Data storage and compression

Worked examples (9)

• 1The size of an image file (3 marks)
• 2The size of a text file (3 marks)
• 3The size of a mono sound file (3 marks)
• 4A stereo recording, with the minutes trap (4 marks)
• 5A photograph, answered in MiB (4 marks)
• 6The effect of changing a parameter (4 marks)
• 7A full-mark layout, end to end (5 marks)
• 8How many photographs fit on the card? (5 marks)
• 9Choosing recording settings within a size budget (6 marks)

Model answers (9)

• ✓Model answer — Paper 1 style — AO1
• ✓Model answer — Paper 1 style — AO2
• ✓Model answer — Paper 1 style — AO2
• ✓Model answer — Paper 1 style — AO2
• ✓Model answer — Paper 1 style — AO2/AO3
• ✓Model answer — Paper 1 style — AO2/AO3
• ✓Model answer — Paper 2 style — AO2
• ✓Model answer — Paper 1 style — AO2/AO3
• ✓Model answer — Paper 2 style — AO2/AO3

Worked examples (9)

• 1The three base units (3 marks)
• 2Which system is each unit on? (4 marks)
• 3Converting down the binary ladder (3 marks)
• 4Three rungs down the binary ladder (3 marks)
• 5Climbing back up, and starting from bits (4 marks)
• 6The denary ladder, and why it feels easier (4 marks)
• 7A 2 TB drive, reported in gibibytes (4 marks)
• 8Explaining the missing gigabytes (4 marks)
• 9Bits, bytes and a download time (6 marks)

Model answers (9)

• ✓Model answer — Paper 1 style — AO1
• ✓Model answer — Paper 1 style — AO1
• ✓Model answer — Paper 1 style — AO1
• ✓Model answer — Paper 1 style — AO2
• ✓Model answer — Paper 1 style — AO2
• ✓Model answer — Paper 2 style — AO2
• ✓Model answer — Paper 1 style — AO2/AO3
• ✓Model answer — Paper 1 style — AO1/AO3
• ✓Model answer — Paper 2 style — AO2/AO3

Worked examples (9)

• 1Why compress at all? (3 marks)
• 2Defining and naming the two families (4 marks)
• 3Encoding a short sequence with RLE (3 marks)
• 4Decoding and comparing the sizes (4 marks)
• 5Compressing a whole icon (5 marks)
• 6Choosing lossy or lossless for three files (4 marks)
• 7Showing that RLE can increase the file size (5 marks)
• 8Evaluating RLE for two different images (6 marks)
• 9Compression in a streaming service (6 marks)

Model answers (9)

• ✓Model answer — Paper 1 style — AO1
• ✓Model answer — Paper 1 style — AO1
• ✓Model answer — Paper 1 style — AO1
• ✓Model answer — Paper 2 style — AO2
• ✓Model answer — Paper 1 style — AO1/AO2
• ✓Model answer — Paper 2 style — AO2
• ✓Model answer — Paper 1 style — AO2/AO3
• ✓Model answer — Paper 1 style — AO3
• ✓Model answer — Paper 1 style — AO3