1.
Evince
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Evince is a document viewer for PDF, PostScript, DjVu, TIFF, XPS and DVI formats. It was designed for the GNOME desktop environment, the developers of Evince intended to replace the multiple GNOME document viewers with a single and simple application. The Evince motto sums up the project aim, Simply a Document Viewer, GNOME releases have included Evince since GNOME2.12. Evince code consists mainly of C, with a part written in C++. A large number of Linux distributions – including Ubuntu, Fedora, Evince is free and open-source software subject to the requirements of the GNU General Public License version 2 or later. The Evince FAQ highlights the meaning of the word Evince as to show or express something clearly, Evince began as a rewrite of GPdf, which its support programmers had started to find unwieldy to maintain. Evince quickly surpassed the functionality of GPdf and replaced both GPdf and GGV in the September 2005 release of GNOME2.12, Evince is included on the VALO-CD, a collection of all the best Windows programs. Evince incorporates a search that displays the number of results found. Users can optionally display thumbnails of pages to assist in page navigation within a document, when documents support indices, Evince gives the option of showing the document index for quickly moving from one section to another. Evince can show two pages at a time, left and right, and offers full-screen and slide-show views, Evince allows the selection of text in PDF files and allows users to highlight and copy text from documents made from scanned images, if the PDF includes OCR data. Evince used to obey the DRM restrictions of PDF files, which may prevent copying, printing, or converting some PDF files, however this has been made optional, and turned off by default in gconf. Evince supports many different single and multi-page document formats, Built-in support PDF using the Poppler backend PostScript using the Ghostscript backend, the Windows package of Evince ships with a copy of Ghostscripts libgs version 8, so no external Ghostscript installation is needed on that platform
2.
TeX
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TeX is a typesetting system designed and mostly written by Donald Knuth and released in 1978. TeX is free software, which has made it accessible to a wider range of users. TeX is a means by which to typeset complex mathematical formulae. TeX is popular in academia, especially in mathematics, computer science, economics, engineering, physics, statistics and it has largely displaced Unix troff, the other favored formatting system, in many Unix installations, which use both for different purposes. It is also used for many other typesetting tasks, especially in the form of LaTeX, ConTeXt, the widely used MIME type for TeX is application/x-tex. Within the typesetting system, its name is stylized as TeX, when the first paper volume of Donald Knuths The Art of Computer Programming was published in 1968, it was typeset using hot metal typesetting set by a Monotype Corporation typecaster. This method, dating back to the 19th century, produced a classic style appreciated by Knuth. When Knuth received the proofs of the new book on 30 March 1977. Around that time, Knuth saw for the first time the output of a high-quality digital typesetting system, the disappointing galley proofs gave him the final motivation to solve the problem at hand once and for all by designing his own typesetting system. On 13 May 1977, he wrote a memo to himself describing the features of TeX. He planned to finish it on his sabbatical in 1978, but as it happened the language was not frozen until 1989, guy Steele happened to be at Stanford during the summer of 1978, when Knuth was developing his first version of TeX. When Steele returned to Massachusetts Institute of Technology that autumn, he rewrote TeXs input/output to run under the Incompatible Timesharing System operating system, the first version of TeX was written in the SAIL programming language to run on a PDP-10 under Stanfords WAITS operating system. For later versions of TeX, Knuth invented the concept of literate programming, the language used is called WEB and produces programs in DEC PDP-10 Pascal. A new version of TeX, rewritten from scratch and called TeX82, was published in 1982, among other changes, the original hyphenation algorithm was replaced by a new algorithm written by Frank Liang. In 1989, Donald Knuth released new versions of TeX and METAFONT and this is a reflection of the fact that TeX is now very stable, and only minor updates are anticipated. The current version of TeX is 3.14159265, it was last updated 2014-01-12, the design was frozen after version 3.0, and no new feature or fundamental change will be added, so all newer versions will contain only bug fixes. For this reason, he has stated that the final change will be to change the version number to π. Likewise, versions of METAFONT after 2.0 asymptotically approach e, for example, the Omega project was developed after 1991, primarily to enhance TeXs multilingual typesetting abilities
3.
Typesetting
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Typesetting is the composition of text by means of arranging physical types or the digital equivalents. Stored letters and other symbols are retrieved and ordered according to a languages orthography for visual display, typesetting requires the prior process of designing a font. One significant effect of typesetting was that authorship of works could be spotted more easily, during much of the letterpress era, movable type was composed by hand for each page. The form was placed in a press, inked, and an impression made on paper. During typesetting, individual sorts are picked from a case with the right hand, and set into a composing stick held in the left hand from left to right. This is reputed to be the origin of the expression mind your ps and it might just as easily have been “mind your bs and ds”. The diagram at right illustrates a cast metal sort, a face, b body or shank, wooden printing sorts were in use for centuries in combination with metal type. Not shown, and more the concern of the casterman, is the “set”, set width, like body size, is measured in points. This was particularly prevalent in book and newspaper work where rotary presses required type forms to wrap an impression cylinder rather than set in the bed of a press, advances such as the typewriter and computer would push the state of the art even farther ahead. Still, hand composition and letterpress printing have not fallen out of use. However, it is a small niche within the larger typesetting market. The time and effort required to compose the text led to several efforts in the 19th century to produce mechanical typesetting. Most of the systems involved the in-house casting of the type to be used. The Linotype machine, invented in 1884, used a keyboard to assemble the casting matrices, in the Monotype System, a keyboard was used to punch a paper tape, which was then fed to control a casting machine. The Ludlow Typograph involved hand-set matrices, but otherwise used hot metal, by the early 20th century, the various systems were nearly universal in large newspapers and publishing houses. Phototypesetting or cold type systems first appeared in the early 1960s and these devices consisted of glass disks that spun in front of a light source to selectively expose characters onto light-sensitive paper. Originally they were driven by pre-punched paper tapes, later they were hooked up to computer front ends. One of the earliest electronic photocomposition systems was introduced by Fairchild Semiconductor, the typesetter typed a line of text on a Fairchild keyboard that had no display
4.
