Computing (Modular) CP5
2008
 (2 Hours)

[1](i) State the computer term for an area of memory where data is temporarily stored while being transferred between a keyboard and a computer. [1]
   
(ii) Give a different example of where such an area of memory would be used in a computer system, stating clearly the relative speeds of the devices concerned. [2]
 
 
[2](a) Wide area networks can use circuit switching or packet switching to transmit data from a source work station to a destination work station.  
(i) Explain in detail how data is transmitted from source to destination using circuit switching. [2]
(ii) Explain in detail how data is transmitted from source to destination using packet switching. [3]
(iii) State one advantage of using packet switching rather than circuit switching. [1]
(b)       A ring network uses a token to communicate with other stations on the network. The token is continuously passed from station to station.
(i) Give one disadvantage of a ring network topology compared to a bus network. [1]
(ii) When data is being transmitted, the token will contain actual data and check data. State another item that must be included in the token. [1]
(iii) Explain in detail how data is sent from the source to the destination using token passing on a ring network. [3]
 
[3] A holiday company allows customers to search for holidays using the company's website. After the customer has selected a holiday they move to a new page where they can book the holiday. The master file  is then updated to indicate that a booking has been made. A copy of every booking transaction is stored in a separate file called a transaction log.
(i) Explain how the system would stop two customers booking the same holiday. [1]
(ii) If the master file becomes corrupted, the holiday company would not know which customer had booked which holiday. Explain in detail how the transaction log could be used to restore the corrupted master file. [2]
 
[4] The operating system of a multi-user computer has to manage the computer's  resources.
(i) Explain in detail how the operating system uses time slicing to allocate processor time to user tasks. [2]
(ii) Partitioning is used when allocating main memory. Explain in detail the term partitioning. [2]
(iii) Explain the meaning of the computer term interrupt and give two examples of situations where interrupts may occur. [3]
 
[5](a) A particular indexed sequential file uses a three level index. Explain in detail, with the aid of a diagram how a record is located using the three indexes. [3]
(b) Give one advantage of using an indexed sequential file rather than a direct access file [1]
(c) Explain in detail how a record is located using a hashing algorithm when the record is stored in the overflow area, [4]
(d) How will accessing a record in the overflow area affect the access time? [1]
 
[6] Each year students enrol on many college courses. The data is stored in a database which has not been normalised; some of the data is inconsistent. An example of the data is shown below.
Student
Number		 Name Address Tel Num DOB Course Title Course
Cost		 Start Date
101 Ian Smith 22 Apple Drive 0111 555444 29/07/88 AS Level Physics £200 08/09/07
101 Ian Smith 22 Apple Drive 0111 555444 29/07/88 AS Level Chemistry £200 08/09/07
123 Jane Jones 31 Farm Road 0123 656565 17/03/87 GCSE Mathematics £95 15/09/07
101 Ian Smyth 22 Apple Drive 0111 555444 29/07/88 AS Level Photography £350 08/09/07
123 Jane Jones 31 Farm Road 0123 656565 17/03/87 GCSE English £95 15/09/07
123 Jane Jones 31 Farm Road 0123 656565 17/03/87 GCSE Spanish £95 15/09/07
136 Harry Stien 44 Tree Street 0499 333242 22/05/71 GCSE Spanish £95 15/09/07
123 Jane Jones 31 Farm Road 0123 656565 17/03/87 GCSE History £95 15/09/07
........ ........ ........ ........ ........ ........ ......  
(a) Using an example of inconsistent data from the above table, explain what is meant by the term data inconsistency. [2]
(b) How could the possibility of this database containing inconsistent data be removed? [1]
(c) A definition of third normal form is 'data items are dependant on the primary key only and dependant on the whole of the primary key'.
Using an example from the above data, which is not normalised, explain why this data is not in third normal form. [1]
 
[7] Car engines are controlled by a computer system called the engine control unit (ECU). The ECU has several inputs.
(a)(i) The ECU uses feed-back to control the engine. Explain in detail what is meant by the term feed-back [2]
(ii) Describe one benefit of using a computer system to control the engine. [1]
(b)(i) Explain the difference between analogue and digital signals. [1]
(ii) One input to the ECU is the engine temperature. Explain why analogue to digital conversion will be required to monitor the engine temperature. [1]
 
[8](a) Data can be transmitted along a data line in two different ways, either one bit after the other or by simultaneously transmitting more than one bit at the same time. State the name of each of these data transmission methods. [1]
(b) Data can be transmitted along a data line in both directions at the same time. State the name of this data transmission method. [1]
(c) Explain the need for multiplexing in a computer system. [1]
 
9.  (i) A recording company has recording artists who produce albums. Each album contains many singles and each recording artist produces many albums.
The company need to know which artist has released which album and what singles are on each album.
Design a three-table database for recording artists, albums and singles in third normal form to handle the information required for this application
You should clearly indicate suitable table names and any primary of foreign keys that you use. [8]
(ii) The recording artists also release downloads which are not released as singles or contained on any album. Add an extra table to your database to accommodate this extra information. [2]
 
[10] (a) (i) Explain what is meant by the term data encryption [1]
(ii) Explain in detail how encrypted data can be read by the appropriate person. [2]
(b) Many large organisations carry out disaster planning for their computer systems. Describe two elements of disaster planning which can allow an organisation to quickly recover following a disaster to their computer system. [2]
 
11. In the following question, additional credit, (up to 3 marks) will be given if your answer demonstrates skill in written communication.
Engineers have designed a new aeroplane called UltraJet that will be the biggest aeroplane ever produced. The pilots will require training before they can fly the UltraJet prototype.
The engineers have also used complex software and powerful computers to create a flight-training simulator to train UltraJet pilots.
  Explain why powerful computers are essential for flight-training simulators and describe the difficulties in producing a realistic simulator. Also describe the benefits of using flight-training simulators to train UltraJet pilots. [7+3]