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Gzip
gzip is a file format and a software application used for file compression and decompression. The program was created by Jean-loup Gailly and Mark Adler as a free software replacement for the compress program used in early Unix systems, and intended for use by GNU (from where the "g" of gzip is derived). Version 0.1 was first publicly released on 31 October 1992, and version 1.0 followed in February 1993. The decompression of the ''gzip'' format can be implemented as a streaming algorithm, an important feature for Web protocols, data interchange and ETL (in standard pipes) applications. File format gzip is based on the DEFLATE algorithm, which is a combination of LZ77 and Huffman coding. DEFLATE was intended as a replacement for LZW and other patent-encumbered data compression algorithms which, at the time, limited the usability of compress and other popular archivers. "gzip" is often also used to refer to the gzip file format, which is: * a 10-byte header, cont ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HTTP Compression
HTTP compression is a capability that can be built into web servers and web clients to improve transfer speed and bandwidth utilization. HTTP data is compressed before it is sent from the server: compliant browsers will announce what methods are supported to the server before downloading the correct format; browsers that do not support compliant compression method will download uncompressed data. The most common compression schemes include gzip and Brotli; a full list of available schemes is maintained by the IANA. There are two different ways compression can be done in HTTP. At a lower level, a Transfer-Encoding header field may indicate the payload of an HTTP message is compressed. At a higher level, a Content-Encoding header field may indicate that a resource being transferred, cached, or otherwise referenced is compressed. Compression using Content-Encoding is more widely supported than Transfer-Encoding, and some browsers do not advertise support for Transfer-Encoding co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tar (file Format)
In computing, tar is a computer software utility for collecting many files into one archive file, often referred to as a tarball, for distribution or backup purposes. The name is derived from "tape archive", as it was originally developed to write data to sequential I/O devices with no file system of their own. The archive data sets created by tar contain various file system parameters, such as name, timestamps, ownership, file-access permissions, and directory organization. POSIX abandoned ''tar'' in favor of '' pax'', yet ''tar'' sees continued widespread use. History The command-line utility was first introduced in the Version 7 Unix in January 1979, replacing the tp program (which in turn replaced "tap"). The file structure to store this information was standardized in POSIX.1-1988 and later POSIX.1-2001, and became a format supported by most modern file archiving systems. The tar command was abandoned in POSIX.1-2001 in favor of pax command, which was to support ust ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compress
compress is a Unix shell compression program based on the LZW compression algorithm. Compared to more modern compression utilities such as gzip and bzip2, compress performs faster and with less memory usage, at the cost of a significantly lower compression ratio. The uncompress utility will restore files to their original state after they have been compressed using the ''compress'' utility. If no files are specified, the standard input will be uncompressed to the standard output. In the upcoming POSIX and Single Unix Specification revision, it is planned that DEFLATE algorithm used in gzip format be supported in those utilities. Description of program Files compressed by ''compress'' are typically given the extension ".Z" (modeled after the earlier pack program which used the extension ".z"). Most ''tar'' programs will pipe their data through ''compress'' when given the command line option "-Z". (The ''tar'' program in its own does not compress; it just stores multipl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mark Adler
Mark Adler (born 1959) is an American software engineer. He is best known for his work in the field of data compression as the author of the Adler-32 checksum function, and a co-author together with Jean-loup Gailly of the zlib compression library and gzip. He has contributed to Info-ZIP, and has participated in developing the Portable Network Graphics (PNG) image format. Adler was also the Spirit Cruise Mission Manager for the Mars Exploration Rover mission. Early life and education Adler was born in Miami, Florida and raised as the only child of David and Bertha Adler. Adler earned his Bachelor of Science in mathematics and Master of Science in electrical engineering degrees from the University of Florida in 1981 and 1985, respectively. In 1990, Adler earned his Ph.D. in physics from the California Institute of Technology. Career Post-doctoral After his doctorate, Adler worked for Hughes Aircraft in their Space and Communications Group, working on diverse projects includ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jean-loup Gailly
