iGCSE Computer Science: Data Compression and Encryption

Which of these are recognised types of file compression? (select all that apply)

• lossless

• lossy

• superchannel

• standard

• redundant

What are the main reasons to compress data? (select all that apply)

• To reduce secondary storage space

• To maximise the available RAM memory

• To speed up network transmission times

• To optimise the data

• To reduce packet congestion on networks

Which of these are recognised lossless compression algorithms? (select all that apply)

• RLE

• LZ-77 (dictionary coder)

• Caesar cipher

• Merges sort

What is the correct Run-length encoding for the data: cccmmmmmsssssdcccccc

• 3c5m5s1d6c

• c3m5s5d1c6

• cmsdc35516

• cccmmmmmsssssdcccccc

Which of these image file formats support lossless compression techniques? (select all that apply)

• JPG

• PNG

• GIF

• BMP

• SVG

Which of these audio file formats support lossy compression?

• FLAC

• MP3

• WAV

• OggPCM

• WMA

What is the correct order of memory storage units from smallest to largest?

• KiB MB MiB GB TiB

• KiB MiB MB TiB GB

• MB MiB KB GB TiB

• KB GB MB MiB TiB

What is the name of the lossy compression algorithm used in JPG image compression?

• Discrete Cosine Transform

• Abstract Sinusoidal Mutation

• Run-length encoding

• LZ-77

On which of these data strings would you expect a dictionary-based lossless compression algorithm like LZ-77 to achieve the highest compression ratio?

• This is an endless loop. This is an endless loop. This is an endless loop. This is an endless loop. This is an endless loop. This is an endless loop. This is an endless loop. This is an endless loop.

• lpumf yxidt mgcwo aiyfj nqyuj znhja vjacx vewcf jmxgy suqwj dvnzq zcops gpsbz rgxox sxypw mvvun cxxda dfixa burli sitbh ljprx uqehk aggap btnep ispxx zmuus ndbyd hwplq zbwgd pznkr zkdbp ssedo

• Grumpy wizards make toxic brew for the evil Queen and Jack

• Old MacDonald had a farm

  E-I-E-I-O

  And on his farm he had a cow

  E-I-E-I-O

  With a moo-moo here

  And a moo-moo there

  Here a moo, there a moo

  Everywhere a moo-moo

  Old MacDonald had a farm

  E-I-E-I-O

On which piece of data would you expect the run-length encoding algorithm to achieve the highest compression ratio?

• Nellie the Elephant packed her trunk

  And said goodbye to the circus

  Off she went with a trumpety-trump

  Trump, trump, trump

• Computer Science is great Computer Science is great Computer Science is great Computer Science is great Computer Science is great Computer Science is great Computer Science is great

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