CP1 Computing June 2001

1(a)

Describe one desirable feature of a programming language used in a scientific or technical application.

[1]

High precision representation of numbers which would give very accurate calculations.

(b)

Describe one desirable feature of a programming language used in a commercial application

[1]

File-handling facilities. Eg the ability to sort a file in order of a key field.

(c)

Describe one desirable feature of a programming language used in the development of web pages.

[1]

Links which, when clicked on, instructs the browser to load and display another web page.

2(a)

Explain the difference between a real number and an integer, giving an example of each data type.

[2]

a real number has a fractional part eg 12.75
an integer has no fractional part eg 12

(b)

Explain the difference between a character and a string, giving one example of each data type.

[2]

a character is a single letter, digit or punctuation mark eg 'A'
a string is a number of characters eg 'ALBERT'

(c)

Describe the kind of data which is held in a boolean data type.

[1]

data which is in two states eg TRUE or FALSE

(d)

Explain why the record is a useful data structure, giving an example.

[2]

a number of data items of different types may be included
Eg a record may consist of the following fields-
Name : string
ID_Number : integer
WeeklyWage : Real

3(a)

Many software packages include features such as mail-merge and macros.

(i)

Explain the term mail-merge, giving an example of its use.

[2]

Using a 'form letter' to produce a number of similar documents which incorporate data stored in a database.

Eg Using names and addresses stored on a database to produce letters informing customers of a new web-site.

One mark for the description and 1 mark for the example.

(ii)

Explain the term macro, giving an example of its use.

[2]

A single 'shortcut' instruction which represents a number of instructions.

Eg A macro called TITLE on a spreadsheet could perform the following instructions on a cell:

Format BOLD
Selkect font ARIAL
Set font size 14
Change text color to RED
Change background colour to YELLOW

(b)

Explain what is meant by the term data portability.

[1]

The ability to move data from one computer and use it on another computer system without any changes needing to be made.

4.(a)

A small sports club keeps a list of its members in alphabetical order of their surnames. Currently a linear search is used to find a member's name.

(i)

Name a search method which would normally be more efficient than a linear search.

[1]

a binary search

(ii)

State the advantage of this search method over a linear search and explain why it would have this advantage.

[2]

finding data is much faster
every time a record is accessed, half of the remaining records can be discounted - with a linear search, only the record accessed can be discounted.

(b)

The sports club has a shop which sells many items of sporting equipment. Data held about each item include:

a 4 digit item code
monthly sales figures for the item in the last twelve months

(i)

State the most suitable type of data structure to hold these data, using a diagram to show how it would be used.

[2]

A file of records, each record with two fields:

item_code : integer;(or string[4])
sales : array[1..12] of real;

item_ Code	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0471	£28	£56	£0	£12	£67	£42	£0	£57	£18	£12	£10	£8
1293	£41	£5	£55	£0	£0	£8	£19	£27	£0	£0	£0	£8
1366	£50	£12	£23	£24	£56	£91	£61	£22	£10	£18	£27	£30

etc...

(ii)

These data can sensibly be ordered on several different data items.
Describe one way in which they might be ordered in this case.

[1]

Each record should be stored in order of its item code.

5.(a)

A programming team often writes programs in small clearly documented sections.

(i)

Describe three advantages of writing programs in this way.

[3]

small tasks are easier to program than large ones.
it is much easier to test small programs than large ones - and if there are bugs, they can usually be found quicker.
clear documentation means changes can be made later by other programmers.

(ii)

The team also use a number of other techniques when developing software. These include the use of self-documenting identifiers and self-documenting code.

Explain each of the following terms, giving an example in each case:

self-documenting identifiers;

[2]

Variable and constant names are meaningful.
Eg use VAT_Rate instead of just V

self-documenting code.

[2]

comments are placed in the source code of the program.
Eg {This procedure calculates the VAT}

(iii)

The team use standard modules. Explain what is meant by the term standard module, and explain how the use of standard modules might help the team.

[2]

A standard module consists of a number of previously written procedures which have already been tested and which can be used in a new program.

(b)

Various types of error often occur during software development.
Describe each of the following types of error, giving an example in each case:

(i)

syntax error

[2]

not using the rules of the language properly.
Example - mis-spelling an instruction ('writln' instead of 'writeln') or missing out a compulsory semi-colon at the end of a line.

