MSHS 2018 P1

Class Index Number Name MARIS STELLA HIGH SCHOOL PRELIMINARY EXAMINATIONS SECONDARY FOUR COMPUTING 7155/01 Paper 1 Written 23 Aug 2018 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 a HB pencil for any diagrams or graphs. Do not use staples. paper clips, highlighters, glue or correction fluid. Approved calculators are allowed. Answer all the 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 (a) Convert the denary number 4351 into a hexadecimal number. Show your working. ………………………………………………………………………………………... ……………………………………………………………………………………….. ……………………………………………………………………………………….. [2] (b) Convert the binary number 11010101 into a denary number. Show your working. ……………………………………………………………………………………….. ……………………………………………………………………………………….. ……………………………………………………………………………………….. [2] (c) Describe two common uses of the hexadecimal number system. 1 ……………………………………………………………………………………... ………………………………………………………………………………………... ……………………………………………………………………………………….. 2 ……………………………………………………………………………………... ……………………………………………………………………………………….. ……………………………………………………………………………………….. [4] 2. Insert six of the following words about types of software licences in the correct places in the text below. public proprietary software freeware illegal legal public domain software shareware commercial free and open source software Most ……………………………. software are under legal protection and copyright, and they are also known as ……………………………. . Unauthorised copying is ……………………………. and majority of the source code is kept secret. Only after these legal protection have expired, been surrendered or are simply inapplicable would these programs become …………………………….. . A type of software known as ……………………………. is similar to proprietary software except that it is available for use at no cost. It usually allows users to try a limited version of the software. While ……………………………. is usually the demonstration software that is distributed for free for a specific evaluation period. [6]

3 3 Computer networks are common nowadays. Most homes are equipped with a simple modem and a router to link the mobile devices at home to the same network. Identify two other network devices. In each case, explain the function of the device. Device 1 …………………………………………………………………...…………….... Function ...……………………………………………………………………................... ………………………………………………………………………………...................... ………………………………………………………………………………...................... ………………………………………………………………………………...................... Device 2 …………………………………………………………………...…………….... Function ...……………………………………………………………………................... ………………………………………………………………………………...................... ………………………………………………………………………………...................... ………………………………………………………………………………...................... [6] 4 Your Co-Curricular Activities (CCA) club wants to organise an enrichment activity for its members. Each student is given 3 enrichment activities to choose from. Your club wants to use a computer program to find out which students are interested in which enrichment activity and which is the most popular choice. There are 60 students in the club. State the inputs, the outputs and the processes required to find the most popular enrichment activity and the names of the students who chose that enrichment activity. Inputs …………………………………………………………………………………….... ……………………………………………………………………………………............... ……………………………………………………………………………………............... Outputs …………………………………………………………………………………..... ……………………………………………………………………………………............... ……………………………………………………………………………………............... Processes required …………………………………………………………………….... ……………………………………………………………………………………............... ……………………………………………………………………………………............... [6]

4 5 There are three main types of program errors that can occur in programming. (a) A student was asked to write a program that asks for integer and returns the value of that integer multiplied by 5. The program would be required to check that only numbers are accepted. The student wrote the following code. 1 2 3 4 5 number = input(“Please enter a number. “) while not number.isdigit: number = input(“Please enter numbers only. “) answer = number * 5 print(answer) The student made 2 mistakes in the programming code above. That caused his output to be undesirable. You are required to do the following: • locate which lines the errors are in • for each error, identify what type of error it is • explain why it is an error • what should be done to correct the error Line ………………... Type of Error ……………………………………………………………………….. Description …………………………………………………………………….……. ………………………………………………………………………………….…….. ………………………………………………………………………………….…….. Correction ……………………………………………………………………….….. ………………………………………………………………………………….…….. ………………………………………………………………………………….…….. Line ……………….. Type of Error ……………………………………………………………….………. Description …………………………………………………………………….……. ………………………………………………………………………………….…….. ………………………………………………………………………………….…….. Correction …………………………………………………………………………… ………………………………………………………………………………………... ………………………………………………………………………………….…….. [6]

5 (b) (i) State the third type of error that is not found in part (a). ………………………………………………………………..………………….. (ii) Describe with an example why such an error occurs and what will it cause. ….…………………………………………………………….………………….. ….…………………………………………………………….………………….. ….……………………………………………………………….……………….. ….……………………………………………………………….……………….. [4] 6 Five statements about compilers and interpreters are shown. Tick (√) to show whether the statement refers to a compiler or to an interpreter. Statement Interpreter Compiler Takes one statement at a time and executes it Syntax errors are detected before the program runs Translates the whole program in one go Easier to debug Resulting program runs at a faster speed [5] 7 Pharming is a type of cyber-attack; describe two safety measures that businesses could use to prevent pharming. Safety measure 1 ……………………………………………………………………….... ……………………………………………………………………………………............... ……………………………………………………………………………………............... Safety measure 2 ……………………………………………………………………….... ……………………………………………………………………………………............... ……………………………………………………………………………………............... [2]

6 8 Study the following flowchart of a program very carefully. (a) Complete the trace table for the following two sets of data: (i) a = 18, b = 34, c = 5, d = 55 (ii) a = 5, b = 9, c = 4, d = 1 START y = 1 y = a a = b INPUT a, b, c, d OUTPUT a, b, c, d END is a > b? b = y x = 1 x = 0 y = b b = c is b > c? c = y x = 1 y = c c = d is c > d? d = y x = 1 Yes No Yes No No Yes is x = 1? Yes No

7 a b c d x y OUTPUT