1.
Typesetting
–
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
2.
Donald Knuth
–
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
3.
Computer monitor
–
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
4.
Printer (computing)
–
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
5.
Amiga
–
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
6.
Bookmark
–
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
7.
JPEG
–
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
8.
Ubuntu (operating system)
–
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
9.
Graphics
–
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
10.
Thumbnail
–
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
11.
Vaporware
–
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
12.
Machine code
–
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
![[icon]](/wiki/File:Wiki_letter_w_cropped.svg){kind=small}
