machine

machine

[muh-sheen]
machine, arrangement of moving and stationary mechanical parts used to perform some useful work or to provide transportation. From a historical perspective, many of the first machines were the result of human efforts to improve war-making capabilities; the term engineer at one time had an exclusively military connotation. In the United States the original colonies were not permitted to make or import machine tools; it was only after the Revolution that the first manufacturing machines were built (c.1790) by Samuel Slater for a textile mill in Pawtucket, R.I.

Types of Machines

By means of a machine an applied force is increased, its direction is changed, or one form of motion or energy is changed into another form. Thus defined, such simple devices as the lever, the pulley, the inclined plane, the screw, and the wheel and axle are machines. They are called simple machines; more complicated machines are merely combinations of them. Of the five, the lever, the pulley, and the inclined plane are primary; the wheel and axle and the screw are secondary. The wheel and axle combination is a rotary lever, while the screw may be considered an inclined plane wound around a core. The wedge is a double inclined plane.

Complex machines are designated, as a rule, by the operations they perform; the complicated devices used for sawing, planing, and turning, for example, are known as sawing machines, planing machines, and turning machines respectively and as machine tools collectively. Machines used to transform other forms of energy (as heat) into mechanical energy are known as engines, i.e. the steam engine or the internal-combustion engine. The electric motor transforms electrical energy into mechanical energy. Its operation is the reverse of that of the electric generator, which transforms the energy of falling water or steam into electrical energy.

Mechanical Advantage and Efficiency of Machines

By means of a machine, a small force, or effort, can be applied to move a much greater resistance, or load. In doing so, however, the applied force must move through a much greater distance than it would if it could move the load directly. The mechanical advantage (MA) of a machine is the factor by which it multiplies any applied force. The MA may be calculated from the ratio of the forces involved or from the ratio of the distances through which they move. Ideally, the two ratios are equal, and it is simpler to calculate the ratio of the distance the effort moves to the distance the resistance moves; this is called the ideal mechanical advantage (IMA). In any real machine some of the effort is used to overcome friction. Thus, the ratio of the resistance force to the effort, called the actual mechanical advantage (AMA), is less than the IMA.

The efficiency of any machine measures the degree to which friction and other factors reduce the actual work output of the machine from its theoretical maximum. A frictionless machine would have an efficiency of 100%. A machine with an efficiency of 20% has an output only one fifth of its theoretical output. The efficiency of a machine is equal to the ratio of its output (resistance multiplied by the distance it is moved) to its input (effort multiplied by the distance through which it is exerted); it is also equal to the ratio of the AMA to the IMA. This does not mean that low-efficiency machines are of limited use. An automobile jack, for example, must overcome a great deal of friction and therefore has low efficiency, but it is extremely valuable because small effort can be applied to lift a great weight.

Although most machines are used to multiply an effort so that it may move a greater resistance, they may have other purposes. For example, a single, fixed pulley merely changes the direction of the applied force; the pulley may make it easier to lift the load, since a person can pull down on a rope, thus adding his or her own weight to the effort, rather than simply lifting the load. In a catapult an effort greater than the load moves through a short distance, causing the load to be moved through a large distance before being released. As the load is being moved, it picks up speed so that it is traveling at a considerable velocity when it leaves the catapult.

Machine from which various goods may be purchased, either with coin, paper currency, or electronic payment card. The first vending machines were introduced in 18th-century England to sell snuff and tobacco. From the late 19th century they have been widely used in many countries. Vending service is typically provided by a company that owns the machines and places them in businesses, schools, and the like. These operators provide the products and service either without cost to the owner of the premises on which a machine is located or in return for a servicing charge.

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Machine for stitching material (such as cloth or leather), usually having a needle and shuttle to carry thread and powered by treadle or electricity. Invented by Elias Howe in 1846 and successfully manufactured by Howe and Isaac Merritt Singer, it became the first widely distributed mechanical home appliance and has also been an important industrial machine. Modern sewing machines are usually powered by an electric motor, but the foot-treadle machine is still in wide use in much of the world.

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Machine tool for cutting up bars of material or for cutting out shapes in plates of raw material. The cutting tools (saws) may be thin metallic disks with teeth on their edges, thin metal blades or flexible bands with teeth on one edge, or thin grinding wheels. The tools may use any of three actions: true cutting, grinding, or friction-created melting.

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In U.S. politics, a political organization that controls enough votes to maintain political and administrative control of its community. The rapid growth of cities in the 19th century created huge problems for city governments, which were often poorly organized and unable to provide services. Enterprising politicians were able to win support by offering favours, including patronage jobs and housing, in exchange for votes. Though machines often helped to restructure city governments to the benefit of their constituents, they just as often resulted in poorer service (when jobs were doled out as political rewards), corruption (when contracts or concessions were awarded in return for kickbacks), and aggravation of racial or ethnic hostilities (when the machine did not reflect the city's diversity). Reforms, suburban flight, and a more mobile population with fewer ties to city neighbourhoods have weakened machine politics. Famous machines include those of William Magear Tweed (New York), James Michael Curley (Boston), Thomas Pendergast (Kansas City, Mo.), and Richard J. Daley (Chicago). Seealso civil service.

