Group 2 File Compression

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File Compression


File compression allows users to send large files by reducing the amount of bits and bytes in a file. This allows for the file to be transferred faster over slower internet connections. Once this compressed file is downloaded, a program like winzip or stuffit expand back to its original state.



How does it do it?

Most compressed files are made up of redundant, having the same information listed over and over again. File compression simply gets rid of the redundancy. File compression list the information once and then refers back whenever it reappears.

for example : In JFK's inaugural address he said this famous line. " Ask not what your country can do for you, ask what you can do for your country." In this quote we see that there are words repeated like; your, country, ask, what, can, do, for and you Most compression programs use a adaptive dictionary based on algorithm to shrink files. So our dictionary will read. 1. ask 2. what 3. your 4. country 5. can 6. for 7. you

Types of zip files

.ZIP , .RAR TAR.GZ .TGZ

How to UN compress compressed files

To uncompress files one must use the appropriate program that matches the type of zip file compressed although one can use 7-zip which is free and supports all major compressed file formats

FACTS

  • Zip files compress data therefore save time and space
  • Makes downloading software and transferring email attachments faster
  • Good for Distributing files on the internet
  • Saves disc space
  • If you compress a file, you may end up with a bigger file during compression. If the file is already compressed
  • Lossy lose size and quality and loss less you lose less quality and space.
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