O-LevelComputer ScienceData Transmission2210/11 · May/June 2020 · Q38 Marks
Carla's computer has a USB port. Carla uses the USB port to connect her mobile device to her computer, to transfer her photos.
- (a)Give three benefits of using a USB port to connect the mobile device to the computer. Benefit 1 Benefit 2 Benefit 3[3]
- (b)State the type of data transmission used when transferring data using a USB port.[1]
- (c)Carla wants to reduce the file size of the photos she has transferred to her computer. She does not want the quality of the photos to be reduced, so she uses lossless compression. Describe how lossless compression reduces the file size of the photos.[4]
Mark scheme
Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.
- [3] 3(a) Any three from: It is a universal standard; It can't be inserted the wrong way around; Supports different transmission speeds; Automatically detects if correct driver installed; It will charge the mobile device at the same time
- [1] 3(b) Serial
- [4] 3(c) A compression algorithm is used; No data is removed in the compression process; An index/dictionary of pixels is created; The number of times a pixel is repeated in a row is stored
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