Computer Science 2210 XI Worksheet - Mock 2015 Mark Scheme.pdf

Computer Studies 2210 MARK SCHEME October 15, 2014 Worksheet

Page No. 1 of 18

Question 1 Bespoke soft ware is soft ware specifically written for a customer. It should exactly match the needs of the customer and therefore operate more efficiently for the customer’s specific requirements than generic soft ware. It is likely to be more expensive to develop and not as extensively tested. Question 2 The contents of the ‘Task’ column have been moved to match the application software.

Question 3 Any job and the associated reason from the following list.

a.

Job Reason for using robots

Assembling products

Paint spraying

Consistency and repeatability

Faster in operation than humans

Can work without breaks

Health and safety concerns

Bomb disposal

Chemical and nuclear plants

No danger to human life

Equipped with sensors (can pick up data automatically)

Vacuum cleaners/mowers

Free people’s time for leisure


Page No. 2 of 18

b. Any two points from:

writing original prose, poetry, music, etc.

creating works of art

any task where logic/rules of programming cannot be applied

one-off tasks, e.g. complex glass blowing or pottery Question 4

a. CAD can be used in architecture and in product design. b. I would expect a CAD program to be able to create 3-D drawings using vector graphics, to

rotate or walk through drawings and to calculate areas and volumes of designs. Question 5

a. Coded data is used for Type because the full description would be longer. It would take up more storage space and may lead to errors in data entry.

b. The data type for Price is real or decimal (numerical data type). c. A key field is an item of data that uniquely identifies a record. In this case, the key field is

Property. Question 6 Set Cat1, Cat2, Cat3, Cat4, Cat5 to 0 //initialisation FOR Count ← 1 TO 2000 //start main loop OUTPUT "Please enter a code between 10000 and 59999." INPUT Code //validated input WHILE (Code < 10000) OR (Code > 5999) //error detection DO OUTPUT "Out of range 10000 to 59999. Please try again." //helpful error message INPUT Code ENDWHILE CASE Code OF //CASE statement >= 50000: Cat5 ← Cat5 + 1 //test in order >= 40000: Cat4 ← Cat4 + 1 >= 30000: Cat3 ← Cat3 + 1 //increment totals >= 20000: Cat2 ← Cat2 + 1 >= 10000: Cat1 ← Cat1 + 1 ENDCASE NEXT //end main loop PRINT Cat1, Cat2, Cat3, Cat4, Cat5 //output


Page No. 3 of 18

Question 7 a. A database is a set of tables that hold information about related things. b. A file is a set of data or program items held in a named area of storage (or a physical data

structure). c. A direct access file is a file stored on disk. Its records can be accessed directly by using an

algorithm to generate a record’s disk address from the record’s key value. d. A record is a set of data items about one type of thing. e. A sequential file is a file in which records are stored in order of their record key values.

Question 8

a. The term 'validation' means examining input data to ensure that it falls within pre-set criteria. For example, a date of birth must be before a certain date to be valid for a pupil to be enrolled.

b. The term 'verification' means double-checking that copied data is correct. c. One method of verification when changing a password is to ask the user to type it a second

time, i.e. double entry. Question 9

a. Accept either of:

=C6 − B6

(C6 − B6)

b. Accept any of:

=AVERAGE(D2:D9)

=SUM(D2:D9)/8

=(D2+D3+D4+D5+D6+D7+D8+D9)/8

c. Only one possible answer: =MAX(F2:F9)

d. Accept any of:

select F2 and drag the + cursor down to F9

select F2, select copy, select F3 to F9 and select paste

select F2 to F9 and select Edit, Fill Down Question 10 Backing storage is a long-term non-volatile storage that stores programs and data for future use. Computers need backing storage so that programs and data can be stored after the power has been switched off. Question 11

a. ROM stands for ‘read-only memory’. b. RAM stands for ‘random access memory’. c. RAM is volatile storage and ROM is non-volatile storage. Data in RAM disappears when a

computer is switched off – it holds programs and data that are being worked on. Data in ROM cannot be changed after manufacture – it holds the computer’s boot information.


Page No. 4 of 18

d. Complete the following statements with ‘RAM’, ‘ROM’ or ‘backing storage’: i. Backing storage stores a copy of your work when the computer is switched off.

ii. RAM stores application programs and data while the computer is running. iii. ROM stores programs that must be available as soon as the computer is switched on.

