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Lempel–Ziv–Stac
Lempel–Ziv–Stac (LZS, or Stac compression or Stacker compression) is a lossless data compression algorithm that uses a combination of the LZ77 sliding-window compression algorithm and fixed Huffman coding. It was originally developed by Stac Electronics for tape compression, and subsequently adapted for hard disk compression and sold as the Stacker disk compression software. It was later specified as a compression algorithm for various network protocols. LZS is specified in the Cisco IOS stack. Standards LZS compression is standardized as an INCITS (previously ANSI) standard. LZS compression is specified for various Internet protocols: * – ''PPP LZS-DCP Compression Protocol (LZS-DCP)'' * – ''PPP Stac LZS Compression Protocol'' * – ''IP Payload Compression Using LZS'' * – ''Transport Layer Security (TLS) Protocol Compression Using Lempel-Ziv-Stac (LZS)'' Algorithm LZS compression and decompression uses an LZ77 type algorithm. It uses the last 2 KB of unc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LZ77
LZ77 and LZ78 are the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978. They are also known as LZ1 and LZ2 respectively. These two algorithms form the basis for many variations including LZW, LZSS, LZMA and others. Besides their academic influence, these algorithms formed the basis of several ubiquitous compression schemes, including GIF and the DEFLATE algorithm used in PNG and ZIP. They are both theoretically dictionary coders. LZ77 maintains a sliding window during compression. This was later shown to be equivalent to the ''explicit dictionary'' constructed by LZ78—however, they are only equivalent when the entire data is intended to be decompressed. Since LZ77 encodes and decodes from a sliding window over previously seen characters, decompression must always start at the beginning of the input. Conceptually, LZ78 decompression could allow random access to the input if the entire dictionary were known in ad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stac Electronics
Stac Electronics, originally incorporated as State of the Art Consulting and later shortened to Stac, Inc., was a technology company founded in 1983. It is known primarily for its Lempel–Ziv–Stac lossless compression algorithm and Stacker disk compression utility for compressing data for storage. History The original founders included five Caltech graduate students in Computer Science (Gary Clow, Doug Whiting, John Tanner, Mike Schuster and William Dally), two engineers from the industry (Scott Karns and Robert Monsour) and two board members from the industry (Robert Johnson of Southern California Ventures and Hugh Ness of Scientific Atlanta). The first employee was Bruce Behymer, a Caltech undergraduate in Engineering and Applied Science. Originally headquartered in Pasadena, California and later in Carlsbad, California, the company received venture capital funding to pursue a business plan as a fabless chip company selling application-specific standard products to the ta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stacker (disk Compression)
Stac Electronics, originally incorporated as State of the Art Consulting and later shortened to Stac, Inc., was a technology company founded in 1983. It is known primarily for its Lempel–Ziv–Stac lossless compression algorithm and Stacker disk compression utility for compressing data for storage. History The original founders included five Caltech graduate students in Computer Science (Gary Clow, Doug Whiting, John Tanner, Mike Schuster and William Dally), two engineers from the industry (Scott Karns and Robert Monsour) and two board members from the industry (Robert Johnson of Southern California Ventures and Hugh Ness of Scientific Atlanta). The first employee was Bruce Behymer, a Caltech undergraduate in Engineering and Applied Science. Originally headquartered in Pasadena, California and later in Carlsbad, California, the company received venture capital funding to pursue a business plan as a fabless chip company selling application-specific standard products to the ta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hifn
Hifn (styled ''Hi/fn'') was a semiconductor manufacturer founded in Carlsbad, California, in 1996 as a corporate spin-off from Stac Electronics. The company was later headquartered in Los Gatos, California, and had offices in North America, Europe and Asia. It designed and sold security processors. It was acquired by Exar Corporation in 2009. History 1996-2008: Founding and early years Hifn was founded in 1996 as a spin-out of the semiconductor company Stac, Inc. It held its initial public offering in December 1998. The company's stock was traded on the NASDAQ under the symbol HIFN. In 1998, Hifn became the first company to offer a processor with integrated encryption and compression, following this in 1999 with the fastest security processor for VPNs. In 2000, Hifn announced an "Intelligent Packet Processor": a security co-processor capable of not only performing raw algorithm processing, but also modifying the complete packet, allowing their processors to transform an IP ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MS-DOS 6
MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few operating systems attempting to be compatible with MS-DOS, are sometimes referred to as "DOS" (which is also the generic acronym for disk operating system). MS-DOS was the main operating system for IBM PC compatibles during the 1980s, from which point it was gradually superseded by operating systems offering a graphical user interface (GUI), in various generations of the graphical Microsoft Windows operating system. IBM licensed and re-released it in 1981 as PC DOS 1.0 for use in its PCs. Although MS-DOS and PC DOS were initially developed in parallel by Microsoft and IBM, the two products diverged after twelve years, in 1993, with recognizable differences in compatibility, syntax, and capabilities. Beginning in 1988 with DR-DOS, Co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microsoft Point-to-Point Compression