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Device for producing copies of text or graphic material by the use of light, heat, chemicals, or electrostatic charge. Most modern copiers use a method called xerography.

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Machine tool that rotates a circular tool with numerous cutting edges arranged symmetrically about its axis, called a milling cutter. The metal workpiece is usually held in a vise clamped to a table that can move in three perpendicular directions. Cutters of many shapes and sizes are available for a wide variety of milling operations. Milling machines cut flat surfaces, grooves, shoulders, inclined surfaces, dovetails, and T-slots. Various form-tooth cutters are used for cutting concave forms and convex grooves, for rounding corners, and for cutting gear teeth.

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Stationary, power-driven machine used to cut, shape, or form materials such as metal and wood. Machine tools date from the invention of the steam engine in the 18th century; most common machine tools were designed by the middle of the 19th century. Today dozens of different machine tools are used in the workshops of home and industry. They are frequently classified into seven types: turning machines such as lathes; shapers and planers; power drills or drill presses; milling machines; grinding machines; power saws; and presses (e.g., punch presses).

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Automatic weapon capable of rapid, sustained fire, usually 500–1,000 rounds per minute. Developed in the late 19th century by such inventors as Hiram Maxim, it profoundly altered modern warfare. The World War I battlefield was dominated by the belt-fed machine gun, which remained little changed into World War II. Modern machine guns are classified into three groups: the squad automatic weapon, chambered for small-calibre assault-rifle ammunition and operated by one soldier; the general-purpose machine gun, firing full-power rifle ammunition and operated by two; and the heavy machine gun, firing rounds of 12.7 mm (.5 in) or higher and often mounted on an armoured vehicle. Seealso submachine gun.

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Device that amplifies or replaces human or animal effort to accomplish a physical task. A machine may be further defined as a device consisting of two or more parts that transmit or modify force and motion in order to do work. The five simple machines are the lever, the wedge, the wheel and axle, the pulley, and the screw; all complex machines are combinations of these basic devices. The operation of a machine may involve the transformation of chemical, thermal, electrical, or nuclear energy into mechanical energy, or vice versa. All machines have an input, an output, and a transforming or modifying and transmitting device. Machines that receive their input energy from a natural source (such as air currents, moving water, coal, petroleum, or uranium) and transform it into mechanical energy are known as prime movers; examples include windmills, waterwheels, turbines, steam engines, and internal-combustion engines.

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Machine tool that uses a rotating abrasive grinding wheel to change the shape or dimensions of a hard, usually metallic, workpiece. Grinding is the most accurate of all the basic machining processes. All grinding machines use a wheel made from one of the manufactured abrasives, silicon carbide or aluminum oxide. To grind a cylindrical form, the workpiece rotates as it is fed against the grinding wheel. To grind an internal surface, a small wheel moves inside the hollow of the workpiece, which is gripped in a rotating chuck. On a surface grinder, the workpiece is held in place on a table that moves under the rotating abrasive wheel.

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or drilling machine

Machine tool for producing holes in hard substances. The drill is held in a rotating spindle and is fed into the workpiece, which is usually clamped in a vise supported on a table. The drill may be gripped in a chuck with three jaws that move radially in unison, or it may have a tapered shank that fits into a tapered hole in the spindle. Means are provided for varying the spindle speed and (on some machines) for automatically feeding the drill into the workpiece. Seealso boring machine.

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Machine tool, usually hydraulically operated, for finishing surfaces by drawing or pushing a cutter called a broach entirely over and past the surface. A broach has a series of cutting teeth arranged in a row or rows, graduated in height from the teeth that cut first to those that cut last. Each tooth removes only a few thousandths of an inch, and the total depth of cut is distributed over all the teeth. Broaching is particularly suitable for internal surfaces such as holes and internal gears, but it can also shape external gears and flat surfaces.

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Machine tool for producing smooth and accurate holes in a workpiece by enlarging existing holes with a cutting tool, which may bear a single tip of steel, cemented carbide, or diamond or may be a small grinding wheel. The hole's diameter is controlled by adjusting the boring head. Bored holes are more accurate in roundness, concentricity, and parallelism than drilled holes. Boring machines used in toolmaking shops have a vertical spindle and a work-holding table that moves horizontally in two perpendicular directions so that holes can be accurately spaced. In mass-production plants, boring machines with multiple spindles are common. Seealso drill; drill press; lathe.

