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ocr gcse computing

JUNE 2015
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OCR GCSE Computing June 2015  exam paper can be downloaded here



OCR GCSE Computing June 2015  mark scheme can be downloaded here

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1 Answer
  • Input device: touch screen / microphone / accelerometer/(hardware) button/ camera / (hard) keyboard
  • Output device: screen / speaker / vibrating device / LEDs
  • Storage device: Solid state memory e.g. SD card, memory card, flash memory , SIM card

More help here - Input/Output/Storage devices
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2A answer
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More help here - more file types
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2b answer
When the file is compressed some detail/data/quality/resolution is lost...
 ... which is not noticeable in the video file/video still viewable with lower quality
 … but would make the text file unreadable/lose meaning or comprehension

More help here - Lossy vs lossless
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3a answer
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More help here - Data types

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3b answer
  • (Age < 20 is FALSE so) Dose = 2
  • ( Gender = “Female” is FALSE) so Dose = Dose * 0.5
  • ... therefore Dose = 1
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3c answer
  • (Age is less than 20 = true) so Dose = 0.1 * Age
  • 1.9
  • [ isPregnant AND Dose > 1.5 ] is TRUE
  • Dose = 1.5
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4a answer
  1. antivirus
  2. firewall

More help here - Security utility programs
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4b answer
e.g.
(User name and) password
Only allows you to use the system if you are authorised

Encryption
Prevents hackers from understanding any data if accessed (e.g. passwords)

Access rights
To prevent files from being modified/deleted

User access control
Prevents users from making changes to the system

Marks in pairs

More help here - OS security
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5ai answer
 High level code :
  • human oriented code / written by programmers
  • contains words for commands / closer to English/natural language
  • Machine independent /Portable to different systems
  • Needs to be translated before it can be executed.
  • Problem based
  • One (high level) command equates to many machine code instructions.
Machine code:
  • Code for the CPU to execute / not readily understandable by humans
  • binary instructions
  • specific to a particular (type of) computer / not portable to different systems
  • does not need to be translated
[max 2 marks for each type of code]

More help here - HLL and machine code
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5aii answer

  • To translate the high level code into machine code
  • To pick up (syntax) errors

More help here -  Compiler
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5b answer
Examples of standards;
  • Code should be written using standard/agreed conventions
  • ... such as in the choice/capitalisation of variable names
  • …language chosen
  • ..use of functions
  • ..comments
  • Meaningful identifiers
  • Indenting (constructs)
Examples of justification
  • … compatibility between components
  • ..consistency
  • …allow multiple people to work on the same project
  • …ensure coding conventions are kept
  • …so others can read/edit the code
​
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6a answer
Software that is produced for a variety of users / not for a specific user / commercially available to anyone / immediately available

More help here - Off the shelf

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6b answer
  • Create tables / entities
  • Define fields / attributes / columns
  • Define (primary) keys
  • Define relationships / links between tables / foreign keys
  • Set the constraints on the data /validation rules / data types / field lengths / other suitable example

More help here -  Database explained
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6c answer
e.g.
  • Add client/appointment data
  • Edit client/appointment data
  • Delete client/appointment data
  • Run/Create/View reports using a relevant example of a report that would be needed e.g. today’s appointments
  • Search/query for data using a relevant e.g. search for a client’s phone number
  • Back up (client/appointment) data.
  • Archive (client/appointment) data/ example of archiving

More help here - Why use a databse
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7a answer
  • Instructions/programs(currently running)/data are stored in the RAM...
  • these are fetched from the RAM by the CPU /Processor
  • ... where the instructions are executed / instructions are processed / data is processed

More help here:
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7b answer
  • To store instructions/data that is frequently used / previously used / next to be used
  • Data does not need to be fetched from RAM
  • Speeds up access


More help here - Cache memory explained
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7c answer
E.g.
Memory;
  • Smaller in size
  • Faster access
  • Larger capacity
  • More durable
  • Costs less per byte/kb etc
Technology can;
  • be smaller
  • be more mobile/portable
  • have similar capacity
 
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8ai answer
  • (Part of the instruction which) specifies the operation to be carried out
  • e.g. 00001000 = add to timer/00000100 = subtract from timer
​

More help here - Opcode explained
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8aii answer
  • (Part of the instruction which) supplies the data/ address/value needed for an operation
  • e.g. the number to be added/subtracted from the timer / numerical example from the table (00010100 or 00000001)

More help here - Operand explained
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8b answer
00000101 00011110
1 mark per byte​

More help here - Denary to binary
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8c answer
  • Instructions and data are fetched at different points of the fetch execute cycle
  • Instructions and data are kept in separate parts of the memory (by the operating system)

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9a answer
e.g.
  • record log on / log off times
  • remote access / view users’ screens
  • audit printing
  • keylogging
  • monitor internet usage / downloads
  • monitoring emails / files sent / copied
  • inspect files in users’ areas

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9b answer
IP addresses can be changed / are allocated as needed
MAC addresses can’t be changed / every device has a fixed MC address

IP(v4) addresses are 4 bytes long
MAC addresses are 6 bytes long

IP(v4) addresses are normally written in denary
MAC addresses are normally written in Hex

IP addresses are configured by software
MAC addresses are configured in hardware

IP addresses are used for routing across a WAN/internet
MAC addresses are only used within the LAN

​[marks in pairs, maximum 2 pairs]

More help here - IP address
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9c answer
  • Redundant components/hardware/capacity (servers/disks/routers etc) is built into the network
  • If there is a failure, network automatically switches to use the spare capacity
  • Allows the bank to continue to operate / avoids network downtime
  • avoiding loss of income /customer dissatisfaction/ loss of records / other example related to the bank

More help here - failover
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10a answer
Lidia​


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10b answer
  • Program finds there is no position 7 in the array / array index out of bounds
  • An error will occur / an error message would be displayed / program will crash

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10c answer
Example:

INPUT Num
For i = 1 to Num
    Temp = PlayerName(6)
    PlayerName(6) = PlayerName(5)
    PlayerName(5) = PlayerName(4)
    PlayerName(4) = PlayerName(3)
    PlayerName(3) = PlayerName(2)
    PlayerName(2) = PlayerName(1)
    PlayerName(1) = Temp
Next i

Award marks for:
  • Input the number of places to move (e.g. Num)
  • Use of temporary variable(s) or second array to avoid overwriting values in the array
  • Sensible use of a loop
  • ... with correct end condition
  • Correctly deals with moving from position 1 (e.g. 1 + Num)
  • Correctly deals with moving from position 6 (e.g. Num )

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      • Run length encoding
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      • Stored program concept
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      • Hex
      • Data Representation
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      • What is a computer
      • How does a computer work
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          • While loop challenges
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          • String slicing challenges
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        • Algorithms
        • Programming paradigms
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        • Analysis and design of algorithms
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      • 01 - Particles >
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        • Particles
      • 02 - Cells >
        • Microscope introduced
        • Looking at cells
        • Specialised cells
        • Unicellular organisms
      • 03 - Energy >
        • Energy introduced
        • Energy transfers
        • Conduction, Convection, Insulators
      • 04 - Chemical ideas & reactions >
        • Periodic table
        • Chemical reactions
        • Chemical reactions2
      • 05 - Light and Sound >
        • Light introduced
        • The Eye
        • Colours and filters
        • Waves and Sound
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