Donald Knuth
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Donald Ervin Knuth is an American computer scientist, mathematician, and professor emeritus at Stanford University. He is the author of the multi-volume work The Art of Computer Programming and he contributed to the development of the rigorous analysis of the computational complexity of algorithms and systematized formal mathematical techniques for it. In the process he also popularized the asymptotic notation, Knuth strongly opposes granting software patents, having expressed his opinion to the United States Patent and Trademark Office and European Patent Organization. Knuth was born in Milwaukee, Wisconsin, to German-Americans Ervin Henry Knuth and his father had two jobs, running a small printing company and teaching bookkeeping at Milwaukee Lutheran High School. Donald, a student at Milwaukee Lutheran High School, received academic accolades there, for example, in eighth grade, he entered a contest to find the number of words that the letters in Zieglers Giant Bar could be rearranged to create. Although the judges only had 2,500 words on their list, Donald found 4,500 words, as prizes, the school received a new television and enough candy bars for all of his schoolmates to eat. Knuth had a time choosing physics over music as his major at Case Institute of Technology. He also joined Beta Nu Chapter of the Theta Chi fraternity, while studying physics at the Case Institute of Technology, Knuth was introduced to the IBM650, one of the early mainframes. After reading the manual, Knuth decided to rewrite the assembly and compiler code for the machine used in his school. In 1958, Knuth created a program to help his schools basketball team win their games and he assigned values to players in order to gauge their probability of getting points, a novel approach that Newsweek and CBS Evening News later reported on. Knuth was one of the editors of the Engineering and Science Review. In 1963, with mathematician Marshall Hall as his adviser, he earned a PhD in mathematics from the California Institute of Technology, after receiving his PhD, Knuth joined Caltechs faculty as an associate professor. He accepted a commission to write a book on computer programming language compilers and he originally planned to publish this as a single book. As Knuth developed his outline for the book, he concluded that he required six volumes and he published the first volume in 1968. Knuth then left this position to join the Stanford University faculty, Knuth is a writer as well as a computer scientist. Knuth has been called the father of the analysis of algorithms, in the 1970s, Knuth described computer science as a totally new field with no real identity. And the standard of available publications was not that high, a lot of the papers coming out were quite simply wrong. So one of my motivations was to put straight a story that had been very badly told, by 2013, the first three volumes and part one of volume four of his series had been published
5.
Human-readable medium
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A human-readable medium or human-readable format is a representation of data or information that can be naturally read by humans. In computing, human-readable data is encoded as ASCII or Unicode text. In many jurisdictions, barcode labels used in retail shopping must also include a price on the merchandise. In addition, these representations can be compressed very effectively for transmission or storage. Human readable protocols greatly reduce the cost of debugging, various organizations have standardized the definition of human-readable and machine-readable data and how they are applied in their respective fields of application, e. g. the Universal Postal Union. Occasionally human-readable is used to describe ways of encoding an arbitrary integer into a series of English words. Compared to decimal or other compact binary-to-text encoding systems, English words are easier for humans to read, remember, and type in
6.
Binary file
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A binary file is a computer file that is not a text file. The term binary file is used as a term meaning non-text file. Binary files are usually thought of as being a sequence of bytes, binary files typically contain bytes that are intended to be interpreted as something other than text characters. Compiled computer programs are examples, indeed, compiled applications are sometimes referred to, particularly by programmers. But binary files can also mean that they contain images, sounds, compressed versions of files, etc. — in short. Some binary files contain headers, blocks of metadata used by a program to interpret the data in the file. The header often contains a signature or magic number which can identify the format, for example, a GIF file can contain multiple images, and headers are used to identify and describe each block of image data. The leading bytes of the header would contain text like GIF87a or GIF89a that can identify the binary as a GIF file, if a binary file does not contain any headers, it may be called a flat binary file. To send binary files through certain systems that do not allow all data values, encoding the data has the disadvantage of increasing the file size during the transfer, as well as requiring translation back into binary after receipt. See Binary-to-text encoding for more on this subject, a hex editor or viewer may be used to view file data as a sequence of hexadecimal values for corresponding bytes of a binary file. If a binary file is opened in an editor, each group of eight bits will typically be translated as a single character. Other type of viewers simply replace the characters with spaces revealing only the human-readable text. This type of view is useful for inspection of a binary file in order to find passwords in games, find hidden text in non-text files. It can even be used to inspect suspicious files for unwanted effects, for example, the user would see any URL/email to which the suspected software may attempt to connect in order to upload unapproved data. If the file is itself treated as an executable and run, standards are very important to binary files. For example, a binary file interpreted by the ASCII character set will result in text being displayed, a custom application can interpret the file differently, a byte may be a sound, or a pixel, or even an entire word. Binary itself is meaningless, until such time as an executed algorithm defines what should be done with each bit, byte, thus, just examining the binary and attempting to match it against known formats can lead to the wrong conclusion as to what it actually represents. This fact can be used in steganography, where an algorithm interprets a binary data file differently to reveal hidden content, without the algorithm, it is impossible to tell that hidden content exists
7.
Computer monitor
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A computer monitor or a computer display is an electronic visual display for computers. A monitor usually comprises the display device, circuitry, casing, the display device in modern monitors is typically a thin film transistor liquid crystal display or a flat panel LED display, while older monitors used a cathode ray tubes. It can be connected to the computer via VGA, DVI, HDMI, DisplayPort, Thunderbolt, LVDS or other proprietary connectors, originally, computer monitors were used for data processing while television receivers were used for entertainment. From the 1980s onwards, computers have used for both data processing and entertainment, while televisions have implemented some computer functionality. The common aspect ratio of televisions, and computer monitors, has changed from 4,3 to 16,10, to 16,9. Early electronic computers were fitted with a panel of light bulbs where the state of each particular bulb would indicate the state of a particular register bit inside the computer. This allowed the operating the computer to monitor the internal state of the machine. As early monitors were only capable of displaying a limited amount of information. Instead, a printer was the primary output device, while the monitor was limited to keeping track of the programs operation. Multiple technologies have used for computer monitors. Until the 21st century most used cathode ray tubes but they have largely superseded by LCD monitors. The first computer monitors used cathode ray tubes, high-resolution CRT displays were developed for specialized military, industrial and scientific applications but they were far too costly for general use. Either computer could be connected to the terminals of an ordinary color TV set or used with a purpose-made CRT color monitor for optimum resolution. In 1984 IBM introduced the Enhanced Graphics Adapter which was capable of producing 16 colors and had a resolution of 640 x 350, by the end of the 1980s color CRT monitors that could clearly display 1024 x 768 pixels were widely available and increasingly affordable. During the following decade maximum display resolutions gradually increased and prices continued to fall, CRT technology remained dominant in the PC monitor market into the new millennium partly because it was cheaper to produce and offered viewing angles close to 180 degrees. CRTs still offer some image quality advantages over LCDs but improvements to the latter have made much less obvious. There are multiple technologies that have used to implement liquid crystal displays. Commonly, the laptop would be offered with an assortment of display options at increasing price points, monochrome
8.
