DHS 2024 Y6 H2 Computing Prelim Paper 1 Ans Only final

1 (a) Copy and complete the decision table showing all the possible outcomes and results. [4] Ans: Condition 1 2 3 4 5 6 7 8 Has customer been refused insurance by another company? Y Y Y Y N N N N Is car over 10 years old? Y Y N N Y Y N N Has customer make more than 3 claims previously? Y N Y N Y N Y N Action Insurance refused X X - Insurance without discount available X X X X - Insurance with discount available - X [1] [1] [1] [1] (b) Simplify your decision table by removing redundancies. [2] Ans: Condition 1 2 3 4 Has customer been refused insurance by another company? Y Y N N Is car over 10 years old? Y N Y N Has customer make more than 3 claims previously? - - - N Action Insurance refused X Insurance without discount available X X Insurance with discount available X [1] [1] {6} 2 (a) Draw a diagram that shows suitable classes and their relationships for a solution to different payment type for guests of different activity that uses OOP techniques. Include appropriate attributes and methods in each class. [6] Ans: Class names [1] Private attributes [2] Public methods [2] Arrow:[1] (b) What are the benefits of using OOP? [2] Ans: - Reusability: Programs can be assembled from pre-written software components that can be used in many different applications. - Extensibility: New software components can be written or developed from existing ones without affecting the origin components Guest Private: nNo sGuest aCode Public: set_hNo() get_hNo() set_sGuest() get_sGuest() set_aCode() get_aCode() Payment() Member Private: nVisits Public: get_nVisits () set_nVisits () Payment() Non_Member Private: nmVoucher Public: set_Vouchor() get_Vouchor() Payment()

(c) The three key features of the object-oriented approach are often quoted as: [6] (i) Encapsulation [2] Ans: Encapsulation is the mechanism for restricting the access to some of objects' components; this means that the internal representation of an object can't be seen from outside of the objects definition. Access to this data is typically only achieved through special methods. (ii) Inheritance [2] Ans: Inheritance means that one class inherits the attribute and methods from parent class as part of its definition. (iii) Polymorphism [2] Ans: Allows different objects to respond to the same message in different ways, the response specific to the type of object. What do these three features mean? {14} 3 Decomposition and modularity are important concepts in software development. Explain what they mean and how do they benefit in software development. [4] Ans: Max 4 marks Concepts of decomposition. The process of identifying first the major task, them further subtasks within them, is known as functional decomposition or top-down design. [1] • It allows the programmer to concentrate on the overall design of the algorithm without getting too involved with the details of the lower-level modules. [1] • Another benefit of top-down design is that separate modules, once identified and written, are easily understood, can be reused, and can be independently modified if necessary. [1] Concepts of modularity. Modularity refers to the concept of making multiple modules first and then linking and combining them to form a complete system. [1] • Modularity enables re-usability and minimizes duplication. [1] {4} 4 The following questions are not related to each other. (a) State the meaning of privacy of data. [1] Ans: 1 mark for Either • Ensuring data can only be accessed by / disclosed to authorised persons Or • Ensuring data cannot be accessed by / disclosed to unauthorised persons (b) State the meaning of integrity of data. [1] Ans: 1 mark for each bullet point (max 1) • Ensuring the accuracy / completeness / consistency of data (during / after processing) • Ensuring the data is up to date (c) What is the difference between back up and archive? [1] Ans: A backup is a copy of your data that is made to protect against loss of that data while an archive is a copy of data made for long-term storage and reference. (d) What is the advantage of version control in software development? [2] Ans: Version control software keeps track of every modification to the code in a special kind of database. [1] If a mistake is made, developers can turn back the clock and compare earlier versions of the code to help fix the mistake while minimizing disruption to all team members. [1] {5}

5 (a) The server has the IP address 192.168.3.2 Explain why this is not an IPv6 address. [2] Ans: 1 mark for each bullet point (max 2) • Only has four groups of digits // IPv6 has eight groups • Uses dotted notation instead of colons Because it is a 32 bit / 4 byte address // IPv6 is 128 bits / 16 bytes (b) The LAN is set up as a star topology as follow: Describe the function of a router in the network. [2] Ans: 1 mark for each bullet point (max 2) • Receives packets from internet / external network • Implements a firewall • Analyses the destination IP address of each packet • Forwards the packet towards its destination // send packets onto local network or external network • ...using the routing table • Maintains / updates the routing • Allocates private IP addresses • Finds the most efficient route to the destination • Changes the packet format for transmission over the next network // • Network Address Translation (NAT):NAT is a technique used by routers to allow multiple devices in a private local area network (LAN) to share a single public IP address. (c) Explain how data is transmitted between the two laptops in the LAN. [2] Ans: 1 mark for each bullet point (max 2) • The data from the sending laptop is transmitted to the router • The data has address of recipient • The router determines recipient’s destination address • ... by using a routing table The router transmits data directly / only to recipient (d) What does protocol define in computer networks? [2] Ans: Protocols define format and order of messages exchanged and the actions taken after messages are sent or received. (e) Explain the importance of protocol in computer network. [2] Ans: It provides a standardization for manufacturers and organizations to create hardware/software/equipment that are compatible to the version used by the current internet. A violation of protocol will lead to a breakdown of communication. (f) Explain the TCP/IP model and the function of each layer with examples. [4] Ans: Max 4 marks The TCP/IP Model separates networking functions into discrete layers. Each layer performs a specific function and is transparent to the layer above it and the layer below it. [1] 1. Application Layer: supporting network applications, e.g. FTP, SMTP, HTTP [1] 2. Transport Layer: process-to-process data transfer, e.g. TCP, UDP [1] 3. Internet Layer: routing of packets from source to destination, e.g. IP [1] 4. Network Access Layer: support data transmission across the physical network e.g. Ethernet, Wireless 802.11ac/B/G/N [1]

(g) A new online (web) form is to be designed to gather data from customers. Describe the features that must be considered when designing a new form. [3] Ans: Three from: Layout: Use of house style (sensible/appropriate) use of white space/spacing Spaces in fields must be appropriate for the data being collected Structure of the form: Order of the fields to be completed must be logical to user Any connections between fields must be logical/clear/made in the layout Types of input fields: User data is collected by