Question 12

Error 1: line 20 Correction 1: no score should be less than 0, so Smallest should be set at a large value Error 2: line 40 Correction 2: loop does 31 iterations; should be FOR x ← 1 TO 30 Error 3: line 90 Correction 3: NEXT (line 100) automatically increments x; x ← x + 1 means that x is going up by 2 in every iteration of the loop

Question 13

a. A command line interface requires the user to type commands at a keyboard. The user needs to remember the commands (although help is usually available) and the string of options can be complex to get right. Only one command (program) at a time can be executed.

b. A graphical user interface enables the user to use a pointing device to select commands and options from menus. Several programs can be open in various windows.

Question 14


Page No. 5 of 18

Question 15 a. A buffer is an area of memory that holds data temporarily ready to be sent to a program or

peripheral device. b. A peripheral device is a device that links to the processor, such as a printer, a monitor or a

webcam. c. An interrupt is a signal from a peripheral device or a program to the processor asking for some

service (e.g. a printer may send an interrupt to ask for more data). d. Polling is a process in which the processor asks each peripheral device in turn if it needs a

service. e. Handshaking is a process in which a peripheral device and the processor (or two computers on

a network) establish communication. Question 16

A B C X

0 0 0 1

0 0 1 0

0 1 0 1

0 1 1 1

1 0 0 1

1 0 1 1

1 1 0 1

1 1 1 1

Question 17 In a batch processing system, data is processed all at once. A person does not need to interact with the computer as it is processing the data. For example, a utility-billing application is supplied with a customer database and a file of meter readings. It processes the meter readings to produce bills for the customers. Question 18

x s Result Output

1 30 50

2 6 10 10

3 60 100

4 45 75

5 60 100

6 15 25 25

7 30 50

8

9 15 25 25

10 12 20 20


Page No. 6 of 18

Question 19 A bus network has computers connected in a line. All signals are sent to all computers.

A ring network has computers connected in a circle. The signals are sent in one direction until a computer accepts them.

A star network has computers separately connected to a central hub. A switch or server directs signals to the computer they are addressed to.

Question 20

a. An intranet is a private, web-based service on a LAN. A large organisation uses it to provide information to its employees through familiar web-based tools, such as web browsers. It is used because only employees can access it.

b. An intranet is private and cannot be accessed by any member of the public, unlike the Internet which can be accessed by anyone through an ISP.


Page No. 7 of 18

Question 21 Onboard computers allow aeroplanes to operate more efficiently and safely.

a.

sensors and

ADC (if necessary) b. Any two points from:

stored flight plan

GPS repeatedly calculates position as the plane travels

repeatedly checks for significant deviations from planned course towards an intermediate or final destination

repeatedly checks for arrival at an intermediate destination (‘waypoint’)

operates in real-time

c. Any two points from:

computer can work 24/7

computer is less likely to make mistakes

computer can respond to situations more quickly

computer is less likely to misunderstand or misinterpret data

d. Any two points from:

in case computer program goes wrong

in case of computer malfunction

to maintain passenger confidence

‘unusual’ manoeuvres are best done in manual mode

in case of emergencies Question 22 The stages of the systems life cycle are:

fact finding

feasibility study

analysis

design

building and testing

documentation

implementation (changeover)

evaluation

maintenance

Question 23 a. Any three points from:

manual system requires storage for paper files

in the manual system, one branch does not know what stock is at the other branches

in the manual system, every branch needs to hold complete stock of parts


Page No. 8 of 18

computerised system reduces errors

in the computerised system, branches can share parts needed infrequently

all branches can access the same data

b. Any three points from:

observation

questionnaires

examination of documents

interviews Question 24

a. Three tasks in analysis are fact finding, creating a requirements specification and defining the flow of data through the system.

b. Programs should be tested with extreme and abnormal data, as well as normal data. c. The new system might require corrective maintenance (fixing soft ware errors or ‘bugs’),

adaptive maintenance (to reflect changes in the organisation’s requirements) or perfective maintenance (ways to improve the performance of the system).

Question 25 Four methods of system implementation are direct, phased, pilot and parallel running.

a. Direct implementation is most suitable when a system is small and not critical to business running.

b. Phased implementation is most suitable when the system can be divided into distinct phases that do not directly impact on each other.

c. Pilot implementation is most suitable when a small part of the business, such as a branch, can be operated independently from other parts.

d. Parallel running is most suitable when data is critical to the business and it can be evaluated over a short time.