Printer (computing)
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In computing, a printer is a peripheral which makes a persistent human-readable representation of graphics or text on paper or similar physical media. The worlds first computer printer was a 19th-century mechanically driven apparatus invented by Charles Babbage for his difference engine, the plotter was used for those requiring high quality line art like blueprints. Laser printers using PostScript mixed text and graphics, like dot-matrix printers, by 1990, most simple printing tasks like fliers and brochures were now created on personal computers and then laser printed, expensive offset printing systems were being dumped as scrap. The HP Deskjet of 1988 offered the same advantages as laser printer in terms of flexibility, inkjet systems rapidly displaced dot matrix and daisy wheel printers from the market. By the 2000s high-quality printers of this sort had fallen under the price point. Even the desire for printed output for offline reading while on mass transit or aircraft has been displaced by e-book readers, today, traditional printers are being used more for special purposes, like printing photographs or artwork, and are no longer a must-have peripheral. Starting around 2010, 3D printing became an area of intense interest and these devices are in their earliest stages of development and have not yet become commonplace. Personal printers are designed to support individual users, and may be connected to only a single computer. These printers are designed for low-volume, short-turnaround print jobs, requiring minimal setup time to produce a copy of a given document. However, they are generally slow devices ranging from 6 to around 25 pages per minute, however, this is offset by the on-demand convenience. Some printers can print documents stored on cards or from digital cameras. Networked or shared printers are designed for high-volume, high-speed printing and they are usually shared by many users on a network and can print at speeds of 45 to around 100 ppm. The Xerox 9700 could achieve 120 ppm, a virtual printer is a piece of computer software whose user interface and API resembles that of a printer driver, but which is not connected with a physical computer printer. It is called a printer by analogy with a printer which produces a two-dimensional document by a similar process of depositing a layer of ink on paper. The choice of print technology has an effect on the cost of the printer and cost of operation, speed, quality and permanence of documents. Some printer technologies dont work with certain types of physical media, cheques can be printed with liquid ink or on special cheque paper with toner anchorage so that alterations may be detected. The machine-readable lower portion of a cheque must be printed using MICR toner or ink, banks and other clearing houses employ automation equipment that relies on the magnetic flux from these specially printed characters to function properly. The following printing technologies are found in modern printers, A laser printer rapidly produces high quality text
9.
PostScript
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PostScript is a page description language in the electronic publishing and desktop publishing business. It is a typed, concatenative programming language and was created at Adobe Systems by John Warnock, Charles Geschke, Doug Brotz, Ed Taft. The concepts of the PostScript language were seeded in 1976 when John Warnock was working at Evans & Sutherland, at that time John Warnock was developing an interpreter for a large three-dimensional graphics database of New York harbor. Warnock conceived the Design System language to process the graphics, concurrently, researchers at Xerox PARC had developed the first laser printer and had recognized the need for a standard means of defining page images. In 1975-76 Bob Sproull and William Newman developed the Press format, but Press, a data format rather than a language, lacked flexibility, and PARC mounted the Interpress effort to create a successor. In 1978 Evans & Sutherland asked Warnock to move from the San Francisco Bay Area to their headquarters in Utah. He then joined Xerox PARC to work with Martin Newell and they rewrote Design System to create J & M which was used for VLSI design and the investigation of type and graphics printing. This work later evolved and expanded into the Interpress language, Warnock left with Chuck Geschke and founded Adobe Systems in December 1982. They, together with Doug Brotz, Ed Taft and Bill Paxton created a language, similar to Interpress, called PostScript. At about this time they were visited by Steve Jobs, who urged them to adapt PostScript to be used as the language for driving laser printers. In March 1985, the Apple LaserWriter was the first printer to ship with PostScript, the combination of technical merits and widespread availability made PostScript a language of choice for graphical output for printing applications. For a time an interpreter for the PostScript language was a component of laser printers. However, the cost of implementation was high, computers output raw PS code that would be interpreted by the printer into an image at the printers natural resolution. This required high performance microprocessors and ample memory, the LaserWriter used a 12 MHz Motorola 68000, making it faster than any of the Macintosh computers to which it attached. When the laser printer engines themselves cost over a thousand dollars the added cost of PS was marginal, the first version of the PostScript language was released to the market in 1984. The term Level 1 was added when Level 2 was introduced, PostScript 3 came at the end of 1997, and along with many new dictionary-based versions of older operators, introduced better color handling, and new filters. Prior to the introduction of PostScript, printers were designed to print character output given the text—typically in ASCII—as input and this changed to some degree with the increasing popularity of dot matrix printers. The characters on these systems were drawn as a series of dots, dot matrix printers also introduced the ability to print raster graphics
10.
Portable Document Format
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The Portable Document Format is a file format used to present documents in a manner independent of application software, hardware, and operating systems. Each PDF file encapsulates a complete description of a fixed-layout flat document, including the text, fonts, graphics, PDF was developed in the early 1990s as a way to share computer documents, including text formatting and inline images. It was among a number of competing formats such as DjVu, Envoy, Common Ground Digital Paper, Farallon Replica, in those early years before the rise of the World Wide Web and HTML documents, PDF was popular mainly in desktop publishing workflows. Adobe Systems made the PDF specification available free of charge in 1993 and these proprietary technologies are not standardized and their specification is published only on Adobe’s website. Many of them are not supported by popular third-party implementations of PDF. So when organizations publish PDFs which use proprietary technologies, they present accessibility issues for some users. In 2014, ISO TC171 voted to deprecate XFA for ISO 32000-2, on January 9,2017, the final draft for ISO 32000-2 was published, thus reaching the approval stage. The PDF combines three technologies, A subset of the PostScript page description programming language, for generating the layout, a font-embedding/replacement system to allow fonts to travel with the documents. A structured storage system to bundle these elements and any associated content into a single file, PostScript is a page description language run in an interpreter to generate an image, a process requiring many resources. It can handle graphics and standard features of programming such as if. PDF is largely based on PostScript but simplified to remove flow control features like these, often, the PostScript-like PDF code is generated from a source PostScript file. The graphics commands that are output by the PostScript code are collected and tokenized, any files, graphics, or fonts to which the document refers also are collected. Then, everything is compressed to a single file, therefore, the entire PostScript world remains intact. PDF supports graphic transparency, PostScript does not, PostScript is an interpreted programming language with an implicit global state, so instructions accompanying the description of one page can affect the appearance of any following page. Therefore, all preceding pages in a PostScript document must be processed to determine the appearance of a given page. A PDF file is a 7-bit ASCII file, except for elements that may have binary content. A PDF file starts with a header containing the magic number, the format is a subset of a COS format. A COS tree file consists primarily of objects, of which there are eight types, Boolean values, representing true or false Numbers Strings, enclosed within parentheses, objects may be either direct or indirect
11.
Encryption
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In cryptography, encryption is the process of encoding a message or information in such a way that only authorized parties can access it. Encryption does not of itself prevent interference, but denies the intelligible content to a would-be interceptor, in an encryption scheme, the intended information or message, referred to as plaintext, is encrypted using an encryption algorithm, generating ciphertext that can only be read if decrypted. For technical reasons, an encryption scheme usually uses an encryption key generated by an algorithm. It is in possible to decrypt the message without possessing the key. An authorized recipient can decrypt the message with the key provided by the originator to recipients. In symmetric-key schemes, the encryption and decryption keys are the same, communicating parties must have the same key before they can achieve secure communication. In public-key encryption schemes, the key is published for anyone to use. However, only the party has access to the decryption key that enables messages to be read. Public-key encryption was first described in a document in 1973. Encryption has long used by militaries and governments to facilitate secret communication. It is now used in protecting information within many kinds of civilian systems. Encryption can be used to protect data at rest, such as stored on computers. In recent years, there have been reports of confidential data, such as customers personal records. Encrypting such files at rest helps protect them should physical security measures fail, in response to encryption of data at rest, cyber-adversaries have developed new types of attacks. There have been reports of data in transit being intercepted in recent years. Data should also be encrypted when transmitted across networks in order to protect against eavesdropping of network traffic by unauthorized users, standards for cryptographic software and hardware to perform encryption are widely available, but successfully using encryption to ensure security may be a challenging problem. A single error in design or execution can allow successful attacks. Sometimes an adversary can obtain unencrypted information without directly undoing the encryption, see, e. g. traffic analysis, TEMPEST, or Trojan horse
12.
