computer studies sec may 2010 marking scheme paper i
Contents
1. of non volatile storage Flash memory 8 Page 7 of 10 SEC COMPUTER STUDIES SSS RES E LEN DO NOT WRITE IN THIS SPACE 11 Consider the flowchart below Start Tot 0 y Read num A N oe Tot Tottnum a If the above algorithm had to be implemented what would the program do 3 The user is repeatedly asked to enter a number until 1 is inputted 1 mark The total of the numbers entered is calculated 1 mark and then displayed on screen 1 mark b Implement the above algorithm in Pascal 9 Program Exam Var Num total integer Page 8 of 10 SEC COMPUTER STUDIES SSS RES E LEN DO NOT WRITE IN THIS SPACE Begin Total 0 Num 0 while num lt gt 1 do begin Writeln Enter a number Readin num Total totaltnum End Writeln the total of the numbers is total End Correct program structure 1 mark Correct syntax 1 mark Correct declaration of variables 1 mark Correct initialization of variables 1 mark Correct use of loop 2 marks Correct use of display and input commands 2 marks Correct summation formula 1 mark c Write code to i Declare an array of TEN integers ii Fill the array with data entered by the user 4 i a array 1 10 of integer ii for i 1 to 10 do readln a i Correct declaration 2 marks Correct use of loo2. Index No MATRICULATION AND SECONDARY EDUCATION CERTIFICATE EXAMINATIONS BOARD UNIVERSITY OF MALTA MSIDA SECONDARY EDUCATION CERTIFICATE LEVEL MAY 2010 SESSION SUBJECT Computer Studies PAPER NUMBER I DATE 3 May 2010 TIME 9 00 a m to 11 00 a m MARKING SCHEME Directions to Candidates Write your index number where indicated at the top of the page Answer ALL questions in the spaces provided You are not allowed to use extra sheets other than those provided in this booklet Good English and orderly presentation are important The use of flowchart templates is permitted The use of calculators is NOT permitted Question 1 2 3 4 5 6 7 8 9 10 11 12 FOR MARKERS USE Number For Markers Total number of Marks or Grade use only obtained by candidate MARKS SEC COMPUTER STUDIES 1 What is the difference between each of the following pairs of items a Transposition errors and transcription errors A transcription error is a specific type of data entry error that is commonly made by human operators or by optical character recognition programs OCR Human transcription errors are commonly the result of typographical mistakes putting fingers in the wrong place during data entry Electronic transcription occurs when the results of a scan of printed matter is compromised or in an unusual font e g if the paper is crumpled or th
3. e ink is smudged when wet the OCR may have a transcription error when reading 1 mark should be awarded for the correct description of either human transcription or electronic transcription error Transposition errors occur when characters have transposed that is they have switched places These types of errors are almost always human in origin Byte and word 1 byte 8 bits 1 word number of bits CPU can process in one operation Compiler and assembler An Assembler converts Assembly instructions into executable machine language whereas a compiler converts higher level programming language instructions into executable machine language Integer and real data types An integer is a number which is whole whereas a real number is one which contains a fractional part i e includes a decimal point Page 2 of 10 SEC COMPUTER STUDIES e CAD and CAM The output from CAD Computer Aided Design is essentially a file describing how something is to be made This maybe for example a picture or the track for a printed circuit board The output from a CAD system maybe the input to CAM Computer Aided Manufacture system CAM is the actual machine which cut and bend metal shape plastics spray paint etc Only 1 mark is awarded if the student gives the meaning of the acronym 10 2 Give one reason why a Passwords are required To prevent unauthorized access to provide security b The Data Protection act
