2. This Question Booklet contains nine questions. Answer any SIX questions.

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1 PROGRESSIVE COMPREHENSIVE HIGH SCHOOL (PCHS) MANKON, BAMENDA 14 FEBRUARY 2014 ADVANCED LEVEL Subject/Code: Computer Science 795 Paper N Paper 2 Examiner DZEUGANG Placide TIME ALLOWED: 2 hours INSTRUCTIONS 1. This Question Booklet is your question paper. Do not write anything therein apart from your name and candidate number 2. This Question Booklet contains nine questions. Answer any SIX questions. 3. All questions carry 20 marks each. For your guidance, the approximate mark for each part of a question is indicated in brackets. 4. You are reminded of the necessity for good English and orderly presentation in your answer. 5. In calculations, you are advised to show all the steps in your working, giving your answer at each stage. 6. Clip board, log tables, slide rules, programmable calculator, cellular phone, pager and electronic gadgets in any form are not allowed. 7. Noiseless and cordless electronic calculators may be used. 8. The Answer Sheet must be handed over to the invigilator before leaving the examination hall. TURN OVER PCHS special mock February 2014/ Computer Science Paper 2 Page 1

2 Question 1 1- The diagram below represents essential features of a computer system. Study the diagram and answer the question the follows: (a) Name the components X, R, S and Q (4mks) (b) In the diagram above indicate the direction of data flow using arrows. (2mks) 2- Explain the concept of pipelining in microprocessor architecture 3- What is a bus width? Explain the influence of the data bus width on the performance of the computer 4- What is the difference between the following concepts (8 mks) (a) multiprocessing and multiprogramming (b) parallel and distributed processing (c) SRAM and DRAM (d) RISC and CISC architecture (at least two differences) Question 2 1. The diagram bellow shows coded data that could be input into a computer (a) What is the name of the above method of input (b) Where would the above method of input be applied? (c) For the application you have given in the above question, state two items of information this type of input may represent. 2- with reasons, briefly describe the most appropriate type of printer or output device for the output of: (6 mks) (a) customer invoices on multi-part stationery (b) letters to customers (c) detailed engineering designs 3- What is a terminal? Name two types of terminal with short description of each 4- State what is meant by each of the following and give an example of where each is used. PCHS special mock February 2014/ Computer Science Paper 2 Page 2

3 (a) Magnetic Ink Character Recognition (MICR) (b) Optical Mark Reader (OMR) 5- Distinguish LCD monitor and CRT monitor Question 3 1- What is structured programming? Name two approaches used in structured programming 2- Differentiate between a local variable and a global variable in programming. 3- What is the importance of program documentation for (4mks) (a) The end-user (b) A programmer 4- Study the following flowchart and answer the questions that follow. (a) Name and represent two programming constructs used in the flowchart (b) What does the flowchart generate as output? Show the dry execution. (c) Write a pseudocode that does the same thing as the flowchart above. Question 4 1- (a) What is a process? (b) Complete the following process state transition diagram and explain any of two transitions. 2- Give one advantage and one disadvantage of one of each the following process management algorithm (a) FCFS (b) SJF 3- Let s consider memory partitions of 100K, 500K, 200K, 300K and 600K (in order) and four processes P1, P2, P3 and P4 of 212K, 417K, 112K and 426K respectively. 100 K 500 K 200 K 300 K 600 (a) For each of the algorithm below, use a diagram to show how processes are allocated to memory partitions. (6 mks) i) first fit, ii) best fit iii) worst fit (b) Which algorithm makes the most efficient use of memory? 4- What is a safe state as for as deadlock is concern? PCHS special mock February 2014/ Computer Science Paper 2 Page 3