LaTeX
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LaTeX is a document preparation system. When writing, the writer uses plain text as opposed to the text found in WYSIWYG word processors like Microsoft Word or LibreOffice Writer. The writer uses markup tagging conventions to define the structure of a document, to stylise text throughout a document. A TeX distribution such as TeX Live or MikTeX is used to produce a file suitable for printing or digital distribution. Within the typesetting system, its name is stylised as LaTeX and it also has a prominent role in the preparation and publication of books and articles that contain complex multilingual materials, such as Tamil, Sanskrit and Greek. LaTeX uses the TeX typesetting program for formatting its output, LaTeX can be used as a standalone document preparation system or as an intermediate format. In the latter role, for example, it is used as part of a pipeline for translating DocBook. LaTeX is intended to provide a language that accesses the power of TeX in an easier way for writers. In short, TeX handles the layout side, while LaTeX handles the content side for document processing, LaTeX comprises a collection of TeX macros and a program to process LaTeX documents. LaTeX was originally written in the early 1980s by Leslie Lamport at SRI International, LaTeX is free software and is distributed under the LaTeX Project Public License. It therefore encourages the separation of layout from content while still allowing manual typesetting adjustments where needed and this concept is similar to the mechanism by which many word processors allow styles to be defined globally for an entire document or the use of Cascading Style Sheets to style HTML. The LaTeX system is a language that also handles typesetting and rendering. LaTeX can be extended by using the underlying macro language to develop custom formats. Such macros are often collected into packages, which are available to address special formatting such as complicated mathematical content or graphics. Indeed, in the example below, the environment is provided by the amsmath package. In order to create a document in LaTeX, you first write a file, say document. tex, then you give your document. tex file as input to the TeX program, and TeX writes out a file suitable for viewing onscreen or printing. This write-format-preview cycle is one of the ways in which working with LaTeX differs from what-you-see-is-what-you-get word-processing. It is similar to the code-compile-execute cycle familiar to computer programmers, today, many LaTeX-aware editing programs make this cycle a simple matter of pressing a single key, while showing the output preview on the screen beside the input window
13.
Machine code
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Machine code or machine language is a set of instructions executed directly by a computers central processing unit. Each instruction performs a specific task, such as a load. Every program directly executed by a CPU is made up of a series of such instructions, numerical machine code may be regarded as the lowest-level representation of a compiled or assembled computer program or as a primitive and hardware-dependent programming language. While it is possible to write directly in numerical machine code, it is tedious and error prone to manage individual bits and calculate numerical addresses. For this reason machine code is almost never used to programs in modern contexts. Almost all practical programs today are written in languages or assembly language. However, the interpreter itself, which may be seen as an executor or processor, performing the instructions of the source code, every processor or processor family has its own machine code instruction set. Instructions are patterns of bits that by physical design correspond to different commands to the machine, thus, the instruction set is specific to a class of processors using the same architecture. Successor or derivative processor designs often include all the instructions of a predecessor, systems may also differ in other details, such as memory arrangement, operating systems, or peripheral devices. Because a program normally relies on such factors, different systems will not run the same machine code. A machine code instruction set may have all instructions of the same length, how the patterns are organized varies strongly with the particular architecture and often also with the type of instruction. Not all machines or individual instructions have explicit operands, an accumulator machine has a combined left operand and result in an implicit accumulator for most arithmetic instructions. Other architectures have accumulator versions of common instructions, with the accumulator regarded as one of the general registers by longer instructions, a stack machine has most or all of its operands on an implicit stack. Special purpose instructions also often lack explicit operands and this distinction between explicit and implicit operands is important in machine code generators, especially in the register allocation and live range tracking parts. A good code optimizer can track implicit as well as explicit operands which may allow more frequent constant propagation, constant folding of registers, a computer program is a sequence of instructions that are executed by a CPU. While simple processors execute instructions one after another, superscalar processors are capable of executing several instructions at once, program flow may be influenced by special jump instructions that transfer execution to an instruction other than the numerically following one. Conditional jumps are taken or not depending on some condition, a much more readable rendition of machine language, called assembly language, uses mnemonic codes to refer to machine code instructions, rather than using the instructions numeric values directly. For example, on the Zilog Z80 processor, the machine code 00000101, the MIPS instruction set provides a specific example for a machine code whose instructions are always 32 bits long
14.
Stack (abstract data type)
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The order in which elements come off a stack gives rise to its alternative name, LIFO. Additionally, an operation may give access to the top without modifying the stack. Considered as a data structure, or more abstractly a sequential collection. This makes it possible to implement a stack as a linked list. A stack may be implemented to have a bounded capacity, if the stack is full and does not contain enough space to accept an entity to be pushed, the stack is then considered to be in an overflow state. The pop operation removes an item from the top of the stack, Stacks entered the computer science literature in 1946, in the computer design of Alan M. Turing as a means of calling and returning from subroutines. Subroutines had already implemented in Konrad Zuses Z4 in 1945. Klaus Samelson and Friedrich L. Bauer of Technical University Munich proposed the idea in 1955, the same concept was developed, independently, by the Australian Charles Leonard Hamblin in the first half of 1957. Stacks are often described by analogy to a stack of plates in a cafeteria. Clean plates are placed on top of the stack, pushing down any already there, when a plate is removed from the stack, the one below it pops up to become the new top. In many implementations, a stack has more operations than push, an example is top of stack, or peek, which observes the top-most element without removing it from the stack. Since this can be done with a pop and a push with the same data, an underflow condition can occur in the stack top operation if the stack is empty, the same as pop. Also, implementations often have a function which just returns whether the stack is empty, a stack can be easily implemented either through an array or a linked list. The following will demonstrate both implementations, using pseudocode, an array can be used to implement a stack, as follows. The first element is the bottom, resulting in array being the first element pushed onto the stack, some languages, notably those in the Forth family, are designed around language-defined stacks that are directly visible to and manipulated by the programmer. Javas library contains a Stack class that is a specialization of Vector, following is an example program in Java language, using that class. A common use of stacks at the level is as a means of allocating and accessing memory. A typical stack is an area of memory with a fixed origin
15.
