These were taken from the 2008 Section 1.
1a(i)Describe how bit-mapped images are stored. 1 KU
- An array/grid of pixels
- Each dot/pixel has a binary value
- Each pixel stored as a bit/byte/binary value/black=1 & white=0
- Accept black=1 and white=0 type answer but not the colour of each pixel
- Any one from above 1 mark (Not “the colour of pixels are stored” or “individual pixels” or “pixel by pixel”)
1a(ii) Describe how vector images are stored. 1 KU
- As a number/list of objects (each of which has attributes defining the objects)
- Objects are defined by attributes/mathematical description
- Accept an example object used to describe eg rectangle and attributes
- Any other valid
- 1 mark for any of the above
1b Is the above image bit-mapped or vector? Justify your answer.2 PS
- Bit-mapped (1 mark)
- Composed of grid of (individual) pixels
- Does not contain/is not comprised of (collection of discrete) objects
- It is pixelated
- It is a photograph/taken with a digital camera
- 1 mark for any valid bullet point (Not painting or resized)
2a Explain how the heuristic detection technique is used to detect a virus.1 KU
- It looks for a suspicious pattern of behaviour (which was previously associated with a virus)
- Accept use of a valid example to illustrate concept
- Any other valid
- 1 mark
2b Explain why a trojan horse is not classified as a computer virus. 1 PS
- A trojan horse is not self replicating
- Does not infect other files
- 1 mark for any one of the above (do not accept a description of what a trojan horse does)
