own reasoning - hard to understand (black box)

Question 21

types of back propagation

Answer 21

static
- maps static inputs to static input
- mapping is instantaneous
- training is easier
recurrent
- activation is fed forward until a fixed value is achieved
- not instantaneous mapping
- training is harder

Question 22

regression

Answer 22

way of analysing data before it is input into a system or model
used to make predictions from given data by learning some relationship between the input and the output
used in prediction eg weather forecasting
in ML used to predict the outcome of an event based on any relationship between variables

Question 23

segmentation

Answer 23

space is broken into varying sized blocks called segments
Each segment has a name and size.
During execution segments from logical / virtual memory are loaded into physical memory.
The address is specified by the user
Segments are numbered
… and this number is used as an index in the segment map table.
A segment map table maps logical / virtual addresses to physical addresses

Question 24

Outline how the kernel of an OS acts as an interrupt handler

Answer 24

the kernel receives a signal when an interrupt is generated
the kernel checks the priority and reviews the status/priority of the current interrupts
system enters kernel mode if the type of interrupt is of higher priority than the current process
saves the state of the interrupted process on the kernel stack
the kernel restores the process state e.g. contents of registers once the interrupt is serviced

Question 25

Explain the role of a digital certificate in creating a digital signature.

Answer 25

The digital certificate provides the public key … that can be used to validate the private key associated with the organisation/website/digital signature

Question 26

encapsulation

Answer 26

process of putting data and methods together as a single unit

Question 27

application later

Answer 27

interacts with user used by web browsers enables data transfer to transport defined protocols applications use to allow exchange of data

Question 28

JK flip flop

Answer 28

have J K incput and clock in between have NAND between clock J notQ have NAND between clock K Q then normal flip flop with output of NAND gates

Question 29

JK flip flop outputs

Answer 29

J 0 K 0 remain same J1 K0 0 changes to 1 (same as J) J0 K1 1 changes to 0 (same as J) J1 K 1 1 changes to 0 0 changes to 1 (flips)

Question 30

big O notation bubble sort, insertion sort

Answer 30

O(N^2)

Question 31

Big O time

Answer 31

O(1) O(N) O(N^2) O(2^N) O(logN)

Question 32

big O space

Answer 32

O(1) O(N)