Momaliche COMP M.S. P1

(iii) History button displays the websites that were visited in the recent past Award 1 x 3 = 3 marks 14. (a) Differentiate between absolute and relative cell referencing. (2 Marks) Absolute referencing is a method of referring to a cell such that constant values can be copied across a group of cells. this reference always refers to cells in a specific location of the worksheet cell if they are copied from one cell to another while Relative cell referencing is a method of referring to a cell such a that a formula copied a cross a group of cells changes relative to position of each cell into which it is copied Award 2 x 1 = 2 marks (b) The formula $A$4 + C$5 is typed in cell D4 and copied to cell H6. Write down the formula as it would appear in cell H6. (2 Marks) =$A$+G$5 Award 2 x1 = 2 marks 15. Distinguish between data verification and data validation. (2 Marks) Data verification is the process of checking that data is correctly transcribed while data validation is the process of checking that data entered at input satisfies is correct. Award 2 x1 = 2 marks 3

(b) Draw a flowchart for the pseudocode in 16 (a) above (4 Marks) 6 READ Number Houses=Houses+1 Rent=Period*MRent Is Period>=18? Discount=Rent*0.05 Rent=Rent-Discount STOP Amount=Amount+Rent No Yes Is N=0? Print Amount, Houses Yes No Yes START MRent=0 Houses=0 Amount=0 READ Period

Any 2 correct award ½ x 2 = 1 mark Disadvantages  Network failure paralyses operations  Vulnerable to security threats  Costly software Any 2 correct award ½ x 2 = 1 mark 18. (a) What is the eight bit representation of -78 10 ? (2 Marks) Convert 78 to binary - 1001110 1 Mark Make the number 8 bits – 01001110 ½ Mark Complement the number – 10110001 2 ½ Mark (b) What is the BCD equivalent of 9867 10 (2 Marks) 1001100001100111 2 Award 2 Marks (c) 0110010 2 represents the twos complement of a positive number. Determine the number and give your answer in decimal notation. (3 Marks) Subtract 1 from 0110010 to get the ones complement – 0110001 1 Mark Flip the bits to get the number – 1001110 1 Mark Convert to decimal – 64 + 8 + 4 + 2 = 78 10 1 Mark (d) In a certain 7-bit coding scheme the code for the letter “N” has a decimal equivalent of 78. Determine the code for the letter “Z” using the same coding scheme. (3 Marks) Determine decimal equivalent of N - 91 10 2 Marks Convert 91 10 to binary – 1011011 2 1 Mark (e) State three advantages and two disadvantages of e-commerce. (5 Marks) Advantages  It allows companies to reach a wider market of potential customers, globally, via the company’s web site.  Potential buyers have the ability to source products and services from a wider range of potential suppliers, globally.  The ‘middle man’, usually a physical store, is cut out of the buying process so prices should be cheaper.  Shopping is easy and convenient; it can be done from the comfort of your own home or office.  Automated computerised invoices, tied directly to the purchase made via the web site, mean fewer processing errors. This automation also helps with stock control and accounting. 9

how a computer can perform such magic. She approaches you for an explanation. Explain to her how the computer does this. (3 Marks) (i) Explanation about the computer having a multitasking/multiuser OS – 1 Mark (ii) Explanation of how the operating system switches the control between the various tasks - 2 Marks (b)(i) Define an expert system. (1 Mark) An expert system is a computer program that simulates the judgement and behavior of a human or an organization that has expert knowledge and experience in a particular field. (ii) Describe the three components of an expert system. (6 Marks) The User Interface The user interface is the means of communication between a user and the expert systems problem-solving processes. A good expert system is not very useful unless it has an effective interface. It has to be able to accept the queries or instructions in a form that the user enters and translate them into working instructions for the rest of the system. It also has to be able to translate the answers, produced by the system, into a form that the user can understand. The Knowledge Base The knowledge base stores all the facts and rules about a particular problem domain. It makes these available to the inference engine in a form that it can use. The facts may be in the form of background information built into the system or facts that are input by the user during a consultation. The rules include both the production rules that apply to the domain of the expert system and the heuristics or rules-of-thumb that are provided by the domain expert in order to make the system find solutions more efficiently by taking short cuts. The Shell or Inference Engine The inference engine is the program that locates the appropriate knowledge in the knowledge base, and infers new knowledge by applying logical processing and problem-solving strategies. (c) State two advantages and one disadvantage of using an expert system in passing judgement in courts of law. (3 Marks) Advantages of Expert Systems  Permanence - Expert systems do not forget, but human experts may  Reproducibility - Many copies of an expert system can be made, but training new human experts is time-consuming and expensive  Efficiency - can increase throughput and decrease personnel costs o Although expert systems are expensive to build and maintain, they are inexpensive to operate o Development and maintenance costs can be spread over many users 12