中文（繁體）
中文（简体）
English
S4 ICT: Data Representation and File Size (Paper 1 (basics))
Tutor Prep Guide · Bits and bytes, the 1024 based KB, MB and GB scale, binary and hexadecimal conversion, ASCII characters, image resolution and colour depth, sound sampling rate and bit depth, video and compression, plus the usual mistakes in file size calculation
S4 ICT: Data Representation and File Size (Paper 1 (basics))
Paper 1 (basics): ten questions on data representation and file size, with answers and notes.
Direct answers Level: S4 ICT; format: byte conversion, binary and hexadecimal, image and sound file size, compression and unit errors.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: S4 ICT: Data Representation and File Size |
| Level | S4 |
02 Questions (10 items)
- FoundationHow many bytes are there in 8 bits?
- FoundationHow many KB are there in 1024 bytes?
- FoundationEach ASCII character takes 1 byte. How large is a text file of 100 characters?
- IntermediateHow many KB are there in 5 MB?
- IntermediateWhat is the binary number 1011 in denary?
- IntermediateWrite the denary number 13 as a 4-bit binary number.
- ChallengeAn uncompressed 800 by 600 pixel image uses 1 bit per pixel. How many bytes does it take?
- ChallengeHow many bits are there in 3 KB?
- ChallengeAn image must show 256 colours. What is the minimum colour depth per pixel?
- Error redoError clinic: a student answered that 1 KB equals 1000 bytes. What is the correct value?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 1 byte | One byte is made of eight bits, so 8 bits is exactly 1 byte. |
| 2 | 1 KB | The KB scale is based on 1024, so 1024 bytes divided by 1024 gives 1 KB. |
| 3 | 100 bytes | One byte per character means 100 characters take 100 bytes, before line break characters. |
| 4 | 5120 KB | One MB is 1024 KB, so 5 times 1024 gives 5120 KB. |
| 5 | 11 | Taking the place values gives 1×8 plus 0x4 plus 1×2 plus 1×1, which is 11. |
| 6 | 1101 | 13 is 8 plus 4 plus 1, so the four bit pattern is 1101. |
| 7 | 60 000 bytes | 800 times 600 gives 480 000 bits, and dividing by 8 gives 60 000 bytes. |
| 8 | 24 576 bits | 3 times 1024 gives 3072 bytes, and multiplying by 8 gives 24 576 bits. |
| 9 | 8 bits | Two to the power of eight is 256, so each pixel needs 8 bits, which is exactly 1 byte. |
| 10 | 1 KB = 1024 bytes | Computers work in binary and 1024 is two to the power of ten, while 1000 is only the drive maker advertising scale. |
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.
Write down the conversion factors first (1 byte = 8 bits, 1 KB = 1024 bytes), then multiply the number of pixels or samples by the bits per unit, and only at the end divide by 8.Tutor 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.
© TutorZone · www.tutorzone.com.hk · For personal study and teaching use only.