(ii)

execution error

[2]

an error which occurs when a program is run.
Example - Division by zero error.

(c)

Explain why careful version control is important when developing computer programs.

[1]

It is important that any modifications are always made to the latest version of a program.

(d)

Explain the difference between systems software and applications software, giving an example in each case.

[4]

systems software - programs which help to run and organise a computer system.
Eg : a disc formatting program
Applications software - programs which perform a certain task for the user.
Eg : a CAD package.

In a certain college course, each student submits one assignment and takes one examination.

To pass the course, the student has to achieve a certain minimum mark in both the assignment and in the examination. If either component has a very low mark, the course is failed. In all other cases the student is allowed to do a special retrieval assignment.

The following algorithm is used to output a result for each student.

Line
1	input assignment_mark;
2	input exam_mark;
3
4	if (assignment_mark >= 40 AND exam_mark >= 40) then output "Pass"
5	else if (assignment_mark < 20 OR exam_mark < 20) then output "Fail"
6	else output "Retrieval Assignment"

(i)

State what the output would be if the two inputs are:

50 and 45

[1]

Pass

70 and 18

[1]

Fail

III

38 and 38

[1]

Retrieval assignment

38 and 50

[1]

Retrieval assignment

(ii)

The word OR is correctly used in line 5 of the algorithm above. If it were replaced by the word AND, the algorithm would not produce the correct output. Give an example to show how this would happen.

[1]

Inputs : 70 and 18 would output "Retrieval assignment" when it shgould output "Fail"

7(a)

A program currently being developed uses both local and global variables.

(i)

Describe the difference between local and global variables.

[2]

A local variable may only be referred to inside the subroutine where it is declared. A global variable may be referred to anywhere in the program.

(ii)

Describe one advantage of using local variables.

The memory space is released when the procedure is completed.

(b)

The same program will need to be maintained. Describe two types of maintenance, giving an example of when it might be necessary in each case.

[4]

Corrective maintenance - to remove any bugs found in the program.
Example : The input of a certain type of data may cause the program to crash.
adaptive maintenance - when there are changes in the company.
Example : the company may open more branches and the programs may need to be adapted.

An insurance company has a call centre, where a number of sales staff answer customers' enquiries by telephone. The staff are able to access information held in a computer system.

The following diagram shows the situation described so far.

(i)

What is the name of this type of diagram?

[1]

data flow diagram

(ii)

Why are diagrams of this type particularly useful?

[1]

They show the flow of data through a system in a simple way.

(iii)

What type of object does a rounded rectangle (for instance "Make enquiry") in the above diagram represent?

[1]

A process

(iv)

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

[1]

An external entity

(v)

What type of object does an arrow (for instance "Enquiry") in the above diagram represent?

[1]

A data flow

(vi)

Give a suitable name for the object shown as X in the above diagram

[1]

Customer information

9(a)

Give two reasons why any computer system needs to be well documented.

[2]

Users of the system will need to know how to properly use the system, how to enter data etc..
If any maintenance needs doing at a later stage, then programmers will need to properly understand how the system works.

(b)

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

A systems analyst is employed to assist a small business which is trying to make its business computer systems more efficient.

The systems analyst carries out a number of tasks, including a requirements analysis, requirements specification and design. Consideration is also given to the human computer interface and the changeover.

Describe in detail the tasks undertaken by the systems analyst.

[8+3]

The systems analyst would need to investigate how the business currently operates. He would need to interview staff and management, use questionnaires or just observe who does what in the business. From this he would draw up specifications of the requirements of the new system - the essential objectives that the finished system would need to attain.

He would then design the new system. Consideration would need to be given to hardware needed, the software which would be installed, and the data which is to be stored.

The human computer interface would need to be considered. This is the way which humans will operate the hardware. Would there need to be any special hardware devices eg bar-code readers. The screen displays would also need to be designed.

Changeover can be done in several ways. The old system can be stopped and the new one started, or it may be better to introduce the new system in well-defined stages. Parallel running may take place for a while, where the old and new systems are run together for a while, the old system being stopped when it is certain that the new one works properly.