CP1 Computing January 2003

1.(a)

Describe what is meant by each of the following terms, giving one example in each case:

(i)

syntax error;

[2]

an error in using the rules of the language.
Eg - a spelling mistake - PRUNT instead of PRINT

(ii)

logical error.

[2]

an error in the algorithm. The program runs but does not perform the task correctly.
Eg - performing instructions in the wrong order, or executing a loop the wrong number of times.

(b)

Give one reason why it is usually easy to discover a syntax error.

[1]

The program will not run. The compiler will usually find it at compile-time and indicate the sort of syntax error it is with a diagnostic error message.

2(a)

An integrated package contains word processing and spreadsheet facilities. Two features of the integrated package are editing capabilities and mail-merge.

(i)

Give an example to show how editing capabilities could be used.

[1]

data from the spreadsheet could be copied and pasted into a word processed document and altered if necessary.

(ii)

Using an example, show how a mail-merge operation could link the word processing and spreadsheet facilities together.

[2]

documents may be produced using a form letter prepared on the word processor but incorporating data from the spreadsheet (which may be different for each printed document).

(iii)

Describe one advantage of having a programming facility within the package.

[1]

complex procedures involving various items of data may be programmed and used, then saved and used whenever required at a later date.

(b)

The developers of this integrated package have tried to ensure that it has a well-designed and "user-friendly" human-computer interface (HCI).

Describe three features of a well-designed HCI

[3]

meaningful icons which run commonly needed processes. (eg printing)
easy to use by those with low IT skills.
easy to understand 'Help' facilities.

3(a)

A linear search is used to search for one particular number in a large set of ordered numbers.

(i)

Name an alternative search method which will usually find the number more quickly than a linear search.

[1]

binary search

(ii)

Explain how this alternative search works, using a diagram if you so wish.

[3]

the middle number of the set is checked against the search number. If it is not equal to it...
if the middle number is less than the search key then the first half of the set is discarded....otherwise the second half of the set is discarded.
this process is continued, halving the size of the set, until the search number is found.

(b)

State a circumstance in which the linear search is the most suitable method.

[1]

when the set of numbers is not sorted into order.

4(a)(i)

Give an example of some data which could be conveniently stored in a record, but which could not be stored in a two-dimensional array.

[1]

pupils' names, forms and exam marks for an IT exam.

(ii)

Explain why the data could not be stored in a two-dimensional array.

[1]

the data is not all of the same type. Some are text (names) and some are numbers (exam marks).

(b)

Give an example of some data which could conveniently be stored in a two-dimensional array.

[2]

the exam marks for a number of pupils and a number of different exams. (All the data are numbers)

5(a)

A certain programming language has excellent record-handling and file-handling capabilities. What type of application might this language be suitable for?

[1]

commercial application.

(b)

Another programming language handles complex calculations very well. What type of application might this language be suitable for?

[1]

scientific application

(c)

Another programming language allows different fonts and layouts to be used and allows access by a number of browsers. What is the main use of this type of language?

[1]

creating and editing web pages.

In each case, name a suitable data type for the storage of the following data:

(i)

a person's surname, for example Evans

[1]

text (character string)

(ii)

the first initial of a person's name, for example J

[1]

character

(iii)

a person's age in complete years, for example 27

[1]

integer

(iv)

a person's height in metres, for example 1.62

[1]

real number

(v)

whether a person is left-handed, for example TRUE

[1]

boolean

7(a)

The term rogue value is often used in connection with data input to a computer program. State an application which could use a rogue value and give an example of a set of data for this application, clearly indicating the rogue value.

[2]

Inputting exam marks in order to calculate the average.
56, 67, 45, 89, 39, -1
The rogue vale is -1

(b)

Explain what is meant by the scope of a variable in a computer program.

[1]

The amount of the program where a variable exists and can be referenced. Some variables are local to a subroutine and some are global, and can be used throughout the program.

A software house is developing a computer system to handle emergency calls to a city's ambulance service. The software development team uses various methods to ensure that the software is of very high quality.

(i)

Why is it very important that this computer system is of very high quality?

[1]

If the software fails, there could be loss of life.

(ii)

I Explain what is meant by self-documenting code.

