JWSS 2018 P1 Solution

Setter: Mr V Surya Class Index Number Name: Jurong West Secondary School Preliminary Examinations 2018 COMPUTING 7155/01 Secondary Four Express 27 August 2018 Paper 1 0800 – 1000 2 hours Candidates answer on the Question Paper. No Additional Materials are required. MARKING SCHEME This document consists of 14 printed pages. 80 _________________________________________________________________________________

2 JWSS Preliminary Examinations 2018 Computing (7155/01) Secondary 4 Express Answer all questions 1 Draw a line to match the computer parts to the correct description. 2 Cloud services allow users to run programs and access data anywhere over the Internet without having to be at a particular physical location. Describe two safety measures you can take to prevent unauthorised access to your private information when using cloud services. (a) Safety measure 1 ……………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. (b) Safety measure 2 ……………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. [2] Safety Measures: • Read and fully understand the privacy policy of the cloud service. • Do not store secret or confidential information on cloud services. • Ensure that the traffic between your device and the cloud service is encrypted before using the cloud service. • Constantly change your cloud passwords Control Unit ALU Secondary Storage Collection of wires for transporting data from one part to another Stores large amount of data that will not be lost when power is interrupted Part of the processor that follows instructions and decides when the data should be stored, received or transmitted Part of the processor that processes data by performing basic mathematical and logical operations [4] CPU Bus ROM

3 JWSS Preliminary Examinations 2018 Computing (7155/01) Secondary 4 Express 3 Insert five of the following words about network devices and components, in the correct place in the text below. client network hub router SSID modem server network bridge port The ……………..…………… number is used together with an IP address to uniquely identify a program that is running on a network. The ……………..…………… is a device that connects multiple devices to the same network and transmits received packets to all connected devices. The ……………..…………… is a device that converts digital signals to analog signals and vice-versa. The ……………..…………… is a 32-bit string that identifies a wireless access point and all devices connected to it. The ……………..…………… is a device that forwards packets between separate networks. [5] 4 When we use a programming language, the source code must be translated into machine code before it can be run. Identify two ways by which source code can be translated into machine code and state an advantage of each method. Method 1 .……………………………………………………………………………. Advantage …….……………………………………………………………….…….. ………………….……………………………………………………………….…….. Method 2 …………………………………………………………………………….. Advantage …….……………………………………………………………….…….. …………....…….……………………………………………………………………... [4] port network hub modem SSID router Using an Interpreter Using a Compiler - Changes to the source code take effect immediately. - Interpreters usually offer an interactive mode, which facilitates learning and experimentation. - The resulting program runs at a faster speed because all the translation has been done beforehand. - The compiler is not needed to run the program after compilation Is complete.

4 JWSS Preliminary Examinations 2018 Computing (7155/01) Secondary 4 Express 5 A meteorologist wants to find out the day and mean temperature recorded, for the hottest day in the month of January, which contains 31 days. State the inputs and outputs required for this problem. Inputs ………………………………………………………………………………... ………….……………………………………………………………………………... Outputs ……………………………………………………………………………... ………….……………………………………………………………………………... Identify two examples of inputs where it may not be possible to find the hottest day in the month of January. Example 1 …….……………………………………………………………….……. ………………….……………………………………………………………….……. Example 2 …….……………………………………………………………….……. ………………….……………………………………………………………….……. [6] 6 Sequence data types allow you to store multiple values in an ordered, organised and efficient fashion. (a) State two sequence data types in Python. (i) ………...…………………….……………………………………………… (ii) ………...…………………….……………………………………………… [2] (b) State two non-sequence data types in Python. (i) ………...…………………….……………………………………………… (ii) ………...…………………….……………………………………………… [2] day_list: list containing all the days of the month temperature_list: list of mean temperatures for each day of the month day of the month hottest mean temperature recorded If the lists are empty, there will be no output If there are two or more days with identical temperatures and deemed to be the hottest, there will be an erroneous output String (str) List (list) Integer (int)/ Float (float) Boolean (bool)

5 JWSS Preliminary Examinations 2018 Computing (7155/01) Secondary 4 Express 7 Data can be corrupted due to a number of reasons. (a) Describe how the following causes can contribute to data corruption and provide a preventive measure for each cause. (i) Human error ...…………….……………………………………………… ….…………………………………………………………………………... Preventive Measure ...…………………………………………………… ….…………………………………………………………………………... [2] (ii) Power failure ...…………….……………………………………………… ….…………………………………………………………………………... Preventive Measure ...…………………………………………………… ….…………………………………………………………………………... [2] (b) To ensure integrity of data during network transmission, parity checks are commonly used for error-checking. (i) The word “be” was sent across the internet. Assuming an odd parity system was used, state if there were any errors in the transmission for each character. Data received ASCII character at destination Was there an error? b 01100010 …………………….…… e 01100101 …………………………. [2] (ii) State one limitation of parity checks. ….…………………………………………………………………………... ….…………………………………………………………………………... [1] YES NO - For instance, it is able to detect that an error has occurred but cannot determine where the error occurred. - If there is a case where more than 1 bit has changed, it will result in correct parity even though the data is actually corrupted When multiple users write to the same file at the same time. Preventive Measure: - Make regular backups of data - Use adequate protection when transporting storage devices - Set up rules when collaborating with multiple users Preventive Measure: - Make regular backups of data - Setup backup power supply (Uninterruptible power supply – UPS) If power supply fails when data is being written to storage device.

6 JWSS Preliminary Examinations 2018 Computing (7155/01) Secondary 4 Express 8 A topology describes the physical layout of a network. Understanding the topology is essential to designing a network. (a) State three common types of network topology. ………………………………………………………………………………….… ………………………………………………………………………………….… [3] (b) A businessman intends to set up a company in town. He wants to have a secure LAN in the office. He has about 140 staff working in the same office while another 20 staff working from offsite locations. The staff need to share files and be able to connect to printers. He also plans to expand his business in the next five years. (i) Which network topology is most suitable in this case? Why? Choice .…………………….……………………………………………… Reason .……….…………………………