1.
Dressing (medical)
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A dressing is a sterile pad or compress applied to a wound to promote healing and protect the wound from further harm. A dressing is designed to be in contact with the wound, as distinguished from a bandage. A dressing can have a number of purposes, depending on the type, severity and position of the wound, although all purposes are focused towards promoting recovery and protecting from further harm. Ultimately, the aim of a dressing is to promote healing of the wound by providing a sterile, breathable and this will then reduce the risk of infection, help the wound heal more quickly, and reduce scarring. Historically, dressings were made of a piece of material, usually a cloth, however, modern dressings include dry or impregnated gauze, plastic films, gels, foams, hydrocolloids, alginates, hydrogels, and polysaccharide pastes, granules and beads. Pressure dressings are used to treat burns and after skin grafts. They apply pressure and prevent fluids from collecting in the tissue, dressings can also regulate the chemical environment of a wound, usually with the aim of preventing infection by the impregnation of topical antiseptic chemicals. Commonly used antiseptics include povidone-iodine, boracic lint dressings or historically castor oil, antibiotics are also often used with dressings to prevent bacterial infection. Medical grade honey is another option, and there is moderate evidence that honey dressings are more effective than common antiseptic. Bioelectric dressings can be effective in attacking certain antibiotic-resistant bacteria and speeding up the healing process, dressings are also often impregnated with analgesics to reduce pain. The physical features of a dressing can impact the efficacy of such topical medications, occlusive dressings, made from substances impervious to moisture such as plastic or latex, can be used to increase their rate of absorption into the skin. Dressings are usually secured with adhesive tape and/or a bandage, many dressings today are produced as an island surrounded by an adhesive backing, ready for immediate application – these are known as island dressings. Gauze dressings are the most commonly used dressing due to their simplicity and inexpensiveness, constructed from an open-weave fabric, usually cotton, traditional gauze dressings function as an absorbent, breathable and protective pad for a wound. Non-stick gauze island dressings are the most common type of dressing today – an example is the Band-Aid, advancements in understanding of wounds have commanded biomedical innovations in the treatment of acute, chronic, and other types of wounds. Many biologics, skin substitutes, biomembranes and scaffolds have been developed to facilitate wound healing through various mechanisms, applying a dressing is a first aid skill, although many people undertake the practice with no training – especially on minor wounds. Modern dressings will almost all come in a prepackaged sterile wrapping, sterility is necessary to prevent infection from pathogens resident within the dressing. Historically, and still the case in less developed areas and in an emergency. This can consist of anything, including clothing or spare material, applying and changing dressings is one common task in nursing
2.
Data compression
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In signal processing, data compression, source coding, or bit-rate reduction involves encoding information using fewer bits than the original representation. Compression can be lossy or lossless. Lossless compression reduces bits by identifying and eliminating statistical redundancy, no information is lost in lossless compression. Lossy compression reduces bits by removing unnecessary or less important information, the process of reducing the size of a data file is referred to as data compression. In the context of data transmission, it is called coding in opposition to channel coding. Compression is useful because it reduces resources required to store and transmit data, computational resources are consumed in the compression process and, usually, in the reversal of the process. Data compression is subject to a space–time complexity trade-off, Lossless data compression algorithms usually exploit statistical redundancy to represent data without losing any information, so that the process is reversible. Lossless compression is possible because most real-world data exhibits statistical redundancy, for example, an image may have areas of color that do not change over several pixels, instead of coding red pixel, red pixel. The data may be encoded as 279 red pixels and this is a basic example of run-length encoding, there are many schemes to reduce file size by eliminating redundancy. The Lempel–Ziv compression methods are among the most popular algorithms for lossless storage, DEFLATE is a variation on LZ optimized for decompression speed and compression ratio, but compression can be slow. DEFLATE is used in PKZIP, Gzip, and PNG, LZW is used in GIF images. LZ methods use a table-based compression model where table entries are substituted for repeated strings of data, for most LZ methods, this table is generated dynamically from earlier data in the input. The table itself is often Huffman encoded, current LZ-based coding schemes that perform well are Brotli and LZX. LZX is used in Microsofts CAB format, the best modern lossless compressors use probabilistic models, such as prediction by partial matching. The Burrows–Wheeler transform can also be viewed as a form of statistical modelling. The basic task of grammar-based codes is constructing a context-free grammar deriving a single string, sequitur and Re-Pair are practical grammar compression algorithms for which software is publicly available. In a further refinement of the use of probabilistic modelling. Arithmetic coding is a more modern coding technique that uses the mathematical calculations of a machine to produce a string of encoded bits from a series of input data symbols
3.
