CP1 Computing June 2006

[1]

It is important that the Human-Computer Interface (HCI) of any computer system is well designed.
Give two reasons why this is important.

[2]

if the design is poor then users will find it unattractive and difficult to use, and they will buy and use other systems instead.
if the interface is not designed to be appropriate for the level of the user's IT skills then they will be unable to use it or find it difficult..

[2](a)

A program contains an error where a command word is accidentally left out.

(i)

What is the name for this type of error?

[1]

syntax error

(ii)

Give another example of this type of error, other than where a command word is left out.

[1]

an incorrectly spelled instruction Eg PRUNT instead of PRINT

(b)

The following statement is a part of another program:

FinalValue = Input1 / Input2

(i)

State a circumstance under which this statement could contain a logical error.

[1]

If the FinalValue is the product of Input1 and Input2, then this would be a logical error (dividing instead of multiplying)

(ii)

State a circumstance which will cause an execution error when this statement is executed.

[1]

If Input2 is zero.

(c)

Errors are often located and resolved during program maintenance.

(i)

What is the name of the type of maintenance where errors are located and resolved?

[1]

Corrective maintenance.

(ii)

Explain what is meant by the term perfective maintenance, giving one example where it might be necessary.

[2]

Adjusting the system to make it operate better.
For example, an application that searches for data may be adapted to run the search faster.

(iii)

Name and describe one other type of maintenance.

[2]

Adaptive maintenance.
This involves making changes to the system to suit the changes of the business that uses it.

[3](a)

Documentation is particularly useful to a programmer who wishes to make changes to an existing computer program. Give two reasons why good documentation is important in this case.

[2]

The programmer needs to understand the way a program works if he is going to effectively make changes without causing errors.
If the programmer can easily identify sections of a program he will know which sections of code to change.

(b)

State one other type of documentation.

[1]

user documentation.

[4]

A local council is researching the use of public transport and how this use is affected by weather conditions. A certain bus is timetabled to leave the town bus station daily at 8:15 am. Each day, researchers note the number of passengers on the bus as it leaves, together with the temperature and other data.

(i)

What data type would be most suitable for storing the number of passengers?

[1]

integer

(ii)

What data type would be most suitable for storing the temperature.

[1]

real

(iii)

Name an item of data from this research which would most sensibly be stored in a boolean data type.

[1]

Whether it is raining when the bus leaves the bus station (YES or NO)

(iv)

Each month,, all this data is keyed into a computer system for analysis. A rogue value is used during the input of the passenger number data.

Describe the purpose of a rogue value and suggest a value for it in this case.

[2]

The rogue value indicates that the end of the input data has been reached.
Input -1 for the number of passengers.

[5]

A firm stores data about its customer accounts on its computer system in a particular order.

(i)

What name is given to the process in which data items are put into order?

[1]

sorting

(ii)

Why might it be useful to the firm to store the data in order.

[1]

searching for data is faster because fast search algorithms such as binary search can be used.

[6]

A mobile phone company employs people to sell phone contracts to members of the public in the street. Sales data for each salesperson each month are recorded as shown below:

Staff Code	Sales data for each month Number of phone contracts sold
	Jan	Feb	Mar	Apr	May	...
1	256	210	185	...	...	...
2	317	297	324	...	...	...
3	...	...	...	...	...	...
...	...	...	...	...	...	...

(i)

What is the full name for this type of data structure?

[1]

two-dimensional array.

(ii)

State the circumstances under which it would be better to store data in a record, rather than in the above data structure. Give an example of data (related to the phone company staff) which should be stored in a record.

[2]

If the data are of different data types, then a record is more suitable.
Staff Code (integer); Name (string); Date of Birth (Date); Total sales this year (integer).

[7]

It is often necessary to choose whether to develop an application using a programming language or using a software package.

(i)

There are various types of programming languages, for instance high-level and low-level languages. Explain the difference between high-level and low-level languages.

[2]

high-level languages use instructions that are close to the language the programmer speaks (Eg English)
low-level languages use instructions closely related to the machine code instructions that a computer can execute.

(ii)

Not all high-level languages are designed for the same purpose. Give an example of an application which might sensibly use programs written in a scientific language.

[1]

an engineering program used to design bridges, and calculates the stress at various places.

