Huffman Compression

Also known as Huffman encoding, an algorithm for the lossless compression of files based on the frequency of occurrence of a symbol in the file that is being compressed. The Huffman algorithm is based on statistical coding, which means that the probability of a symbol has a direct bearing on the length of its representation. The more probable the occurrence of a symbol is, the shorter will be its bit-size representation. In any file, certain characters are used more than others. Using binary representation, the number of bits required to represent each character depends upon the number of characters that have to be represented. Using one bit we can represent two characters, i.e., 0 represents the first character and 1 represents the second character. Using two bits we can represent four characters, and so on.

Unlike ASCII code, which is a fixed-length code using seven bits per character, Huffman compression is a variable-length coding system that assigns smaller codes for more frequently used characters and larger codes for less frequently used characters in order to reduce the size of files being compressed and transferred.

For example, in a file with the following data:

XXXXXXYYYYZZ

the frequency of “X” is 6, the frequency of “Y” is 4, and the frequency of “Z” is 2. If each character is represented using a fixed-length code of two bits, then the number of bits required to store this file would be 24, i.e., (2 x 6) + (2x 4) + (2x 2) = 24.

If the above data were compressed using Huffman compression, the more frequently occurring numbers would be represented by smaller bits, such as:

X by the code 0 (1 bit)
Y by the code 10 (2 bits)
Z by the code 11 (2 bits)

therefore the size of the file becomes 18, i.e., (1x 6) + (2 x 4) + (2 x 2) = 18.

In the above example, more frequently occurring characters are assigned smaller codes, resulting in a smaller number of bits in the final compressed file.

Huffman compression was named after its discoverer, David Huffman.

Webopedia Staff
Webopedia Staff
Since 1995, more than 100 tech experts and researchers have kept Webopedia’s definitions, articles, and study guides up to date. For more information on current editorial staff, please visit our About page.

Top Articles

List of Windows Operating System Versions & History [In Order]

The Windows operating system (Windows OS) refers to a family of operating systems developed by Microsoft Corporation. We look at the history of Windows...

How to Create a Website Shortcut on Your Desktop

Website Shortcut on Your Desktop reviewed by Web Webster   This Webopedia guide will show you how to create a website shortcut on your desktop using...

What are the Five Generations of Computers? (1st to 5th)

Reviewed by Web Webster Each generation of computer has brought significant advances in speed and power to computing tasks. Learn about each of the...

Hotmail [Outlook] Email Accounts

Launched in 1996, Hotmail was one of the first public webmail services that could be accessed from any web browser. At its peak in...

Capacity Planning

Capacity planning is a process that helps organizations determine the resources needed to...

Defense Advanced Research Projects...

The Defense Advanced Research Projects Agency (DARPA) is a research and development agency...

XiaoBa Ransomware

XiaoBa is a type of file-encrypting ransomware that runs on Windows and encodes...