Unix shell
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A Unix shell is a command-line interpreter or shell that provides a traditional Unix-like command line user interface. Users direct the operation of the computer by entering commands as text for a command line interpreter to execute, users typically interact with a Unix shell using a terminal emulator, however, direct operation via serial hardware connections, or networking session, are common for server systems. All Unix shells provide filename wildcarding, piping, here documents, command substitution, variables and control structures for condition-testing, the most generic sense of the term shell means any program that users employ to type commands. In Unix-like operating systems, users typically have many choices of command-line interpreters for interactive sessions, when a user logs in to the system interactively, a shell program is automatically executed for the duration of the session. The Unix shell is both a command language as well as a scripting programming language, and is used by the operating system as the facility to control the execution of the system. Shells created for operating systems often provide similar functionality. On hosts with a system, like macOS, some users may never use the shell directly. However, some vendors have replaced the traditional shell-based startup system with different approaches. The first Unix shell was the Thompson shell, sh, written by Ken Thompson at Bell Labs and distributed with Versions 1 through 6 of Unix, though not in current use, it is still available as part of some Ancient UNIX Systems. It was modeled after the Multics shell, itself modeled after the RUNCOM program Louis Pouzin showed to the Multics Team, the rc suffix on some Unix configuration files, is a remnant of the RUNCOM ancestry of Unix shells. The PWB shell or Mashey shell, sh, was a version of the Thompson shell, augmented by John Mashey and others and distributed with the Programmers Workbench UNIX. It focused on making shell programming practical, especially in large shared computing centers and it added shell variables, user-executable shell scripts, and interrupt-handling. Control structures were extended from if/goto to if/then/else/endif, switch/breaksw/endsw, as shell programming became widespread, these external commands were incorporated into the shell itself for performance. But the most widely distributed and influential of the early Unix shells were the Bourne shell, both shells have been used as the coding base and model for many derivative and work-alike shells with extended feature sets. The Bourne shell, sh, was a rewrite by Stephen Bourne at Bell Labs. The language, including the use of a keyword to mark the end of a block, was influenced by ALGOL68. Traditionally, the Bourne shell program name is sh and its path in the Unix file system hierarchy is /bin/sh, but a number of compatible work-alikes are also available with various improvements and additional features. The sh of FreeBSD, NetBSD are based on ash that has enhanced to be POSIX conformant for the occasion
4.
Gzip
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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 replacement for the compress program used in early Unix systems. Version 0.1 was first publicly released on 31 October 1992, 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, although its file format also allows for multiple such streams to be concatenated, gzip is normally used to compress just single files. Compressed archives are created by assembling collections of files into a single tar archive. The final. tar. gz or. tgz file is called a tarball. Gzip is not to be confused with the ZIP archive format, various implementations of the program have been written. The most commonly known is the GNU Projects implementation using Lempel-Ziv coding, openBSDs version of gzip is actually the compress program, to which support for the gzip format was added in OpenBSD3.4. The g in this specific version stands for gratis and these implementations originally come from NetBSD, and supports decompression of bzip2 and the Unix pack format. The tar utility included in most Linux distributions can extract. tar. gz files by passing the z option, zlib is an abstraction of the DEFLATE algorithm in library form which includes support both for the gzip file format and a lightweight stream format in its API. The zlib stream format, DEFLATE, and the file format were standardized respectively as RFC1950, RFC1951. The gzip format is used in HTTP compression, a used to speed up the sending of HTML. It is one of the three formats for HTTP compression as specified in RFC2616. This RFC also specifies a zlib format, which is equal to the gzip format except that gzip adds eleven bytes of overhead in the form of headers and trailers. Still, the format is sometimes recommended over zlib because Microsoft Internet Explorer does not implement the standard correctly. Zlib DEFLATE is used internally by the Portable Network Graphics format, since the late 1990s, bzip2, a file compression utility based on a block-sorting algorithm, has gained some popularity as a gzip replacement. It produces considerably smaller files, but at the cost of memory, comparison of file archivers Free file format List of archive formats List of Unix programs GNU Gzip home page Original gzip Home Page
5.
Bzip2
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Bzip2 is a free and open-source file compression program that uses the Burrows–Wheeler algorithm. It only compresses single files and is not a file archiver and it is developed and maintained by Julian Seward. Seward made the first public release of bzip2, version 0.15, the compressors stability and popularity grew over the next several years, and Seward released version 1.0 in late 2000. Bzip2 compresses most files more effectively than the older LZW and Deflate compression algorithms, LZMA is generally more space-efficient than bzip2 at the expense of even slower compression speed, while having much faster decompression. Bzip2 compresses data in blocks of size between 100 and 900 kB and uses the Burrows–Wheeler transform to convert frequently-recurring character sequences into strings of identical letters and it then applies move-to-front transform and Huffman coding. Bzip2s ancestor bzip used arithmetic coding instead of Huffman, the change was made because of a software patent restriction. Bzip2 performance is asymmetric, as decompression is relatively fast, as of May 2010, this functionality has not been incorporated into the main project. Like gzip, bzip2 is only a data compressor, thus the sequence AAAAAAABBBBCCCD is replaced with AAAA\3BBBB\0CCCD, where \3 and \0 represent byte values 3 and 0 respectively. Runs of symbols are always transformed after four consecutive symbols, even if the run-length is set to zero, in the worst case, it can cause an expansion of 1.25 and best case a reduction to <0.02. While the specification allows for runs of length 256–259 to be encoded. The author of bzip2 has stated that the RLE step was a mistake and was only intended to protect the original BWT implementation from pathological cases. This is the reversible block-sort that is at the core of bzip2, the block is entirely self-contained, with input and output buffers remaining the same size—in bzip2, the operating limit for this stage is 900 kB. For the block-sort, a matrix is created in which row i contains the whole of the buffer, following rotation, the rows of the matrix are sorted into alphabetic order. A 24-bit pointer is stored marking the position for when the block is untransformed. In practice, it is not necessary to construct the matrix, rather. The output buffer is the last column of the matrix, this contains the whole buffer, again, this transform does not alter the size of the processed block. Each of the symbols in use in the document is placed in an array, when a symbol is processed, it is replaced by its location in the array and that symbol is shuffled to the front of the array. The effect is that immediately recurring symbols are replaced by zero symbols, much natural data contains identical symbols that recur within a limited range
