O-LevelComputer ScienceData Representation2210/12 · Oct/Nov 2018 · Q111 Marks
Computers use a character set to convert text into binary. One character set that can be used is ASCII. Each letter in ASCII can also be represented as a denary value.
- (a)The word BUS has the denary values: B U S 66 85 83 Convert the denary values into 8-bit binary. 66 85 83[3]
- (b)(i)Each letter in ASCII can also be represented as a hexadecimal value. The word KEY has the 8-bit binary values: K E Y 01001011 01000101 01011001 Convert the three 8-bit binary values into hexadecimal. 01001011 01000101 01011001[3]
- (b)(ii)Give three other uses of hexadecimal notation in computer science. 1 2 3[3]
- (b)(iii)State two benefits of using hexadecimal notation to represent binary values. Benefit 1 Benefit 2[2]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.
- [1] 1 mark for each correct 8-bit binary number
- 66 01000010
- 85 01010101
- 83 01010011
- [1] 1 mark for each correct hexadecimal number
- 4B
- 45
- 59
- [3] Three from:
- ∞ (HTML) colour codes
- ∞ Error messages
- ∞ MAC addresses
- ∞ IP addresses
- ∞ Assembly language
- ∞ Memory dump
- ∞ Locations in memory
- [2] Two from:
- ∞ Easier to read/write/understand (for humans)
- ∞ Easier to remember (for humans)
- ∞ Short way to represent binary // Uses less screen/display space
- ∞ Fewer errors made (in data transcription)
- ∞ Easier to debug (for humans)
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