Question 26

Service: VoIP or Internet telephony Associated description: no additional cost over broadband connection

Service: online banking Associated description: lower bank charges as fewer staff required; no cost of travelling to the bank

Service: online shopping, buying theatre or travel tickets Associated description: reduced cost of goods as fewer staff required; easier comparison of costs

Service: email Associated description: no postage and stationery costs

Service: teleworking Associated description: reduced transport costs (not having to go to the office)


Page No. 9 of 18

Question 27 A thermometer could be hung in the greenhouse and a humidity sensor could be stuck in the soil. Both sensors could be connected to a computer to set up an input feedback system. The computer would run a program that would test the sensor readings at regular intervals. If a reading fell outside the limits set in the soft ware, the computer would then activate an actuator. If the soil became too dry, an actuator could run a sprinkler system for a time. If the temperature was too low, the actuator would close a window or start a heater. Question 28 Robots are now used in many different situations.

a. A robot could use pressure sensors and light sensors. b. A pressure sensor could be used to ensure that the robot is touching an item before it carries

out another action. A light sensor could be used to enable the robot to navigate around a workplace.

c. Robots in factories can be used for welding, placing parts and moving objects around. d. Robots can work in places or doing jobs that would be dangerous for people. Robots can work

all day and night without breaks. Robots can accurately repeat a task many times. Question 29

a. Any two points from (other suitable changes are also acceptable):

resizing

rotating

fixing red eye

cropping b. Any one point from:

linking to a file

importing from a file

dragging and dropping onto a slide

c. Any one item from:

animations

sound

videos Question 30

a. A computer simulation is a model of the data in a real-world situation. A small business could store its accounts on a spreadsheet and create a simulation of its future performance under different conditions.

b. A computer simulation makes it easier and cheaper to try out alternative scenarios to arrive at the best solution to a problem.


Page No. 10 of 18

Question 31 a. Video-conferencing means using both video and audio feeds over a network to connect people

in a virtual ‘meeting’. b. Hardware needed for video-conferencing includes webcams and microphones. c. Advantages of video-conferencing are that meetings can be held at short notice and people do

not have to spend time travelling. Question 32

a. Any two points from:

possible loss of jobs or redeployment

need to re-train or de-skilling

loss of social interaction [2]


reduced costs (fewer staff and less office space)

standard responses to common queries

24/7 customer service

ability to advertise new services and products

flexibility in staff deployment [2]


queries answered at any time of day

diagrams and manuals available

faster response time (no problem with busy phone)

less expensive (phone calls can be costly)

consistent advice Question 33

a. Soft ware copyright is similar to copyright in a book – it guarantees that the author or developer of the work is the person legally entitled to get commercial benefit from it. Define the term ‘computer virus’.

b. A computer virus is a piece of program code within a data or program file that copies itself and ‘infects’ other files in the same or another host computer.

c. De-skilling is the loss of skills due to using a computerised process to replace a worker with specific training and skills.

Question 34

a. Teleworking is a method of working in which an employee works from home or a remote office using telecommunication links. They may also connect to the employer’s network.

b. A teleworker needs a computer, a telephone, a broadband connection (i.e. access to the internet) and networking soft ware. Some might also need the tools required for video conferencing.

c. Advantages of teleworking are that an employer does not need to supply buildings and furniture for its entire staff.


Page No. 11 of 18

d. Advantages of teleworking are that an employee does not spend time and money travelling to work and that work can oft en be fitted around other commitments.

Question 35

a. Any two problems and associated protections. To get full marks [4] you have to supply 2 problems (1 mark each) and 2 associated protections, 1 for each problem (1 mark each):

Problem Protection

Virus Use anti-virus software

Hacking Firewall, anti-hacking software, passwords

Access from outside the surgery Restrict access to known computers

b. Any one explanation from:

password use

hierarchy of user IDs (different groups for doctors and administrative staff)

use of dongle

c. Any one device from:

CD or DVD drive

(flash) memory stick

external (portable) hard disk drive Question 36 The principles on which data protection legislation is based are:

Personal data may only be obtained and processed fairly, lawfully and for specified purposes.

Data must be accurate, kept up-to-date, sufficient, relevant, not excessive and deleted when no longer needed.

Individuals have a right of access to the data held about them and to have factually incorrect information corrected.

Data must be protected from corruption, loss and access by or disclosure to people who are not authorised to see them.

Data must not be transferred to another country unless that country provides a similar level of legal protection for personal data.

Question 37

a) “10100” b) “10101” c) re-reading the byte that was sent

request that the byte is resent


Page No. 12 of 18

Question 38 a. The output is: 4, 3, 8. b. An algorithm written as a subroutine (procedure) and stored in a program library can be re-

used by other programs. The program can call the subroutine from the library file by temporarily passing control to it.

Question 39

a. Any two points from:

weather stations collect data using sensors

satellites send information remotely

aircraft pilots send data


compares historic data ...