TeX font metric
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TeX font metric is a font file format used by the TeX typesetting system. It is a font metric format, not an outline font format like TrueType, because it only the information necessary to typeset the font such as each characters width, height. The actual glyphs are stored elsewhere and this is not unique to TeX, Adobes AFM files and Windows PFM files use the same technique. TFM files contain all of the information TeX needs to produce its device-independent output, the actual glyphs are then inserted by the eventual DVI output driver or previewer, using, for instance, TrueType fonts, or fonts in METAFONTs PK format. The format is designed to be compact, in the original Computer Modern distribution. The canonical specification of the TFM format is embedded in the code of the program TFtoPL. A TFM file is broken down into a series of four-byte words, any data fields that are more than one byte long are held in big endian order. The six-word file header contains twelve unsigned 16-bit integers which describe the length of the file, the range of character codes contained in the font, a single TFM file describes between 0 and 256 characters, inclusive. The body of the TFM file consists of a series of ten tables, a 32-bit signed fixed-point number with 12 bits to the left of the decimal point, referred to as a fix_word, is used heavily. It also contains the design size, all following fix_word values are interpreted as multiplication factors for this. The next table, char_info, consists of one word per character and this is a device to save space, because width values, for instance, are frequently duplicated. Because height and depth values are duplicated more frequently, to fit all of these values into a single word, because of this, there is a limit of sixteen different character heights and sixteen different character depths in any given TFM file. Also, there is a limit of sixty-four different italic corrections, there is also one more index which can point into the lig_kern table, or to information about extensible characters, depending on a two-bit tag value. Extensible characters use a series of repeated characters to construct a large one of arbitrary size. There then follow the four tables width, height, depth and italic, extensible characters are specified in the exten table, using a series of four-byte words specifying the top, middle, bottom and repeated sections of an extensible character. For instance, the character at left below would be obtained by setting to the codes for. The first three character codes can be set to zero, for instance, if mid were set to 0 in the previous example, the result would change from the brace drawn at left to the parenthesis drawn to its right. / / | | | | < | | | | | \ \ Of course, the font would use specially designed characters for this, instead of reusing existing ones, but the principle is the same
16.
ASCII
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ASCII, abbreviated from American Standard Code for Information Interchange, is a character encoding standard. ASCII codes represent text in computers, telecommunications equipment, and other devices, most modern character-encoding schemes are based on ASCII, although they support many additional characters. ASCII was developed from telegraph code and its first commercial use was as a seven-bit teleprinter code promoted by Bell data services. Work on the ASCII standard began on October 6,1960, the first edition of the standard was published in 1963, underwent a major revision during 1967, and experienced its most recent update during 1986. Compared to earlier telegraph codes, the proposed Bell code and ASCII were both ordered for more convenient sorting of lists, and added features for other than teleprinters. Originally based on the English alphabet, ASCII encodes 128 specified characters into seven-bit integers as shown by the ASCII chart above. The characters encoded are numbers 0 to 9, lowercase letters a to z, uppercase letters A to Z, basic punctuation symbols, control codes that originated with Teletype machines, for example, lowercase j would become binary 1101010 and decimal 106. ASCII includes definitions for 128 characters,33 are non-printing control characters that affect how text and space are processed and 95 printable characters, of these, the IANA encourages use of the name US-ASCII for Internet uses of ASCII. The ASA became the United States of America Standards Institute and ultimately the American National Standards Institute, there was some debate at the time whether there should be more control characters rather than the lowercase alphabet. The X3.2.4 task group voted its approval for the change to ASCII at its May 1963 meeting, the X3 committee made other changes, including other new characters, renaming some control characters and moving or removing others. ASCII was subsequently updated as USAS X3. 4-1967, then USAS X3. 4-1968, ANSI X3. 4-1977 and they proposed a 9-track standard for magnetic tape, and attempted to deal with some punched card formats. The X3.2 subcommittee designed ASCII based on the earlier teleprinter encoding systems, like other character encodings, ASCII specifies a correspondence between digital bit patterns and character symbols. This allows digital devices to communicate each other and to process, store. Before ASCII was developed, the encodings in use included 26 alphabetic characters,10 numerical digits, ITA2 were in turn based on the 5-bit telegraph code Émile Baudot invented in 1870 and patented in 1874. The committee debated the possibility of a function, which would allow more than 64 codes to be represented by a six-bit code. In a shifted code, some character codes determine choices between options for the character codes. It allows compact encoding, but is reliable for data transmission. The standards committee decided against shifting, and so ASCII required at least a seven-bit code, the committee considered an eight-bit code, since eight bits would allow two four-bit patterns to efficiently encode two digits with binary-coded decimal
17.
Graphics
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Graphics are visual images or designs on some surface, such as a wall, canvas, screen, paper, or stone to inform, illustrate, or entertain. In contemporary usage it includes, pictorial representation of data, as in computer-aided design and manufacture, in typesetting and the graphic arts, images that are generated by a computer are called computer graphics. Examples are photographs, drawings, Line art, graphs, diagrams, typography, numbers, symbols, geometric designs, maps, engineering drawings, Graphics often combine text, illustration, and color. Graphic design may consist of the selection, creation, or arrangement of typography alone, as in a brochure, flyer, poster, web site. Clarity or effective communication may be the objective, association with cultural elements may be sought, or merely. Graphics can be functional or artistic. C, many of these were found to record astronomical, seasonal, and chronological details. Records from Egypt predate these and papyrus was used by the Egyptians as a material on which to plan the building of pyramids, they also used slabs of limestone, from 600–250 BC, the Greeks played a major role in geometry. They used graphics to represent their mathematical theories such as the Circle Theorem, in art, graphics is often used to distinguish work in a monotone and made up of lines, as opposed to painting. Drawing generally involves making marks on a surface by applying pressure from a tool, in which a tool is always used as if there were no tools it would be art. Graphical drawing is an instrumental guided drawing, woodblock printing, including images is first seen in China after paper was invented. In the West the main techniques have been woodcut, engraving and etching, etching is an intaglio method of printmaking in which the image is incised into the surface of a metal plate using an acid. The acid eats the metal, leaving behind roughened areas, or, if the surface exposed to the acid is very thin, the use of the process in printmaking is believed to have been invented by Daniel Hopfer of Augsburg, Germany, who decorated armour in this way. Etching is also used in the manufacturing of printed circuit boards, Line art is usually monochromatic, although lines may be of different colors. An illustration is a visual representation such as a drawing, painting, the aim of an illustration is to elucidate or decorate a story, poem or piece of textual information, traditionally by providing a visual representation of something described in the text. The editorial cartoon, also known as a cartoon, is an illustration containing a political or social message. Charts are often used to make it easier to understand large quantities of data, a diagram is a simplified and structured visual representation of concepts, ideas, constructions, relations, statistical data, etc. used to visualize and clarify the topic. A symbol, in its sense, is a representation of a concept or quantity, i. e. an idea, object, concept, quality. A map is a depiction of a space, a navigational aid which highlights relations between objects within that space
18.
