9618/31 October/November 2021

Explain the reason why binary numbers are stored in normalised form.

• To store the maximum range of numbers in the minimum number of bytes

• Normalisation minimises the number of leading zeros/ones represented

• Maximising the number of significant bits

• Enables very large / small numbers to be stored with accuracy

Match programming paradigms to their descriptions.

• Declarative –

• Imperative –

• Low-level –

• Object oriented –

• – Programs using the instruction set of a processor

• – Programs that specify the desired result rather than how to get to it

• – Programs using the concepts of class, inheritance, encapsulation and polymorphism

• – Programs with an explicit sequence of commands that update the program state, with or without procedure calls

• Declarative – Programs that specify the desired result rather than how to get to it

• Imperative – Programs with an explicit sequence of commands that update the program state, with or without procedure calls

• Low-level – Programs using the instruction set of a processor

• Object oriented – Programs using the concepts of class, inheritance, encapsulation and polymorphism

Compare sequential and serial methods of file organisation.

• In both serial and sequential files records are stored one after the other and need to be accessed one after the other

• Serial files are stored in chronological order

• Sequential files are stored with ordered records and stored in the order of the key field

• In serial files, new records are added in the next available space whereas In sequential files, new records are inserted in the correct position

Explain how packet switching is used to transfer messages across the internet.

• A large message is divided up into a group of smaller chunks of the same size called packets

• The packet has a header and a payload

• The header contains a source IP address, destination IP address (and sequence number)

• Each packet is dispatched independently and may travel along different routes

• The packets may arrive out of order and are reassembled into the original message at the destination

Outline the function of a router in packet switching.

• he router examines the packet’s header

• It reads the IP address of the destination (from the packet header)

• A router has access to a routing table

  containing information about, e.g., available hops and the status of the routes along the route

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

• The SSL and TLS protocols provide communications security over the internet, they provide encryption

• They enable two parties to identify and authenticate each other and communicate with confidentiality and integrity.

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

• 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 (as defined by the (SSL/TLS) protocols)

• The server sends the digital certificate to the client

State the reason for having multiple hidden layers in an artificial neural network.

• Enables deep learning to take place

• To enable the neural network to learn and make decisions on its own

• To improve the accuracy of the result

Explain how artificial neural networks enable machine learning.

• Artificial neural networks are intended to replicate the way human brains work

• Weights are assigned for each connection between nodes

• The data are input at the input layer and are passed into the system

• They are analysed at each subsequent (hidden) layer where characteristics are extracted.

• reinforcement learning takes place

State three essential features of recursion

• Must have a base case/stopping condition

• Must have a general case which calls itself (recursively)

• changes its state and moves towards the base case

Explain the reasons why a stack is a suitable Abstract Data Type (ADT) to implement recursion.

• A stack is a LIFO data structure

• Each recursive call is pushed onto the stack and is then popped as the function ends.

• Enables unwinding

Identify two Abstract Data Types (ADTs) other than a stack.

• Linked List

• Queue

• Binary Tree