... with new data

creates patterns from historic data

calculates statistical probability of likely path of hurricane


hurricane path superimposed on a map

graph showing speed of wind and direction of travel

animation showing the movement of the hurricane over time Question 40

a) Interrupt b) MAC address c) Handshaking d) IP address e) Buffer

Question 41

a. The algorithm inputs a sequence of numbers and keeps a record of the largest number read so far. Once the loop ends, it outputs the largest number input.

b. Any value less than 0 stops the loop and outputs the answer. c.


Page No. 13 of 18

Question 42 a.

b.

Question 43

Device 1: a microwave oven Reason: only simple input is expected – keypad on front of device Device 2: a washing machine Reason: only one set of tasks to perform

Question 44


Page No. 14 of 18

Question 45

Question 46 Y = 0: N = 0: K = 0: S = 0 for count = 1 to 50 000

input number X = number/100 000 000 if X > 0.7 then S = S + 1

else if X > 0.6 then K = K + 1 else if X > 0.5 then N = N + 1

else if X > 0.4 then Y = Y + 1 else print “error in number”

next count print Y, N, K, S Question 47

a. sequence of colours is: blue green white

time delay is: 7 seconds

b.

c.

sequence always starts from left to right

so sequence would still be red, blue then green


Page No. 15 of 18

Question 48 a.

(i) Working = (4 × 6) + (2 × 5) + (1 × 4) + (9 × 3) + (2 × 2) + (3 × 1) = 24 + 10 + 4 + 27 + 4 + 3 = 72 ÷ 11 = 6 remainder 6 valid/not valid: NOT valid

(ii) Working = (8 × 6) + (2 × 5) + (0 × 4) + (1 × 3) + (5 × 2) + (6 × 1) = 48 + 10 + 0 + 3 + 10 + 6 = 77 ÷ 11 = 7 remainder 0 valid/not valid: VALID

b. Working

= (5 × 6) + (0 × 5) + (2 × 4) + (4 × 3) + (1 × 2) = 30 + 0 + 8 + 12 + 2 = 52 need to add 3 to make the total 55 (i.e. exactly divisible by 11)

Check digit: 3


Page No. 16 of 18

Question 49 PENDOWN LEFT 90 REPEAT 3 FORWARD 30 RIGHT 90 ------------------------------------------------------------------------------------------- ENDREPEAT FORWARD 10 LEFT 90 OR PENUP ------------------------------------------------------------------------------------------- PENUP OR LEFT 90 FORWARD 10 PENDOWN ------------------------------------------------------------------------------------------- REPEAT 2 OR REPEAT 3 FORWARD 20 ------------------------------------------------------------------------------------------- RIGHT 90 ENDREPEAT FORWARD 20 OR (LEFT/RIGHT 180) (LEFT 90) ONE mark for each correct group of statements Alternative answer for last groups FORWARD 20 RIGHT 90 ------------------------------------------------------------------------------------------- FORWARD 20 RIGHT 90 FORWARD 20 Question 50

count = 0 while count < 5001 input house if house > 50 000 then tax = house * 0.01

else if house > 100 000 then tax = house * 0.015 else if house > 200 000 then tax = house * 0.02

else tax = 0 print tax count = count + 1 endwhile


Page No. 17 of 18

Question 51

a.

simple project

not a complex problem with many tasks

few inter task dependencies

timescale is more obvious

Gantt charts are easier to understand/PERT charts can be confusing

production of PERT charts can be expensive

PERT charts can be complicated to manage

b. Up to three points from I.

Questionnaire for parents

asks standard questions

so results can be analysed easily/quickly

no need for analyst to be present

parents can complete at a time convenient to them

(parents) can remain anonymous

incentives to return questionnaire

inexpensive/more efficient method for large groups (of parents)

Up to three points from

interviewing for school office staff

allows questions to be tailored to the individual

can ask for clarification

staff may tell you things that you haven’t identified as issues II.

observation

document search Question 52 repeat input start_point input end_point input number cost = (end_point – start_point) * number * 2

if number >= 3 then cost = cost – (cost/10) } input money change = money – cost

for x = 1 to number print ticket

next x output change until no more customers


Page No. 18 of 18

Question 53

a) CLI description – user communicates by typing in commands (in response to a prompt) – several commands are entered to carry out a task (such as loading software) CLI hardware – keyboard – keypad GUI description – user interacts with a computer using pictures and symbols (icons)/drop-down menu – tasks are initiated by selecting the icon – usually part of a windows/wimp environment GUI hardware – pointing device (e.g. mouse) – touch screen

b) saving/collecting data with no actual need for human interaction

c)

Documents

Computer Science 2210 XI Worksheet - Mock 2015 Mark Scheme.pdf