How is data compressed?

We all compress data using softwares like WinZip and WinRar.

How it is done by these softwares?

How come the size of the file we pack, gets reduced?

Replies

  • Sahithi Pallavi
    Sahithi Pallavi
    Even I dont know? Me too waiting for the answer.
  • Pechu
    Pechu
    Its simple.

    The compression is due to the algorithms we perform on the file, mostly cryptographic algorithms. eg: run length encoding, more...

    take a file with text inside, lots of words occur twice, thrice or lot of times. The repeated words are removed and their count and location are remembered(which takes less space than the words in separate). Later which decompressing, the words are restored.

    You can also see the compression simply by doing the following.

    1. Take a image file of size around 1-5mb.
    2. Insert the image into MS Word.
    3. Save the word file.
    4. Now check the size of the word file. 😀 it will be less than the size of the image because, MS Word has a compression algorithm.



    Like ways lots of algorithms are present for compression.
    " The more we compress, the more time it takes to decompress "



    Some useful links.

    1. #-Link-Snipped-#
    2. Data Compression Applications
  • gaurav.bhorkar
    gaurav.bhorkar
    Thanks for the information, Pechu.

    Useful links indeed.
  • lal
    lal
    ya, i didin't know that.
  • skipper
    skipper
    Compressing files is about redundant codes. What counts as redundant depends on the file.
    Check out what MPEG and JPEG compression is about--the discrete Hadamard transform.
  • kunalonly
    kunalonly
    the compress of data is done by the link list and stack .
    we have the fixed length and variable type of record
    in that algorithm that is the use of the stack and link list
    use for data compress by using the stack and link list algorithm

    thank you
  • mickyald
    mickyald
    it's purely mathematical. for text some compression techniques use directory method like lz77,lz78 and for images and video complex algorithm are use some compressions technologies are mpeg,H.263, H.261, huffman compression etc.
  • Maitham.k
    Maitham.k
    yes it is pure mathematics and there are two type of compression: loss-less type simply for regular data and data return as it was, and lossy type for sound mostly and videos, data when decompressed is not the same as it was.

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