MSHS 2019 P1

Class/ Index Number / Centre Number/ ‘O’ Level Index Number / Name MARIS STELLA HIGH SCHOOL PRELIMINARY EXAMINATION SECONDARY FOUR COMPUTING 7155/01 Paper 1 Written 28 Aug 2019 2 hours Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your class, index number and name in the spaces at the top of this page. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid. Approved calculators are allowed. Answer all questions. The number of marks is given in brackets [ ] at the end of each question or part question. You should show all your working. The total number of marks for this paper is 80. For Examiner’s Use This document consists of 12 printed pages. 80

2 1 Insert six of the following words or numbers about computers and data in the correct place in the text below. 2 10 16 analogue binary denary digital hexadecimal While ________________________ data is transmitted via fibre optical cables, a computer cannot process this type of data. For a computer to be able to process data, it needs to be converted to ________________________ data. As humans, we mostly use a ______________________ number system; this is a base ______________________ number system. Computers use a ______________________ number system; this is a base ______________________ number system. [6] 2 The three binary numbers in the registers X, Y, Z were transmitted from one computer to another. Parity bit Register X 1 0 0 1 1 0 0 0 Register Y 0 1 1 0 0 1 1 1 Register Z 1 0 0 1 1 0 0 1 One binary number was transmitted incorrectly. This is identified through the use of a parity bit. Identify which register contains the binary number that was transmitted incorrectly. Explain the reasons for your choice. The binary number that was transmitted incorrectly is in Register ……………… Explanation ……………………………………………………………………………………... ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. [4]

3 3 John is writing a program using a high-level language. The program will be published and sold for a profit. (a) John uses an interpreter when creating the computer program. State three features of an interpreter. Feature 1 ………………………………………………………………………………... ……………………………………………………………………………………………. Feature 2 ………………………………………………………………………………... ……………………………………………………………………………………………. Feature 3 ………………………………………………………………………………... ……………………………………………………………………………………………. [3] (b) James writes a similar code and compiled the program when he completed it. Explain two benefits of compiling the program. Benefit 1 ……………………………….………………………………………………... ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. Benefit 2 ……………………………….………………………………………………... ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. [4]

4 4 Consider the logic statement: X = ((A AND B) AND (A OR NOT C)) OR (B AND NOT C) (a) Draw a logic circuit to represent the given logic statement. [6] (b) Complete the truth table for the given logic statement. A B C Working Space X 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 [4] A B C X

5 5 Phishing and pharming are two examples of online security threats to a computer system. (a) Explain what is meant by phishing and pharming. Phishing .……………………………….………………………………………………... .……………………………….………………………………………………................. .……………………………….………………………………………………................. .……………………………….………………………………………………................. Pharming …………………………….………………………………………………..... .……………………………….………………………………………………................. .……………………………….………………………………………………................. .……………………………….………………………………………………................. [4] (b) Identify two other online security threats to a computer system. Security threat 1 …………………….………………………………………………...... Security threat 2 …………………….………………………………………………...... [2] (c) Give two security measures that can help to protect a computer system from online security threats. Security measure 1 …………………….………………………………………………. Security measure 2 …………………….………………………………………………. [2] 6 Darryl stores data electronically. Describe two methods that he could use to avoid loss of stored data. Method 1 ………………………………………………………………………………………... ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. Method 2 ………………………………………………………………………………………... ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. [4]

6 7 The following checks the level of chlorine, depth of water and height of a swimming pool. Error messages are output if a problem is found. START END INPUT Height, Depth, Chlorine OUTPUT “Water too deep” OUTPUT “Water too shallow” OUTPUT “Too much chlorine add more water” OUTPUT “Too little chlorine add more chlorine” OUTPUT “Pool OK to use” Is Depth > Height/2? Is Depth < Height/3? Is Chlorine > 3? Is Chlorine < 1? Is OK == True? OK = True OK = False Yes Yes Yes Yes Yes No No No No No

7 (a) Complete the trace tables for each set of input data. Input data: 6, 2.5, 2 Height Depth Chlorine OK OUTPUT Input data: 4, 3, 1.5 Height Depth Chlorine OK OUTPUT Input data: 6, 3.5, 4 Height Depth Chlorine OK OUTPUT [6] (b) Identify a problem with the algorithm that the flowchart represents. ……………………………………………………………………………………………. ………………………………………………………………………………………… [1] 8 Describe two differences between Read Only Memory (ROM) and Random Access Memory (RAM). Difference 1 …………………………………………………………………………………….. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. Difference 2 …………………………………………………………………………………….. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. [4]

8 9 Five internet terms and six definitions are listed. Draw a line to connect each term to a correct definition. [5] Internet term Definition Browser Internet Service Provider (ISP) Uniform Resource Locator (URL) MAC address IP address A program that allows a user to view webpages The main protocol that governs the transmission of data using the Internet A website address that is typed into the address bar An address given to each device on a network. It is provided by the net