NOT FOR USE AS AN EXAM SAMPLE COPY - CS(H)15A. National Qualifications. Computing Science D D M M Y Y. Mark. Total marks 90

Transcription

1 FOR OFFICIAL USE National Qualifications Mark CS(H)15A Computing Science Duration 2 hours Fill in these boxes and read what is printed below. Full name of centre Town Forenames(s) Surname Number of seat Date of birth Day Month Year Scottish candidate number D D M M Y Y Total marks 90 SECTION 1 20 marks Attempt ALL questions. SECTION 2 70 marks Attempt ALL questions. Show all workings. Write your answers clearly in the spaces provided in this booklet. Additional space for answers is provided at the end of this booklet. If you use this space you must clearly identify the question number you are attempting. Use blue or black ink. Before leaving the examination room you must give this booklet to the invigilator. If you do not, you may lose all marks for this paper Perfect Papers All rights reserved

2 SECTION 1 20 marks Attempt ALL questions 1. Paul has typed this line of code in his program. Line 201: echo "Your value is ". $score When the code is translated his translation software displays this message: Error found on Line 201: incomplete statement, end of line found - ; expected State the type of programming error that Paul has made Programs make use of parameter passing. Explain the difference between passing a parameter by reference and passing a parameter by value A section of code has been written which examines an array of fifty values. Line 1 SET top TO values[1] 2 FOR index FROM 2 TO 50 3 IF values[index] > top THEN 4 top = values[index] 5 END IF 6 END FOR (a) State the name of the standard algorithm which is shown above. 1 Page two

3 3. (b) When this program is run, the value for top is held in a register. Other than storing a piece of data, state another item that a register could hold Explain the term function This image of a cat is stored in 256 shades of grey. Explain how this image would be stored as a bit-mapped graphic In the design of electronic documents it is important to separate the formatting of the document from the structure of the document. Explain how this is achieved in web page design. 2 Page three

4 7. A sports shop has a database. A table in the database is shown below. item_code category qty_in_stock sale_price description XT3 Training Skipping Rope FG5 Equipment Cross trainer FG5 Training Cross-trainer XT3 Hiking Hiking Boots TR6 Hiking Hiking Boots State a suitable compound primary key for this table Explain how usability testing would be used in the design of a new mobile phone interface Describe a typical phishing attempt (a) State the meaning of the term open source. 1 (b) Other than cost of licensing, state an advantage of using open source software rather than proprietary software. 1 Page four

5 SECTION 2 70 marks Attempt ALL questions 11. A program has been written to find the location of a requested value in a list, however the program does not return the correct location. The algorithm responsible is shown below. Line 1 SET dataset TO [72,34,19,73,52,28] 2 SET location TO 99 3 SET find TO 72 4 FOR counter = 1 TO 6 5 IF dataset[counter] = find THEN 6 SET counter TO location 7 END IF 8 END FOR (a) Line 1 shows the use of a 1-D array to store the list of values, rather than eight individual variables. State two advantages of using a 1-D array to store the list of values. 2 (b) A trace table is being used to record the changes to variables when stepping through the code. (Line 5 does not change a variable s value and so it not included.) Line dataset find location counter 1 [72,34,19,73,52,28] (i) Complete the information in the table above, recording the value assigned to the variable for line 2, 3, 4 and 6. 3 Page five

6 11. (b) (continued) (ii) Explain why the location is never correctly given. 2 (iii) Describe how the algorithm should be corrected. 2 (c) (i) The program is halted at line 4 to allow it to be debugged. State the feature of the software development environment that allows a program s execution to be halted. 1 (ii) Describe how halting the execution of the program will assist with finding errors in the program. 2 Page six

7 12. Gordon is a computing science teacher and is creating a program that delivers a multiple-choice test to his pupils. The test will contain thirty questions and each question has only one correct answer. The test is created in a text file and a sample from the file is shown below: question_text option_a option_b option_c option_d answer What are web pages HTML CSS Java C++ A written with? What is used to view a web page? media player text editor browser debugger C (a) Gordon creates a record data structure for each question. (i) Define a suitable record for a question. 3 (ii) Declare a variable that can store the thirty questions. 2 (b) When running the program an error occurs when reading the file. State one example of an execution error that could occur when reading the text file. 1 Page seven

8 12. (continued) (c) When a pupil uses the program his/her answers are stored in a 1-D array called pupil_answers. pupil_answers A C B Using pseudocode or a language with which you are familiar, write an algorithm for a subroutine that will: Initialise the value for the variable mark calculate the mark from the answers given display the mark on screen. Your algorithm should make use of the variable from (a)(ii). 4 Page eight