[1]

program code which includes comments explaining what variables are and the way the program works.

II Give one reason why the development team might use self-documenting code.

[1]

it is easier for members of the team who did not code the program to understand it and to make changes if necessary.

(iii)

Give three reasons why the development team might use standard modules.

[3]

useful subroutines may be stored and used in a number of programs without re-writing them every time.
they should work as they would already have been tested.
program development will be quicker as time is not needed to re-code subroutines from these modules.

(iv)

Explain why careful version control is important.

[1]

it is important that changes are always made to the latest version otherwise previous changes may be lost.

A specialist car dealer supplies classic cars to its customers. The dealer finds suitable cars by searching a national database.

The situation is shown in the diagram below:

(i)

Write down the name for this type of diagram.

[1]

data flow diagram

(ii)

What type of object does a shadow rectangle (for instance Customer in the above diagram) represent?

[1]

an external entity

(iii)

What type of object does a rounded rectangle (for instance Check availability in the above diagram) represent?

[1]

a process

(iv)

Give a suitable name for the object shown as A in the diagram.

[1]

details of customer request

(v)

Give a suitable name for the object shown as B in the diagram.

[1]

details of car

(vi)

Give a suitable name for the object shown as C in the diagram.

[1]

car availability

10.

A sophisticated burglar alarm in an art gallery has a backup electricity supply which normally starts working within a second or two of the main electricity supply failing.

The burglar alarm rings a loud bell if an intruder is detected inside the building. Since security is of great importance, the alarm also sounds if the main electricity supply fails and is not restored within five seconds. (You may assume that the bell itself has its own unbreakable electricity supply.)

Inputs to the control system are:

intruder
This will be TRUE if an intruder has been detected. It will be FALSE otherwise.

main-electricity-supply
This will be TRUE if there is a main electricity supply. It will be FALSE otherwise.

time-since-main-electricity-failed
If the main electricity supply has failed, this will be the number of seconds since this happened. It will be zero otherwise.

The algorithm used is shown below.

Statement

1	input intruder
2	input main-electricity-supply
3	input time-since-main-electricity-failed
4
5	if ((intruder = TRUE) OR ((mail-electricity-supply = FALSE) AND (time-since-main-electricity-failed > 5)))
6	then sound alarm

(a)

State what will happen when the three inputs are:

	intruder	main-electricity-supply	time-since-main-electricity-failed
(i)	TRUE	TRUE	0
(ii)	FALSE	FALSE	2
(iii)	FALSE	FALSE	6

[3]

the alarm will sound
there will be no alarm
the alarm will sound

(b)

The burglar alarm would fail to work correctly if the word AND in statement 5 was replaced with the word OR. Describe what would go wrong.

[1]

the alarm would sound as soon as the electricity supply went off, even if there was no intruder.

11.

In the following question, additional credit (up to 3 marks) will be given if your answer demonstrates skill in written communication.

Apex Bikes sells a large range of bicycles, from children's bicycles to professional racing bicycles. Apex sells bicycles from the shop and also orders them for customers. Currently, the shop does not use a computerised system. Apex's owner would like to introduce a computer system to show customers what is available and also for ordering bicycles from suppliers.

Imagine you are employed as a systems analyst by the owner of Apex. Five steps you will need to carry out are the requirements analysis, the requirements specification, the design of the new system, the selection of suitable hardware and the selection of suitable software.

Describe in detail how you would carry out the five steps shown in italics in the above paragraph.

[8 +3]

The requirements analysis will involve investigating how the present system works in the shop in order to find out what the main problems are. The investigation will involve spending some time observing operations in the shop, and may involve interviews with the staff or questionnaires which I will ask them to fill in.

The requirement specifications can then be produced. This will be a list of the objectives which the new system must meet, and what it needs to be able to do. There may also be criteria suggested by which the success of the new system can be measured.

The new system can then be designed. The design will be subject to restraints that the management of the shop may impose - these may involve financial limits or time limits when the new system must be installed by.

Selection of suitable hardware will involve the selection of the computers, any networking as well as specialist peripherals which may be needed such as bar-code readers.

Software will also need to be selected for installing on the computers. These programs may be bought from software suppliers, or written and coded by programmers to the specifications which the shop needs.