Microsoft Point-to-Point Compression (MPPC; described in RFC 2118) is a streaming data compression algorithm based on an implementation of Lempel–Ziv using a sliding window buffer. According to Hifn's IP statement, MPPC was patent-encumbered (last US patent granted on 1996-07-02). Where V.44 or V.42bis operate at layer 1 on the OSI model, MPPC operates on layer 2, giving it a significant advantage in terms of computing resources available to it. The dialup modem's in-built compression (V.44 or V.42bis) can only occur after the data has been serially transmitted to the modem, typically at a maximum rate of 115,200 bit/s. MPPC, as it is controlled by the operating system, can receive as much data as it wishes to compress, before forwarding it on to the modem. The modem's hardware must not delay data too much, while waiting for more to compress in one packet, otherwise an unacceptable latency level will result. It also cannot afford to, as this would require both sizable computing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lossless Data Compression
Lossless compression is a class of data compression that allows the original data to be perfectly reconstructed from the compressed data with no loss of information. Lossless compression is possible because most real-world data exhibits statistical redundancy. By contrast, lossy compression permits reconstruction only of an approximation of the original data, though usually with greatly improved compression rates (and therefore reduced media sizes). By operation of the pigeonhole principle, no lossless compression algorithm can efficiently compress all possible data. For this reason, many different algorithms exist that are designed either with a specific type of input data in mind or with specific assumptions about what kinds of redundancy the uncompressed data are likely to contain. Therefore, compression ratios tend to be stronger on human- and machine-readable documents and code in comparison to entropic binary data (random bytes). Lossless data compression is used in many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Algorithm
In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specifications for performing calculations and data processing. More advanced algorithms can perform automated deductions (referred to as automated reasoning) and use mathematical and logical tests to divert the code execution through various routes (referred to as automated decision-making). Using human characteristics as descriptors of machines in metaphorical ways was already practiced by Alan Turing with terms such as "memory", "search" and "stimulus". In contrast, a Heuristic (computer science), heuristic is an approach to problem solving that may not be fully specified or may not guarantee correct or optimal results, especially in problem domains where there is no well-defined correct or optimal result. As an effective method, an algorithm ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Huffman Coding
In computer science and information theory, a Huffman code is a particular type of optimal prefix code that is commonly used for lossless data compression. The process of finding or using such a code proceeds by means of Huffman coding, an algorithm developed by David A. Huffman while he was a Sc.D. student at MIT, and published in the 1952 paper "A Method for the Construction of Minimum-Redundancy Codes". The output from Huffman's algorithm can be viewed as a variable-length code table for encoding a source symbol (such as a character in a file). The algorithm derives this table from the estimated probability or frequency of occurrence (''weight'') for each possible value of the source symbol. As in other entropy encoding methods, more common symbols are generally represented using fewer bits than less common symbols. Huffman's method can be efficiently implemented, finding a code in time linear to the number of input weights if these weights are sorted. However, although opt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hard Disk Compression
A disk compression software utility increases the amount of information that can be stored on a hard disk drive of given size. Unlike a file compression utility, which compresses only specified files—and which requires the user to designate the files to be compressed—an on-the-fly disk compression utility works automatically through resident software without the user needing to be aware of its existence. On-the-fly disk compression is therefore also known as transparent, real-time or online disk compression. When information needs to be stored to the hard disk, the utility compresses the information. When information needs to be read, the utility decompresses the information. A disk compression utility overrides the standard operating system routines. Since all software applications access the hard disk using these routines, they continue to work after disk compression has been installed. Disk compression utilities were popular especially in the early 1990s, when micro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cisco IOS
The Internetworking Operating System (IOS) is a family of proprietary network operating systems used on several router and network switch models manufactured by Cisco Systems. The system is a package of routing, switching, internetworking, and telecommunications functions integrated into a multitasking operating system. Although the IOS code base includes a cooperative multitasking kernel, most IOS features have been ported to other kernels, such as Linux and QNX, for use in Cisco products. Not all Cisco networking products run IOS. Exceptions include some Cisco Catalyst switches, which run IOS XE, and Cisco ASR routers, which run either IOS XE or IOS XR; both are Linux-based operating systems. For data center environments, Cisco Nexus switches (Ethernet) and Cisco MDS switches ( Fibre Channel) both run Cisco NX-OS, also a Linux-based operating system. History The IOS network operating system was created from code written by William Yeager at Stanford University, which w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