Okular
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Okular is the document viewer for KDE SC4. It is based on KPDF and it replaced KPDF, KGhostView, KFax, KFaxview and its functionality can be easily embedded in other applications. Okular was started for the Google Summer of Code of 2005, Okular was identified as a success story of the 2007 Season of Usability. In this season the Okular toolbar mockup was created based on an analysis of other popular document viewers, okulars annotation features include commenting on PDF documents, highlighting and drawing lines, geometric shapes, adding textboxes, and stamps. Annotations are stored separately from the unmodified PDF file, or can be saved in the document as standard PDF annotations, text can be extracted to a text file. It is possible to select parts of the document and copy the text or image to the clipboard and this can be turned off in the options under Obey DRM limitations, however. List of PDF software Evince, the counterpart PDF viewer for GNOME Okular home page Okular user wiki
19.
Ghostscript
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Ghostscript is a suite of software based on an interpreter for Adobe Systems PostScript and Portable Document Format page description languages. Its main purposes are the rasterization or rendering of such page description language files, for the display or printing of document pages, and the conversion between PostScript and PDF files. Ghostscript can be used as an image processor for raster computer printers—for instance, as an input filter of line printer daemon—or as the RIP engine behind PostScript. Ghostscript can also be used as a file format converter, such as PostScript to PDF converter, the ps2pdf conversion program, which comes with the ghostscript distribution, is described by its documentation as a work-alike for nearly all the functionality of Adobes Acrobat Distiller product. This converter is basically a thin wrapper around ghostscripts pdfwrite output device, Ghostscript can also serve as the back-end for PDF to raster image converter, this is often combined with a PostScript printer driver in virtual printer PDF creators. As it takes the form of an interpreter, Ghostscript can also be used as a general purpose programming environment. Ghostscript has been ported to many operating systems, including Unix-like systems, classic Mac OS, OpenVMS, Microsoft Windows, Plan 9, MS-DOS, FreeDOS, OS/2, Atari TOS and AmigaOS. Ghostscript was originally written by L. Peter Deutsch for the GNU Project, with version 8.54 in 2006, both development branches were merged again, and dual-licensed releases were still provided. Ghostscript is currently owned by Artifex Software and maintained by Artifex Software employees, according to Artifex, as of version 9. Artifex point of view on aggregated software was challenged in court for MuPDF, in February 2013, Ghostscript changed its license from GPLv3 to GNU AGPL, which raised license compatibility questions for example by Debian. AGPL Ghostscript is the variant available, since February 2013. GNU Ghostscript is part of the GNU project and is now derived from GPL Ghostscript, ESP Ghostscript was distributed by Easy Software Products under the GPL. It was based on GPL Ghostscript and contains several modifications to improve compatibility with ESPs Common Unix Printing System and this version is no longer developed, since it was merged with GPL Ghostscript. Ghostscript is the current commercial proprietary version licensed by Artifex Software for inclusion in closed-source products, ghost Trap is a variant of GPL Ghostscript secured and sandboxed using Google Chromes sandbox technology. Aladdin Ghostscript was before June 2006 the leading edge of Ghostscript development, the GPL version is also used as the basis for a Display Ghostscript, which adds the functionality needed to fully support Display PostScript. Uses the libspectre library to render postscript, which in turn needs libgs from ghostscript, the current Windows package of Evince comes with libgs version 8. GSview runs under Microsoft Windows, OS/2, and Unix-like operating systems and it is best known in its Windows and OS/2 versions. On UNIX it uses the GTK+ toolkit, although released under Aladdin Free Public Licence, it also employs a nag screen to urge users to register so as to support the development of GSview
20.
Amiga
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The Amiga is a family of personal computers sold by Commodore in the 1980s and 1990s. The Amiga provided a significant upgrade from earlier 8-bit home computers, the Amiga 1000 was officially released in July 1985, but a series of production problems meant it did not become widely available until early 1986. The best selling model, the Amiga 500, was introduced in 1987 and became one of the home computers of the late 1980s. The A3000, introduced in 1990, started the second generation of Amiga systems, followed by the A500+, finally, as the third generation, the A1200 and the A4000 were released in late 1992. The platform became particularly popular for gaming and programming demos and it also found a prominent role in the desktop video, video production, and show control business, leading to video editing systems such as the Video Toaster. The Amigas native ability to play back multiple digital sound samples made it a popular platform for early tracker music software. It was also an expensive alternative to the Apple Macintosh. Initially, the Amiga was developed alongside various Commodore PC clones, Commodore ultimately went bankrupt in April 1994 after the Amiga CD32 model failed in the marketplace. Since the demise of Commodore, various groups have marketed successors to the original Amiga line, including Genesi, Eyetech, ACube Systems Srl, likewise, AmigaOS has influenced replacements, clones and compatible systems such as MorphOS, AmigaOS4 and AROS. The Amiga was so far ahead of its time that almost nobody—including Commodores marketing department—could fully articulate what it was all about. Today, its obvious the Amiga was the first multimedia computer, but in those days it was derided as a machine because few people grasped the importance of advanced graphics, sound. Nine years later, vendors are still struggling to make systems that work like 1985 Amigas, Jay Miner joined Atari in the 1970s to develop custom integrated circuits, and led development of the Atari 2600s TIA. Almost as soon as its development was complete, the team developing a much more sophisticated set of chips, CTIA, ANTIC and POKEY. With the 8-bit lines launch in 1979, Miner again started looking at a next generation chipset, Miner wanted to start work with the new Motorola 68000, but management was only interested in another MOS6502 based system. Miner left the company, and the industry, shortly thereafter, in 1982, Larry Kaplan was approached by a number of investors who wanted to develop a new game platform. Kaplan hired Miner to run the side of the newly formed company. The system was code-named Lorraine in keeping with Miners policy of giving systems female names, in case the company presidents wife. When Kaplan left the late in 1982 to rejoin Atari, Miner was promoted to head engineer
21.
Ubuntu (operating system)
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Ubuntu is published by Canonical Ltd, who offer commercial support. It uses Unity as its user interface for the desktop. Ubuntu is the most popular operating system running in hosted environments, so–called clouds, development of Ubuntu is led by UK-based Canonical Ltd. a company of South African entrepreneur Mark Shuttleworth. Canonical generates revenue through the sale of technical support and other related to Ubuntu. The Ubuntu project is committed to the principles of open-source software development, people are encouraged to use free software, study how it works, improve upon it. Ubuntu is built on Debians architecture and infrastructure, to provide Linux server, desktop, phone, tablet, the first release was in October 2004. Starting with Ubuntu 6.06, every release, one release every two years, receives long-term support. Long-term support includes updates for new hardware, security patches and updates to the Ubuntu stack. The first LTS releases were supported for three years on the desktop and five years on the server, since Ubuntu 12.04 LTS, LTS releases get regular point releases with support for new hardware and integration of all the updates published in that series to date. Ubuntu packages are based on packages from Debians unstable branch, both distributions use Debians deb package format and package management tools. Debian and Ubuntu packages are not necessarily compatible with each other, however. Many Ubuntu developers are also maintainers of key packages within Debian, Ubuntu cooperates with Debian by pushing changes back to Debian, although there has been criticism that this does not happen often enough. Ian Murdock, the founder of Debian, had expressed concern about Ubuntu packages potentially diverging too far from Debian to remain compatible, before release, packages are imported from Debian unstable continuously and merged with Ubuntu-specific modifications. One month before release, imports are frozen, and packagers then work to ensure that the frozen features interoperate well together, Ubuntu is currently funded by Canonical Ltd. On 8 July 2005, Mark Shuttleworth and Canonical announced the creation of the Ubuntu Foundation, the purpose of the foundation is to ensure the support and development for all future versions of Ubuntu. Mark Shuttleworth describes the goal as to ensure the continuity of the Ubuntu project. On 12 March 2009, Ubuntu announced developer support for 3rd-party cloud management platforms, Unity has become the default GUI for Ubuntu Desktop, although following the release of Ubuntu 17.10 it will move to the GNOME3 desktop instead as work on Unity ends. A default installation of Ubuntu contains a range of software that includes LibreOffice, Firefox, Thunderbird, Transmission
22.