4. f the program such as an incorrect formula Run time error errors detected at run time while program is being executed Ex division by zero 1 2 mark for each description and 2 mark for each example 8 Mention THREE types of documentation which is produced during software development and state why it is needed 6 1 Technical documentation to help in understanding the program structure and how it was coded 2 User manual to aid application users in the running and use of the software package 3 Inline documentation to aid programmers understand how program was written in case and amendments or extensions are needed 1 mark for each type of documentation and 1 mark for its use 9 a Write down the binary equivalent of the hexadecimal number 4A 2 01001010 b If the ASCII code equivalent to the letter A is 6510 which letter does the binary number in part a of this question represent 2 J c What is the largest number that can be stored in an 8 bit register 1 255 or 11111111 127 or 1111111 are also accepted Page 6 of 10 SEC COMPUTER STUDIES 10 Consider the terms below Flash memory Scanner Mouse Modem RAM a Which of the above is a form of volatile storage RAM b Which of the above can translate drawings and photos into digital format Scanner c Which of the above allows digital data to be transmitted over telephone lines Modem d Which of the above is a form
5. h to upgrade it to 1Gb If the memory chips available have a capacity of 256Mb how many of these memory chips will I need to upgrade 2 1Gb 512Mb 512Mb 1 mark Page 4 of 10 SEC COMPUTER STUDIES 512Mb 256Mb 2 1 mark b Mention TWO advantages of having a larger main memory 2 System will be faster More programs may be stored in memory thus may be run apparently simultaneously 6 Describe a problem for which a computer simulation would be a suitable method of solution Explain why a computer simulation would be the most suitable method in this case 3 Flight Simulation 1 mark Since it would be too dangerous and expensive to carry out the task in reality 2 marks 7 a Briefly describe TWO methods of validating data and for each method give an example of invalid data 4 Method 1 Range check to reject any data items outside an expected range Method 2 Type check to ensure that a data item is of a particular data type Allow 2 marks for correct definitions and 2 marks for a valid example b Distinguish between syntax logical and runtime errors amp give an example of each 3 Syntax error occur when program statements cannot be understood by the translator because they do not follow the rules laid down by the programming language ex Missing semi colon at end of statement Page 5 of 10 SEC COMPUTER STUDIES Logical error are mistakes in the design o
6. p 1 mark Correct input statement I mark Page 9 of 10 SEC COMPUTER STUDIES SSS REPO E EN DO NOT WRITE IN THIS SPACE 12 Consider the truth table below A B C X Y Z 0 0 O 0 0 1 0 0 1 0 1 0 0 1 0 0 0 1 0 1 1 0 1 0 1 0 0 0 0 1 1 0 1 0 1 0 1 1 0 1 0 1 1 1 1 1 1 0 Draw the logic circuit corresponding to this truth table 9 This question had a minor mistake The red 0 in the table had to be a 1 In any case after going through some scripts we have come up to this conclusion in marking e Ifthe figure below was drawn give full marks 9 A X Y s L gt p C e Ifthe complete AND gate was drawn give full marks e Ifa note is written that there s an error but nothing else is done give a 5 Page 10 of 10
7. was established To protect the privacy of individuals whose data is being stored c Backups are made So that in the case that the original data becomes corrupted unusable a copy is always available d Software is copyrighted To protect the software s developers rights of distribution So that no parts of code are copied without the author s permission 4 Page 3 of 10 SEC COMPUTER STUDIES 3 Fill in the missing terms in the following statements The ALU performs arithmetic and logical operations b A character code that is widely used in computers is ASCII UNICODE is to be accepted also Two types of optical storage media are compact disc and dvd d A computer s main memory stores both data and instructions e A parity bit is an extra bit that is added to a byte to help detect errors 5 4 a Which communication medium transfers data as pulses of light 1 Fiber optic b List another THEE types of communication media 3 Coaxial cable twisted pair cable and satellite links c Identify TWO advantages and TWO disadvantages of using a wireless network at home no cables or wiring is involved easy for more than one pc to use the same internet connection connection not as reliable as others since it is subject to interference or weak signals data may be viewed by others other people might use your internet connection 4 5 a My computer currently has 512Mb of main memory and I wis
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