(iii)

If the decision is made to develop the application using a software package, extensive use may be made of macros and data portability.

Giving an example in each case, explain what is meant by:

(I)

a macro;

[2]

a single instruction that represents a pre-defined sequence of instructions.
Example - running a macro could execute a sequence of instructions that set up a template for a number of word processed documents.

(II)

data portability.

[2]

data from one application can be transferred and used in another one.
Example - data from a database can be imported into a spreadsheet.

(iv)

State one advantage that the use of a software package is likely to have over the use of a programming language.

[1]

the application would be developed faster.

[8]

NanniesDirect is an agency which helps parents in a certain town to find a suitable person to look after their children. People who wish to work as nannies can apply to NanniesDirect, who check on a national register of nannies before interviewing the person. If all is satisfactory, the person's name is added to NanniesDirect's own register.

The diagram below illustrates the situation described.

(i)

What name is given to this type of diagram?

[1]

a data flow diagram

(ii)

What type of object does the open box represent?

[1]

a data store

(iii)

Draw the shape used in the diagram to represent an external entity?

[1]

(a shadowed rectangle)

(iv)

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

[1]

Nanny's application.

(v)

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

[1]

Result of check.

(vi)

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

[1]

Interview the person

(vii)

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

[1]

NanniesDirect's Register

[9]

Lliwedd College runs a one-year course for students consisting of six modules. At the end of the course students are awarded a Distinction, a Merit or a Pass, or they may fail.

The algorithm used is shown below:

Statement
1	input ModulesPassed
2	input MeanMark
3	if (ModulesPassed = 6 AND MeanMark >= 70)
4	then output "Distinction"
5	else if (ModulesPassed = 6 AND MeanMark >= 60)
6	then output "Merit"
7	else if (ModulesPassed >= 5 AND MeanMark >= 50)
8	then output "Pass"
9	else output "Fail"

(i)(I)

Write down the output for a student who passes 6 modules with a mean mark of 66.

[1]

"Merit"

(II)

Write down the output for a student who passes 4 modules with a mean mark of 66.

[1]

"Fail"

(III)

Write down the output for a student who passes 5 modules with a mean mark of 54.

[1]

"Pass"

(IV)

Write down the output for a student who passes 6 modules with a mean mark of 72.

[1]

"Distinction"

(ii)

The algorithm above is correct. Assume now that it is incorrectly copied so that the word "else" is omitted from statement 7 as shown below.

7	if (ModulesPassed >= 5 AND MeanMark >= 50)

(I)

Write down all the output which the incorrect algorithm will give for a student who passes 6 modules with a mean mark of 66.

[1]

"Merit"
"Pass"

(II)

Write down all the output which the incorrect algorithm will give for a student who passes 4 modules with a mean mark of 66.

[1]

"Fail"

[10]

Describe in detail how a binary search works, using a diagram if you wish.

[3]

A binary search is used to access a record key in a sorted list of record keys.
The middle key is compared to the search key. If it is equal...then the key is found. If the search key is less than the middle key, the top half of the list is discarded....otherwise the bottom half of the list is discarded.
This process is repeated, halving the size of the list each time, until the search key is found.

[11]

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

A software house has been asked to develop a complex suite of programs for a bank.

Before writing the program, it is necessary to carry out a requirements analysis and produce a requirements specification. The programmers then intend to use a top-down design method, and use standard modules where possible.

Describe in detail what is meant by the terms requirements analysis and requirements specification and give a detailed explanation why the software house might choose to use a top-down design method and standard modules.

[9+3]

A requirements analysis is an investigation into the current problems that the bank may be having and what the bank needs the new suite of programs to do. This can be done by interviewing the managers or staff that work in the bank, by using questionnaires and analysing the results, by observing the current practices or by reading existing documentation.

The requirements specification would report on what the programs would need to do - what data would need to be input, what data processing needs to be carried out and what outputs are required. If there is a database used, then the structure and format of the data would also need to be specified. A budget and time plan may also be included.

A top-down design method would break a large task into successively smaller tasks. Small tasks are easier to develop, test and debug than large programs and would speed up the process of writing the programs.

Standard modules are previously written subroutines that can be used in the new programs. These have already been tested and should work reliably in the new programs. Using previously written subroutines would speed up the process of program development and mean fewer errors.