9 13. A function is being developed to calculate information about visits to Edinburgh Castle on particular days depending on the weather. (a) The function will make use of formal and actual parameters. Explain each of these terms. 2 (b) Explain how a method is different from a function. 2 Page nine

10 13. (continued) (c) Visitor statistics are recorded for the previous 28 days. For each day, the statistics include the number of visitors on that day and the number of hours of sunshine. Some of the data is shown below: Day Visitors Hours of sunshine The number of visitors for each day is held in an array called visitors and the number of hours of sunshine in sunhours. Using pseudocode or a language with which you are familiar, write an algorithm to count the number of days where the visitor count was greater than 5000 and there were 6 or more hours of sunshine and write this number of days to a text file called sunnydays. 5 Page ten

11 13. (continued) (d) An upgrade is made to the program that the visitor calculator function is part of. When the upgrade is completed it is tested using a virtual machine. Describe two other reasons why a user would use a virtual machine rather than a real computer system. 2 (e) The upgrade was created using Aglie methodologies. Describe two key features of Agile methodologies for software development. 2 Page eleven

12 14. GameOn is an online service which allows computer gamers to record and stream their computer game play in real time to others. The service uses a dynamic database-driven website to display the range of channels and video streams available to viewers. Details of each channel and video are held in a relational database. (a) (i) From the information in the above screenshot, identify two database tables that would be stored in the relational database. 2 (ii) For one of these tables identify three possible attributes and complete the following data dictionary. Table name: Fieldname Type Size 3 Page twelve

13 Question 14. (continued) (b) The GameOn web site is hosted in the public cloud. Explain two advantages of using a public cloud to deploy a site of this kind. 2 (c) Some changes are required to the layout of the site and some new CSS rules are required. Class Font Size (px) Colour (Hex) Style.headings Verdana 14 #FF3399 italic Create a CSS rule using the information in the table above. 3 (d) Compression techniques are applied to the videos on the site. Explain the impact on a stored video of using a lossy compression technique. 2 Page thirteen

14 15. Krazy Karts is a company which organises go-kart driver training and races. Customers can book a course of training sessions with a trainer. At the end of each session each customer in the session races against the others and the trainer records the finishing positions each week. All the information for the company is held in a database with the following tables and fields. Customer League CustomerCourse Course Customer No Customer Name Address LeagueTitle LeagueContact League Gender LeagueTitle*) Date Course Code* Position Customer No* Course Code Course Title Trainer (a) Using the information above create an entity relationship diagram of the Krazy Karts database system. 4 Page fourteen

15 Question 15 (continued) (b) The following report is produced for the system. Customer No: 621 Customer Name: C. Burton Date Course Code Course Title Position 17/02/2014 C cc Karts 4 25/02/2014 C cc Karts 8 05/03/2014 C cc Karts 1 12/03/2014 C cc Karts 3 Describe how the company would use the database software to produce this report. 5 (c) The following form is used to enter the details of customers enrolling. Customer No 123 Customer Name Address Gender League Title* C. Burton 3 Whinfell Lane, Glasgow, G4 6TY c.burton@fre .com Male Super Karts Describe two ways of improving the usability of this form. 2 Page fifteen

16 Question 15 (continued) (d) Explain how the Communications Act (2003) applies to Krazy Karts when they use to market their service to customers. 2 (e) Krazy Karts are environmentally friendly and use lifetime carbon footprint when considering their impact on the environment. Describe what is meant by lifetime carbon footprint in relation to computer systems. 2 Page sixteen

17 16. A web developer has been asked to maintain the web site of a company. (a) The website has been attacked a number of times. On investigation, the web developer finds that the data submitted to the site from web forms is only validated at the client-side. (i) Explain why this allows the site to be attacked. 2 (ii) Explain why server-side validation of online form data would be effective protection against attack. 2 (b) The web developer has been asked to update the web site so that it is displayed correctly on mobile, tablet and desktop computers. The web developer did this using a single cascading style sheet (CSS). Explain how CSS was used to ensure that the site displayed correctly on each device. 2 Page seventeen

18 Question 16 (continued) (c) The web developer has also been asked to ensure that the site is optimised for web search. The following extract of code is from one of the site pages. <html> <head> <title>company Page 1</title> </head> <body> <div class="logoheading"> <img src="mainlogo.png" /> </div> Describe two ways that the web developer could improve this page to ensure it is optimised for web search. 2 (d) For security the company makes use of a digital certificate on their web site. Explain how the use of a digital certificate would reassure users when using a web site. 2 [END OF QUESTION PAPER] Page eighteen

19 [B ADDITIONAL SPACE FOR ANSWERS Page nineteen

20 ADDITIONAL SPACE FOR ANSWERS Page twenty