4 5- Assume we have nine tape drives. Using the Banker algorithm, consider whether or not the following states are safe or unsafe. Process Current Loan Maximum Need A 0 3 B 3 5 C 4 7 Process Current Loan Maximum Need A 5 7 B 2 5 C 1 3 Question 5 1- Give the acronym name for the following i) BCD ii) ASCII 2- Bit patterns can be interpreted in a number of different ways. A character in a computer is represented by the bit pattern What is its decimal value if it represents: (a) a pure binary integer (b) a BCD (Binary Coded Decimal)? 3- x is a digit such that (2x0) 10 = (x0x) 7. Determine the value of x 4- A particular high-level language supports a type 'string' that is used to represent a sequence of characters stored as ASCII codes. A typical such string variable representing 'ABCDE' is stored in memory in following way. All bytes are shown in hexadecimal. The first byte is not one of the characters of the string Etc. (a) The first byte is not one of the characters of the string. Explain its purpose (2mks) (b) State, with reasons, the maximum number of characters that could be stored in such a string representation (c) Show the memory representation of the string PLACIDE in such a memory(2mks) 5- A burglar alarm system for a house is controlled by a switch. When the switch (S) is on, the alarm (A) sounds if either the front door (F) or back door (B) or both doors are opened. The alarm will not work if the switch is off. (a) Draw the truth table of the circuit managing the alarm burglar system. (b) Find the Boolean function corresponding to the above truth table and simplify it using karnaugh map. (c) Design a circuit of logic gates for the alarm system Question 6 1- Explain briefly the difference between the following concepts with appropriate examples 2- Explain the difference between the user's logical view of the database and the physical database. 3- Using appropriate examples, describe two of the following three types of relationships: i) One-to-one ii) One-to-many iii) Many-to-many PCHS special mock February 2014/ Computer Science Paper 2 Page 4

5 4- Read the following narrative and answer the questions that follow. Get_Well_Soon clinic is a veterinary clinic owned by a few veterinarians in a small rural town. The vets would like to set up a database to keep track of their operations. These operations relate to the clinic s doctors, various animals the veterinarians attend to, and the animals owners. For each Doctor a social security number, name, address, phone number, and salary are maintained. Doctors attend to the animals. A doctor may attend to more than one animal and an animal may be attended to by more than one doctor. Each animal is identified by a unique id. In addition, the kind (such as horse), the gender, and the age of the animal is also maintained. For each owner of an animal, an account number, an address, a phone number, and the balance in the account is maintained. An animal must be owned by exactly one owner, but an owner may own zero or more animal. Required a) Identify all the entities (tables) in the above narrative and the various attributes for each. The primary key should be underlined. (6 mks) b) Prepare an ERD for the above scenario showing all relationship constraints. (5 mks) Question 7 F 0 = 0 1- Let s consider the Fibonacci sequence defined as follow F 1 = 1 F n = F n 1 + F n 2 (a) What is a recursive function? (b) By the use of a graph show the dry execution to calculate F(4) (c) Write a recursive function which calculate F(n) 2- Let s consider the following expression tree (a) Generate the arithmetic expression represented by the tree in postfix, infix and prefix notations (3mks) (b) Explain how a postfix expression can be evaluated with a stack using the following example (a) Explain the principle of selection sort (b) Use the selection sort to sort the following list. All the steps should be given Question 8 1- A company has decided to computerize their operations. They have decided to purchase packages instead of developing their own programs. Give two advantages and two disadvantages of this approach. 2- State three differences between Windows and Linux operating systems PCHS special mock February 2014/ Computer Science Paper 2 Page 5

6 3- (a) Define The Turing Machine and describe its functioning (b) What is the Church-Turing thesis? (c) State what it means by i) Halting problem ii) Computable problem 4- Knowing that a DVR-ROM is 4.7 GB and a CD-ROM is 700 MB, How many CD-ROM do we need to store the content of a full DVD-ROM? (Take 1GB=1024 MB) (3mks) Question 9: 1- Let s consider the following table employee_project below which keeps track of employees working on certain projects Emplyee_project Project Project Employee Employee name Rate Hourly rate number name number category 1023 travel site 11 Vincent Radebe A $ travel site 12 Pauline James B $ travel site 16 Charles Ramoraz C $ estate agency 11 Vincent Radebe A $ estate agency 17 Monique Williams B $50 (a) What is normalization? (b) Justify that the table is in 1NF. (c) What are the rules of the 2NF? Put the table in 2NF (5 mks) 2- Let s consider the following tables (a) What is a primary key? Identify the primary key of each of the tables. (b) Define foreign key and composite key (2mks) (c) Is there any foreign key in one of these tables? Any composite key? (d) What is the result of the following SQL command: i) SELECT title, time FROM Track WHERE Num = 1 ii) SELECT Track.Title, CD.Title FROM Track, CD WHERE CD.cID = Track.cID AND Track.Num = 2 (e) Write the following SQL command i) Find a list of all the CD titles. ii) Find a list of the titles and the time of tracks that are more than 300 seconds long. Your success is in Jesus-Christ!!! PCHS special mock February 2014/ Computer Science Paper 2 Page 6