Past Paper Thursday 13th June 2013 - Afternoon

Question 1

State how many bytes are in a kilobyte? (1)

Answer 1

1 Kilobyte = 1024 bytes.

Question 2

State how many kilobytes are in a gigabyte? (1)

Answer 2

1 gigabyte = 1024 kilobytes.

Question 3

Describe the purpose of the ROM in a computer? (2)

Answer 3

• Stores the boot program which is used to start the computer and load the operating system.

Question 4

Describe the purpose of the RAM in a computer? (2)

Answer 4

• Stores the parts of the OS programs that are running.

- Stores the data which is currently in use for access by the CPU.

Question 5

State one difference between ROM and RAM, other than the size and the purpose? (1)

Answer 5

• ROM is non-volatile and RAM is volatile.

Question 6

A game console and a desktop computer are two different types of computer system. Describe how a game console is similar to a desktop computer, with reference to input, output and storage. (6)

Answer 6

Points may include:
• Game console has input devices,
usually specialised controllers but
also keyboards, microphones etc
similar to desktop computer
• Output is similar to desktop
computer on a screen and
speakers (sometimes using the
same standards eg HDMI, DVI)
• Game console usually has an
optical drive so that the software
to be run can be inserted. Many
also have a hard disk drive which
is the same as that used on a
desktop computer.

Question 7

State the purpose of an input device in a computer system. (1)

Answer 7

To enter data from outside the system for processing.

Question 8

State the purpose of an output device in a computer system. (1)

Answer 8

To return the results of processing

Question 9

Describe two ways that the hardware in the computer terminal can be adapted so that blind customers can use it. (4)

Answer 9

Braille keyboard/input device
• As this is a familiar entry method for blind users
• Braille print out of transaction
• so that customer can review it.
• Use loudspeakers
• To provide audio feedback of actions taken (but not when entering card
details).

Question 10

Explain why the technicians prefer to use hexidecimal. (2)

Answer 10

• it is 4 bits per hex digit / straightforward to convert

• shorter number to remember/quicker to enter/less susceptible to error.

Question 11

Display the most appropriate data type for each of these. (4)

• Song
• Length
• TimesPlayed
• Protected

Answer 11

• Song - String
• Length - Real
• TimesPlayed - Interger
• Protected - Boolean

Question 12

The mp3 player can be connected to a computer from which songs can be added. The computer has a relational database with many tables. Explain, using an example, what is meant by an entity and how entities relate to the tables. (4)

Answer 12

An entity is a type of real world object (about which data is to be stored)
• e.g. Songs/albums/singers etc
• In the relational database each entity is modelled as a table
• Instances/examples/individuals of an entity are represented by
records/rows of the table
• Entities can have attributes
• .. valid example of attributes e.g. length of song
• Attributes of an entity are represented by fields/columns of the table

Question 13

This is a computer program that simulates a 100m race. Each time the space bar is pressed the position of the player moves up by 1. When the position reaches 100, then the player has one.

CONST PlayerKey = " "
Position = 0 
REPEAT
  INPUT KeyPressed
  If KeyPressed = PlayerKey THEN
    Position = Position + 1
  END If
UNTIL Position = 100

State an example of a constant and variable in the algorithm above? (2)

Answer 13

• Constant = PlayerKey

- Variable = Position or KeyPressed

Question 14

CONST PlayerKey = " "
Position = 0 
REPEAT
  INPUT KeyPressed
  If KeyPressed = PlayerKey THEN
    Position = Position + 1
  END If
UNTIL Position = 100

State what is meant by selection and iteration using examples from the algorithm. (4)

Answer 14

Selection -
• A condition is used to decide whether code should be executed.
Example -
• Position = Position + 1 is only run if the IF condition is met.

Iteration - 
• Code is executed repeatedly.
Example -
• The code in the repeat loop will be run several times (until Position =
100).

Question 15

CONST PlayerKey = " "
Position = 0 
REPEAT
  INPUT KeyPressed
  If KeyPressed = PlayerKey THEN
    Position = Position + 1
  END If
UNTIL Position = 100

To make the game more interesting, the rules have been changed. Each time the spacebar is pressed, the postion of the player will now move up by a random number. State two changes that need to be made to include this new rule and justify. (4)

Answer 15

Point
• Position = Position + 1 should be changed
• …so the increment is a random number
Justify
• The random number should be relatively small
• …so the game remains interesting
Point
• The end condition of the loop should be changed to UNTIL Position >
100 / check if position > 100 and if so change to 100
• … as the position may not reach exactly 100 due to the random number.
Justify
• seed/initialise random number generation
• … so that numbers generated appear random

Question 16

Files are often compressed before they are sent over the internet.
- State what is meant by compression. (1)

Answer 16

Reduce the size of the file.

Question 17

State one advantage of compressing files before sending them over the internet. (1)

Answer 17

Transmits more quickly / uses less bandwidth

Question 18

State which type of compression is more useful and appropriate for downloading the source code of a large program. (3)

Answer 18

Type of compression = Lossless compression

Explanation = The code has to be exactly as it was originally written … or else it will not work.

Question 19

State which type of compression is more useful and appropriate for streaming a large video file. (3)

Answer 19

Type of compression = Lossy Compression
Explanation = Achieves higher compression/ smaller file size / faster streaming than
lossless. Video can still be viewed at lower quality (from the data compressed).

Question 20

Describe the difference between off the shelf and custom written software. (2)

Answer 20

• Off the shelf software is available for anyone to acquire and use / commercially available
• Custom written software is made especially for the school/ for a specific user

Question 21

Describe the difference between proprietary and open source software. (2)

Answer 21

• Proprietary software cannot be copied/altered (without permission of the copyright owner)
• Open source software can be modified (provided it remains open source)

Question 22

Explain the legal issues that the school should take in to account when choosing the software for ‘managing pupils’ attendance and examinations. (6)

Answer 22

Points may include:
• Must abide by software licence
• So for open source, the school
will be able to make
modifications/customisations to
exams system
• But will probably have to make
these modifications also
available to other users
• And credit all previous
contributors in the code
• Will have to purchase off the
shelf attendance package legally
• Software must be able to ensure
all legal data protection
requirements are met.

Question 23

Write an algorithm for a computer program that determines whether a triangle is an isosceles triangle.

• The user inputs the lengths of the three sides as Length 1, Length 2 and Length 3.
• If any two sides have the same length the program outputs “Isosceles”
• Otherwise the program outputs “Not Isosceles” (5)

Answer 23

Example
 INPUT Length1
 INPUT Length2
 INPUT Length3
 IF Length1 = Length2 THEN
   Output “Isosceles”
 ELSE
   IF Length1 = Length3 THEN
     Output “Isosceles”
   ELSE
     IF Length2 = Length 3 THEN
       Output “Isosceles”
     ELSE
       OUTPUT “Not Isosceles”
     END IF
   END IF
 END IF
Award marks for:
• Inputting three lengths
• Comparing lengths in pairs
• … for all three ways correctly
• … outputting “Isosceles” for all valid cases
• … outputting “Not Isosceles” for all cases and only in cases where the
three lengths are different.