Boost your exam performance with our top-notch Computer Science Revision Notes, meticulously compiled from official mark schemes of past papers. These concise, exam-focused notes cover all topics in 1.3 (How data is exchanged between different systems) of the A Level OCR specification.
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1.3 - How data is exchanged
between different systems
,Compression
Compression: The process of making a file smaller / take up less storage.
Why use compression?
• Reduces download times so it’s faster to stream
• Reduces data usage so saves money
,Lossy compression
Lossy: Reduces file size by permanently removing data. This means that
the file cannot be decompressed to restore its original quality.
- Not suitable for text files because
+ More effective at reducing file size
permanently removing some data will
compared to lossless
make it unreadable
+ Suitable for images & videos because
- The loss of quality on a video may be
the loss of quality is unlikely to be
noticeable if it’s being streamed on a
noticeable
slow connection
, Lossless compression
Lossless: Reduces file size by rewriting the data in a more efficient format,
while still preserving the original data. This means that the file can be
decompressed to restore its original quality.
+ Suitable for text files because the - Less effective at reducing file size
original data is preserved compared to lossy
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