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Hypothetical computing device proposed by Alan M. Turing (1936). Not actually a machine, it is an idealized mathematical model that reduces the logical structure of any computing device to its essentials. It consists of an infinitely extensible tape, a tape head that is capable of performing various operations on the tape, and a modifiable control mechanism in the head that can store instructions. As envisaged by Turing, it performs its functions in a sequence of discrete steps. His extrapolation of the essential features of information processing was instrumental in the development of modern digital computers, which share his basic scheme of an input/output device (tape and tape reader), central processing unit (CPU, or control mechanism), and stored memory.

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The Z-machine is a virtual machine that was developed by Joel Berez and Marc Blank in 1979 and used by Infocom for its text adventure games. Infocom compiled game code to files containing Z-machine instructions (called story files, or Z-code files), and could therefore port all its text adventures to a new platform simply by writing a Z-machine implementation for that platform. With the large number of incompatible home computer systems in use at the time, this was an important advantage over using native code (or developing some compiler for each system).

The "Z" of Z-machine stands for Zork, Infocom's first adventure game. Z-code files usually have names ending in .z1, .z2, .z3, .z4, .z5, .z6, .z7 or .z8, where the number is the version number of the Z-machine on which the file is intended to be run, as given by the first byte of the story file. This is a modern convention, however. Infocom itself used extensions of .dat (Data) and .zip (ZIP = Z-machine Interpreter Program), but the latter clashes with the present widespread use of .zip for PKZIP-compatible archive files (which did not exist yet during the time Infocom was active). Infocom produced six versions of the Z-machine. Files using versions 1 and 2 are very rare. Only two version 1 files are known to have been released by Infocom, and only two of version 2. Version 3 covers the vast majority of Infocom's released games. The later versions had more capabilities, culminating in some graphic support in version 6.

The compiler (called Zilch) which Infocom used to produce its story files has never been released, although documentation of the language used (called ZIL, for Zork Implementation Language) still exists. But in May 1993, Graham Nelson released the first version of his Inform compiler, which also generates Z-machine story files as its output, even though the Inform source language is quite different from ZIL. Most files produced by Inform are version 5.

Inform has since become very popular in the interactive fiction community and, as a consequence, a large proportion of the interactive fiction now produced is in the form of Z-machine story files. Demand for the ability to create larger game files led Graham Nelson to specify versions 7 and 8 of the Z-machine, though version 7 is very rarely used. Because of the way addresses are handled, a version 3 story file can be up to 128K in length, a version 5 story can be up to 256K in length, and a version 8 story can be up to 512k in length. Though these sizes may seem small by today's computing standards, for text-only adventures, these are large enough for very elaborate games.

During the 1990s, Graham Nelson drew up a Z-machine standard, based on detailed studies of the existing Infocom files.

Interpreters

Interpreters for Z-code files are available on such a wide variety of platforms - for example, on various old machines (such as the Apple II, TRS-80 and Sinclair), portable machines (such as Palm OS devices and the Nintendo Game Boy) and most modern platforms, showing that it is a very portable language.

Popular interpreters include Nitfol and Frotz. Nitfol makes use of the Glk API, and supports versions 1 through 8 of the Z-machine, including the version 6 graphical Z-machine. Save files are stored in the standard Quetzal save format. Binary files are currently available for several different operating systems, including Macintosh, Linux, MS-DOS, and Windows.

Frotz

Frotz is a Z-machine implementation: an adventure game engine for playing the Infocom's text adventures, as well as more recent games released by others.

Frotz is perhaps the most well-known and popular Z-machine implementation available. Its advantages over other Z-machine interpreters are twofold: firstly, though it was not the first non-Infocom interpreter to be released, it was one of the early ones -- its initial release by Stefan Jokisch was in 1995. Secondly, because the program is written in highly portable C, it has been possible to port the original DOS version to most modern computer formats, including not only Unix and Windows but even palmtops and mobile phones. Various extensions have since been added, such as sound effects and graphics.

In 2002, the Frotz core codebase was picked up by David Griffith, who continues to develop it. The codebase was then distinctly split between the virtual machine and the user interface portions such that the virtual machine became entirely independent from any user interface. This allowed some clever programmers to create some of the stranger ports of Frotz. One of the strangest is also one of the simplest: an instant messenger bot is wrapped around a version of Frotz with the bare minimum of IO functionality creating a bot with which one can play most Z-machine games using an instant messenger.

Other utilities

ZorkTools is a collection of utility programs which provide capabilities not normally available for Z-code story files, such as listing all objects or vocabulary words.

See also

  • Glulx - Similar to the Z-machine, but relieves several legacy limitations.
  • SCUMM - Script Creation Utility for Maniac Mansion by LucasArts, a graphical system similar to Z-machine

External links

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