Zip files compression
![zip files compression zip files compression](https://www.codeproject.com/KB/files/359758/C__Users_sean.OFFICE_Desktop_Holding_Ground_UZipDotNetSubmission_files_image007.png)
- Zip files compression zip file#
- Zip files compression update#
- Zip files compression archive#
- Zip files compression software#
- Zip files compression code#
Zip is a lossless compression format: after decompression, the data is identical to what it was before compression. This allowed others to study the format and create programs that create, extract, or otherwise interact with Zip files in a compatible way. One aspect that most likely contributed to the Zip format's success was that PKZip came with a document, the Application Note, which explained exactly how the format works. Katz's program for creating such files was called PKZip, and it was soon adopted by the BBS and PC world.
Zip files compression software#
Further, the filename extension of ".ZIP", first used in connection with data compression software on the first release of this software, is also hereby dedicated to the public domain, with the fervent and sincere hope that it will not be attempted to be appropriated by anyone else for their exclusive use, but rather that it will be used to refer to data compression and librarying software in general, of a class or type which creates files having a format generally compatible with this software. The file format of the files created by these programs, which file format is original with the first release of this software, is hereby dedicated to the public domain.
Zip files compression archive#
Moving on from Arc, in 1989 Katz created a new archive format which he named Zip and dedicated to the public domain: In the end, the case was settled to SEA's advantage. The dispute and the surrounding debate in the BBS and PC world became known as the Arc Wars. They sued for trademark violation and copyright infringement. SEA, however, were not thrilled by Katz's initiative. Photo of Phil Katz from an article in the Milwaukee Sentinel on 19 September 1994. According to legend, much of the work took place at his mother Hildegard's kitchen table in Glendale, Wisconsin. The program became popular, and Katz quit his job and founded PKWare to focus on developing it. It was compatible with SEA's Arc, but faster due to routines written in assembly, and it had a new compression method added by Katz. In the late eighties, a programmer named Phil Katz released his own Arc program, PKArc. One such archiver that was popular with the BBS scene was Arc, written by Thom Henderson of System Enhancement Associates (SEA), a small company he had founded with his brother-in-law. An archiver stores one or more files into a single file, an archive, allowing the files to be stored or transferred as a single unit, and ideally also compresses them to save storage space and transfer time. One important tool for making file sharing easier was the archiver. Table of Contentsīack in the eighties and early nineties, before the Internet became widely available, home computer enthusiasts used dial-up modems to connect to Bulletin Board Systems (BBSes) over the telephone network.Ī BBS is an interactive computer system that typically allows users to send messages, play games, and share files.Īll that was needed to go online was a computer, a modem, and the phone number of a good BBS-something that could be found in lists published by computer magazines, and on other BBSes. This made Deflate compression more than twice as fast as the previous version.
Zip files compression update#
Update : In hwzip-1.3.zip, the minimum Lempel–Ziv back reference length was increased from three to four bytes, and the hash was changed from a three-byte rolling hash to a four-byte multiplicative hash. It also ensures that Deflate blocks always emit at least two non-zero dist codeword lengths, for compatibility with old zlib versions. Update : In hwzip-1.4.zip, the distance2dist table was split into two smaller tables, reducing the binary size by 32 KB. Update : I wrote a follow-up article about the legacy Zip compression methods: Shrink, Reduce, and Implode. Who provided valuable feedback on draft versions of this material. If you find any issues, please let me know. I have done my best to provide a bug-free implementation.
Zip files compression code#
The source code is available in hwzip-2.0.zip. It tells some of the history, and provides a reasonably efficient example implementation written from scratch in C.
Zip files compression zip file#
This article explains how the Zip file format and its compression scheme work in great detail: LZ77 compression, Huffman coding, Deflate and all.
![zip files compression zip files compression](https://www.win-rar.com/uploads/pics/open-zip-file_08.png)
Hopefully it is interesting to read about too. The implementation turned into an exciting programming exercise there is great pleasure to be had from creating a well oiled machine that takes data apart, jumbles its bits into a more efficient representation, and puts it all back together again.
![zip files compression zip files compression](https://icdn.digitaltrends.com/image/digitaltrends/how-to-zip-1-500x500.jpg)
At some point I decided to address that by learning how it works and writing my own Zip program. I have been curious about data compression and the Zip file format in particular for a long time.