Vaporware
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In the computer industry, vaporware is a product, typically computer hardware or software, that is announced to the general public but is never actually manufactured nor officially cancelled. Use of the word has broadened to include such as automobiles. Vaporware is often announced months or years before its purported release, developers have been accused of intentionally promoting vaporware to keep customers from switching to competing products that offer more features. Network World magazine called vaporware an epidemic in 1989, and blamed the press for not investigating whether developers claims were true, seven major companies issued a report in 1990 saying they felt vaporware had hurt the industrys credibility. The United States accused several companies of announcing vaporware early in violation of antitrust laws, infoWorld magazine wrote that the word is overused, and places an unfair stigma on developers. Vaporware was coined by a Microsoft engineer in 1982 to describe the companys Xenix operating system and it became popular among writers in the industry as a way to describe products they felt took too long to be released. InfoWorld magazine editor Stewart Alsop helped popularize it by lampooning Bill Gates with a Golden Vaporware award for the release of his companys first version of Windows in 1985. Vaporware, sometimes synonymous with vaportalk in the 1980s, has no single definition and it is generally used to describe a hardware or software product that has been announced, but that the developer has no intention of releasing any time soon, if ever. The first reported use of the word was in 1982 by an engineer at the software company Microsoft. Ann Winblad, president of Open Systems Accounting Software, wanted to know if Microsoft planned to stop developing its Xenix operating system as some of Open Systems products depended on it. She asked two Microsoft software engineers, John Ulett and Mark Ursino, who confirmed that development of Xenix had stopped, one of them told me, Basically, its vaporware, she later said. Winblad compared the word to the idea of selling smoke, implying Microsoft was selling a product it would not support. Winblad described the word to influential computer expert Esther Dyson, who published it for the first time in her monthly newsletter RELease 1.0. In an article titled Vaporware in the November 1983 issue of RELease 1.0 and she described three software products shown at COMDEX in Las Vegas that year with bombastic advertisements. She stated that demonstrations of the revolutions, breakthroughs and new generations at the exhibition did not meet those claims. The practice existed before Winblads account, in a January 1982 review of the new IBM Personal Computer, BYTE favorably noted that IBM refused to acknowledge the existence of any product that is not ready to be put on dealers shelves tomorrow. Although this is frustrating at times, it is a change from some companies practice of announcing a product even before its design is finished. Creative Computing in March 1984 wrote of Colecos delay in releasing the Adam that the company did not invent the practice of debuting products before they actually exist
23.
Bookmark
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A bookmark is a thin marker, commonly made of card, leather, or fabric, used to keep the readers place in a book and to enable the reader to return to it with ease. Other frequently used materials for bookmarks are paper, metals like silver and brass, silk, wood, cord, many bookmarks can be clipped on a page with the aid of a page-flap. According to new results of the research done on the history of bookmarks, the earliest existing bookmark dates from the 6th century AD and it is made of ornamented leather lined with vellum on the back and was attached with a leather strap to the cover of a Coptic codex. It was found near Sakkara, Egypt, under the ruins of the monastery Apa Jeremiah, further earliest bookmarks and remnants of them have been found in Coptic codices dating from the 1st to the 11th century and in Carolingian codices from the 8th to the 12th century. Bookmarks were used throughout the period, consisting usually of a small parchment strip attached to the edge of folio. As the first printed books were rare and valuable, it was determined early on that something was needed to mark ones place in a book without causing its pages any harm. Some of the earliest bookmarks were used at the end of the sixteenth century, modern bookmarks are available in a huge variety of materials in a multitude of designs and styles. The first detached, and therefore collectible, bookmarkers began to appear in the 1850s, one of the first references to these is found in Mary Russell Mitfords Recollections of a Literary Life, I had no marker and the richly bound volume closed as if instinctively. Note the abbreviation of bookmarker to marker, the modern abbreviation is usually bookmark. Historical bookmarks can be valuable, and are sometimes collected along with other paper ephemera. By the 1860s, attractive machine-woven markers were being manufactured, mainly in Coventry, England, one of the earliest was produced by J. &J. Cash to mark the death of Albert, Prince Consort, in 1861. Thomas Stevens of Coventry soon became pre-eminent in the field and claimed to have nine hundred different designs, woven pictorial bookmarks produced by Thomas Steven, a 19th-century English silk weaver, starting around 1862, are called Stevengraphs. Woven silk bookmarks were very appreciated gifts in the Victorian Era, most 19th-century bookmarks were intended for use in Bibles and prayer books and were made of ribbon, woven silk, or leather. By the 1880s the production of woven silk markers was declining and this development paralleled the wider availability of books themselves, and the range of available bookmarkers soon expanded dramatically. Bookmark Dog ears Rotating bookmark Earliest History of Bookmarks by Asim Maner World of Bookmarks, international Friends of Bookmarks, community website with lots of nformation about bookmarks
24.
Thumbnail
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Thumbnails are reduced-size versions of pictures or videos, used to help in recognizing and organizing them, serving the same role for images as a normal text index does for words. Some web designers produce thumbnails with HTML or client-side scripting that makes the users browser shrink the picture and this results in no saved bandwidth, and the visual quality of browser resizing is usually less than ideal. Displaying a significant part of the picture instead of the frame can allow the use of a smaller thumbnail while maintaining recognizability. For example, when thumbnailing a full-body portrait of a person, however, this may mislead the viewer about what the image contains, so is more suited to artistic presentations than searching or catalogue browsing. In 2002, the court in the US case Kelly v. Arriba Soft Corporation ruled that it was use for Internet search engines to use thumbnail images to help web users find what they seek. The word thumbnail is a reference to the thumbnail and alludes towards the small size of the image or picture. The word was then used figuratively, in noun and adjective form, to refer to anything small or concise, such as a biographical essay. The use of the thumbnail in the specific context of computer images as a small graphical representation, as of a larger graphic. The Denver Public Library Digitization and Cataloguing Program produces thumbnails that are 160 pixels in the long dimension, the California Digital Library Guidelines for Digital Images recommend 150-200 pixels for each dimension. Picture Australia requires thumbnails to be 150 pixels in the long dimension, the International Dunhuang Project Standards for Digitization and Image Management specifies a height of 96 pixels at 72 ppi. DeviantArt automatically produces thumbnails that are maximum 150 pixels in the long dimension, flickr automatically produces thumbnails that are a maximum 240 pixels in the long dimension, or smaller 75×75 pixels. It also applies unsharp mask to them, picasa automatically produces thumbnails that are a maximum 144 pixels in the long dimension, or 160×160 pixels album thumbnails. The term vignette is sometimes used to describe an image that is smaller than the original, larger than a thumbnail, thumbnail sketches are similar to doodles, but may include as much detail as a small sketch. Image organizer Contact print, a cognate of the thumbnail Thumbshots
25.
