Calculating File Sizes (Cambridge International IGCSE Computer Science)
Exam board Cambridge International · IGCSEUpdated 2024-05-13
Spec point —
1.3.2· "2 Calculate the file size of an image file and a sound file, using information given"
Calculating File Sizes
How do you calculate the size of a bitmap image?
-
Calculating the size of a bitmap image can be carried out with either of the following formulas:
- Resolution x colour depth
- Image width x image height x colour depth
Example
| Image Files |
|---|
| (Resolution) x (Colour Depth) |
| | Size of bitmap image = | | | |---|---|---| | Resolution | 250,000 | Resolution = width x height | | Colour Depth | 24 bits (3 bytes) | 24 bits = 3 bytes | | 250,000 x 24 | = (bit to bytes) /8 (bytes to KiB) /1024 | 6,000,000 bits 750,000 bytes Final answer: 732 KiB | | 250000 x 3 | = (bytes to KiB) /1024 | 750,000 bytes Final answer: 732 KiB | |
OR
| Image Files |
|---|
| (Image width) x (Image height) x (Colour Depth) |
| | Size of bitmap image = | | | |---|---|---| | Image width | 500 | | | Image height | 500 | | | Colour Depth | 24 bits | 24 bits = 3 bytes | | (500 x 500 x 24) | = (bit to bytes) /8 (bytes to KiB) /1024 | 6,000,000 bits 750,000 bytes Final answer: 732 KiB | | (500 x 500 x 3) | = (bytes to KiB) /1024 | 750,000 bytes Final answer: 732 KiB | |
How do you calculate the size of a sound file?
-
Calculating the size of a sound file is carried out with the following formula:
- Sample rate x duration x sample resolution
Example
| Sound Files |
|---|
| (Sample Rate) x (Duration in seconds) **x **(Sample Resolution) |
| | Size of sound file = | | | |---|---|---| | Sample rate | 100 | Samples per second | | Duration | 60 | Seconds | | Sample resolution | 24 | Number of bits stored per sample | | 100 x 60 x 24 | = (bit to bytes) /8 (bytes to KiB) /1024 | 144,000 bits 18,000 bytes 18 KiB | |
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