中文（繁體）
中文（简体）
English
S4 ICT Data Representation, Paper 3: carries, prefixes and pixel bits
S4 ICT Data Representation, Paper 3: carries, prefixes and pixel bits
Paper 3 covers binary 10110 as 22, denary 58 as 00111010, hex B7 as 183, five bytes as 40 bits, 2 GiB as 2147483648 bytes, an ASCII gap of 7, 1111 plus 0001 giving 10000, denary 255 as FF and a 24-bit pixel with 256 levels per channel.
Reminders Each hex digit holds 4 bits, Ki and Mi and Gi each multiply by 1024, and upper and lower case ASCII are 32 apart.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 25 |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: S4 ICT: Data Representation |
| Level | S4 |
02 Questions (10 items)
- FoundationWhat is the denary value of the binary number 10110?
- FoundationWhat is denary 58 in 8-bit binary?
- FoundationWhat is the denary value of the hexadecimal number B7?
- FoundationHow many bits are there in 5 bytes?
- IntermediateHow many bytes are there in 2 GiB?
- IntermediateLower-case a has ASCII code 97 and upper-case Z has 90. What is the difference?
- IntermediateAdd binary 1111 and 0001. What is the binary result?
- ChallengeWhat is denary 255 in hexadecimal?
- ChallengeA pixel stores red, green and blue with 8 bits each. How many levels per channel and how many bits per pixel?
- Error redoError repair: a student said 1 KiB equals 1000 bytes. What is correct?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 22 | Sixteen plus four plus two is 22, and the zero bit contributes nothing. |
| 2 | 00111010 | 58 is 32 plus 16 plus 8 plus 2, and the remaining bits are zero. |
| 3 | 183 | B stands for 11, and 11 times 16 is 176, plus 7 gives 183. |
| 4 | 40 bits | Each byte is 8 bits, so five bytes are 5 times 8, which is 40 bits. |
| 5 | 2147483648 bytes | Gi is 1024 cubed, which is 1073741824, and doubling it gives 2147483648 bytes. |
| 6 | 7 | Ninety-seven minus ninety is 7, while the upper and lower case blocks are 32 apart. |
| 7 | 10000 | Fifteen plus one is 16, written as 10000, so four bits carry into a fifth. |
| 8 | FF | 255 divided by 16 is 15 remainder 15, and both fifteens are written F. |
| 9 | 256 levels each, 24 bits per pixel | Eight bits give 2 to the power 8, which is 256 levels, and three channels make 24 bits. |
| 10 | 1 KiB is 1024 bytes | Ki is a binary prefix meaning 2 to the power 10, which is 1024, while 1000 belongs to the decimal k. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
Book an S4 ICT tutorTutor Registration →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.