MetaPost
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MetaPost refers to both a programming language and the interpreter of the MetaPost programming language. Both are derived from Donald Knuths Metafont language and interpreter, MetaPost produces diagrams in the PostScript programming language from a geometric/algebraic description. The language shares Metafonts declarative syntax for manipulating lines, curves, points, the MetaPost language can include text labels on the diagrams, either strings from a specified font, or anything else that can be typeset with TeX. Many of the limitations of MetaPost derive from features of Metafont, moreover, MetaPost does not support all features of PostScript. Most notably, paths can have one segment, and regions can be filled only with uniform colours. PostScript level 1 supports tiled patterns and PostScript 3 supports Gouraud shading, to this end, the Asymptote graphics language has been developed to address these shortcomings. MetaPost is distributed with many distributions of the TeX and Metafont framework, in particular, it is included in the teTeX and the TeX Live distribution, common on Linux and Unix platforms. The encapsulated postscript produced by Metapost can be included in TeX, ConTeXt and this output can also be included in the PDFTeX dialect of TeX, thus directly giving PDF output from TeX. This ability is implemented in ConTeXt and in the LaTeX graphics package, ConTeXt even supports the creation of MetaPost files from within the TeX file. This is a single file example. mp which when processed by the MetaPost interpreter produces three eps files example.1, example.2, example.3 and these are pictured on the right. The resulting three eps files can be used in TeX via LaTeXs \includegraphics command, ConTeXts \externalfigure, Plain TeXs \epsfbox command, to view or print the third diagram, this inclusion is necessary, as the TeX fonts are not included in the eps files produced by MetaPost. Available as a file mpman. ps distributed with MetaPost, or from the Bell Labs web site, also available in PDF format from CTAN
26.
JPEG
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JPEG is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable tradeoff between size and image quality. JPEG typically achieves 10,1 compression with little loss in image quality. JPEG compression is used in a number of file formats. These format variations are not distinguished, and are simply called JPEG. The term JPEG is an initialism/acronym for the Joint Photographic Experts Group, the MIME media type for JPEG is image/jpeg, except in older Internet Explorer versions, which provides a MIME type of image/pjpeg when uploading JPEG images. JPEG files usually have an extension of. jpg or. jpeg. JPEG/JFIF supports a maximum size of 65, 535×65,535 pixels. JPEG stands for Joint Photographic Experts Group, the name of the committee created the JPEG standard. The Joint stood for ISO TC97 WG8 and CCITT SGVIII, in 1987 ISO TC97 became ISO/IEC JTC1 and in 1992 CCITT became ITU-T. Currently on the JTC1 side JPEG is one of two sub-groups of ISO/IEC Joint Technical Committee 1, Subcommittee 29, Working Group 1 – titled as Coding of still pictures, on the ITU-T side ITU-T SG16 is the respective body. The original JPEG group was organized in 1986, issuing the first JPEG standard in 1992, which was approved in September 1992 as ITU-T Recommendation T.81 and in 1994 as ISO/IEC 10918-1. The JPEG standard specifies the codec, which defines how an image is compressed into a stream of bytes and decompressed back into an image, the Exif and JFIF standards define the commonly used file formats for interchange of JPEG-compressed images. JPEG standards are formally named as Information technology – Digital compression, ISO/IEC10918 consists of the following parts, Ecma International TR/98 specifies the JPEG File Interchange Format, the first edition was published in June 2009. The JPEG compression algorithm is at its best on photographs and paintings of scenes with smooth variations of tone. For web usage, where the amount of used for an image is important. JPEG/Exif is also the most common format saved by digital cameras, on the other hand, JPEG may not be as well suited for line drawings and other textual or iconic graphics, where the sharp contrasts between adjacent pixels can cause noticeable artifacts. Such images may be saved in a lossless graphics format such as TIFF, GIF, PNG
27.
Portable Network Graphics
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Portable Network Graphics is a raster graphics file format that supports lossless data compression. PNG was created as an improved, non-patented replacement for Graphics Interchange Format, PNG supports palette-based images, grayscale images, and full-color non-palette-based RGB/RGBA images. PNG was designed for transferring images on the Internet, not for professional-quality print graphics, a PNG file contains a single image in an extensible structure of chunks, encoding the basic pixels and other information such as textual comments and integrity checks. PNG files nearly always use file extension PNG or png and are assigned MIME media type image/png, PNG was approved for this use by the Internet Engineering Steering Group on 14 October 1996, and was published as an ISO/IEC standard in 2004. In this thread, Oliver Fromme, author of the popular DOS JPEG viewer QPEG, proposed the PING name, meaning PING is not GIF, although GIF allows for animation, it was decided that PNG should be a single-image format. In 2001, the developers of PNG published the Multiple-image Network Graphics format, MNG achieved moderate application support, but not enough among mainstream web browsers and no usage among web site designers or publishers. In 2008, certain Mozilla developers published the Animated Portable Network Graphics format with similar goals,1 October 1996, Version 1.0 of the PNG specification was released, and later appeared as RFC2083. It became a W3C Recommendation on 1 October 1996,31 December 1998, Version 1.1, with some small changes and the addition of three new chunks, was released. 11 August 1999, Version 1.2, adding one extra chunk, was released,10 November 2003, PNG became an International Standard. This version of PNG differs only slightly from version 1.2, the original PNG specification was authored by an ad-hoc group of computer graphics experts and enthusiasts. Discussions and decisions about the format were done exclusively via email, a chunk consists of four parts, length, chunk type/name, chunk data and CRC. The CRC is a network-byte-order CRC-32 computed over the type and chunk data. Chunk types are given a case sensitive ASCII type/name, compare FourCC. The case of the different letters in the name is a bit field that provides the decoder with some information on the nature of chunks it does not recognize, the case of the first letter indicates whether the chunk is critical or not. If the first letter is uppercase, the chunk is critical, if not, critical chunks contain information that is necessary to read the file. If a decoder encounters a critical chunk it does not recognize, the case of the second letter indicates whether the chunk is public or private. Uppercase is public and lowercase is private and this ensures that public and private chunk names can never conflict with each other. The third letter must be uppercase to conform to the PNG specification and it is reserved for future expansion
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