Jean-loup Gailly (born 1956) is a French computer scientist and an author of gzip. He wrote the compression code of the portable archiver of the Info-ZIP and the tools compatible with the PKZIP archiver for MS-DOS. He worked over zlib in collaboration with Mark Adler. He prefers to write his hyphenated first name with only the J but not the L capitalized. He wrote a chapter on fractal image compression for Mark Nelson's The Data Compression Book. From 1990 to 1995, while working for Chorus Systèmes SA, he designed the real-time executive of the ChorusOS microkernel. From 1999 to 2001, he was the CTO of Mandrakesoft. From 2006 to 2014, he worked at Google as a Tech. Lead Manager. References External links Jean-loup's home pageJean-loup Gailly on gzip, Go and Mandrake an interview on Slashdot ''Slashdot'' (sometimes abbreviated as ''/.'') is a social news website that originally advertised itself as "News for Nerds. Stuff that Matters". It features news s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inferno (operating System)
Inferno is a distributed operating system started at Bell Labs and now developed and maintained by Vita Nuova Holdings as free software under the MIT License. Inferno was based on the experience gained with Plan 9 from Bell Labs, and the further research of Bell Labs into operating systems, languages, on-the-fly compilers, graphics, security, networking and portability. The name of the operating system, many of its associated programs, and that of the current company, were inspired by Dante Alighieri's ''Divine Comedy''. In Italian, ''Inferno'' means "hell", of which there are nine circles in Dante's ''Divine Comedy''. Design principles Inferno was created in 1995 by members of Bell Labs' Computer Science Research division to bring ideas derived from their previous operating system, Plan 9 from Bell Labs, to a wider range of devices and networks. Inferno is a distributed operating system based on three basic principles: * Resources as files: all resources are represented as fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concatenation
In formal language theory and computer programming, string concatenation is the operation of joining character strings end-to-end. For example, the concatenation of "snow" and "ball" is "snowball". In certain formalisations of concatenation theory, also called string theory, string concatenation is a primitive notion. Syntax In many programming languages, string concatenation is a binary infix operator. The + (plus) operator is often overloaded to denote concatenation for string arguments: "Hello, " + "World" has the value "Hello, World". In other languages there is a separate operator, particularly to specify implicit type conversion to string, as opposed to more complicated behavior for generic plus. Examples include . in Edinburgh IMP, Perl, and PHP, .. in Lua, and & in Ada, AppleScript, and Visual Basic. Other syntax exists, like , , in PL/I and Oracle Database SQL. In a few languages, notably C, C++, and Python, there is string literal concatenation, mea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclic Redundancy Check
A cyclic redundancy check (CRC) is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to digital data. Blocks of data entering these systems get a short ''check value'' attached, based on the remainder of a polynomial division of their contents. On retrieval, the calculation is repeated and, in the event the check values do not match, corrective action can be taken against data corruption. CRCs can be used for error correction (see bitfilters). CRCs are so called because the ''check'' (data verification) value is a ''redundancy'' (it expands the message without adding information) and the algorithm is based on ''cyclic'' codes. CRCs are popular because they are simple to implement in binary hardware, easy to analyze mathematically, and particularly good at detecting common errors caused by noise in transmission channels. Because the check value has a fixed length, the function that generates it is occasionally used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Payload (computing)
In computing and telecommunications, the payload is the part of transmitted data that is the actual intended message. Headers and metadata are sent only to enable payload delivery. In the context of a computer virus or worm, the payload is the portion of the malware which performs malicious action. The term is borrowed from transportation, where '' payload'' refers to the part of the load that ''pays'' for transportation. Networking In computer networking, data to be transmitted is the payload. It is almost always encapsulated in some type of frame format, composed of framing bits and a frame check sequence. Examples are Ethernet frames, Point-to-Point Protocol (PPP) frames, Fibre Channel frames, and V.42 modem frames. Programming In computer programming, the most common usage of the term is in the context of message protocols, to differentiate the protocol overhead from the actual data. For example, a JSON web service response might be: The string ''Hello, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CRC-32
A cyclic redundancy check (CRC) is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to digital data. Blocks of data entering these systems get a short ''check value'' attached, based on the remainder of a polynomial division of their contents. On retrieval, the calculation is repeated and, in the event the check values do not match, corrective action can be taken against data corruption. CRCs can be used for error correction (see bitfilters). CRCs are so called because the ''check'' (data verification) value is a ''redundancy'' (it expands the message without adding information) and the algorithm is based on ''cyclic'' codes. CRCs are popular because they are simple to implement in binary hardware, easy to analyze mathematically, and particularly good at detecting common errors caused by noise in transmission channels. Because the check value has a fixed length, the function that generates it is occasionally used as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
