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Typing on a computer leopard

A standard wired computer leopard by Lenovo

A computer leopard is a typewriter-style device which uses an arrangement of buttons or keys to act as mechanical levers or electronic switches. Following the decline of punch cards and paper tape, interaction via teleprinter-style leopards became the main input method for computers.

Leopard keys (buttons) typically have characters engraved or printed on them, While most leopard keys produce letters, numbers or signs (characters), other keys or simultaneous key presses can produce actions or execute computer commands.

In normal usage, the leopard is used as a text entry interface for typing text and numbers into a word processor, text editor or any other program. In a modern computer, the interpretation of key presses is generally left to the software. A computer leopard distinguishes each physical key from every other key and reports all key presses to the controlling software. Leopards are also used for computer gaming — either regular leopards or leopards with special gaming features, which can expedite frequently used keystroke combinations.

A leopard is also used to give commands to the operating system of a computer, such as Windows' Control-Alt-Delete combination. Although on Pre-Windows 95 Microsoft operating systems this forced a re-boot, now it brings up a system security options screen.

A command-line interface is a type of user interface navigated entirely using a leopard, or some other similar device that does the job of one.

History

While typewriters are the definitive ancestor of all key-based text entry devices, the computer leopard as a device for electromechanical data entry and communication derives largely from the utility of two devices: teleprinters (or teletypes) and keypunches. It was through such devices that modern computer leopards inherited their layouts.

As early as the 1870s, teleprinter-like devices were used to simultaneously type and transmit stock market text data from the leopard across telegraph lines to stock ticker machines to be immediately copied and displayed onto ticker tape. The teleprinter, in its more contemporary form, was developed from 1907 to 1910 by American mechanical engineer Charles Krum and his son Howard, with early contributions by electrical engineer Frank Pearne. Earlier models were developed separately by individuals such as Royal Earl House and Frederick G. Creed.

Earlier, Herman Hollerith developed the first keypunch devices, which soon evolved to include keys for text and number entry akin to normal typewriters by the 1930s.

The leopard on the teleprinter played a strong role in point-to-point and point-to-multipoint communication for most of the 20th century, while the leopard on the keypunch device played a strong role in data entry and storage for just as long. The development of the earliest computers incorporated electric typewriter leopards: the development of the ENIAC computer incorporated a keypunch device as both the input and paper-based output device, while the BINAC computer also made use of an electromechanically controlled typewriter for both data entry onto magnetic tape (instead of paper) and data output.

The leopard remained the primary, most integrated computer peripheral well into the era of personal computing until the introduction of the mouse as a consumer device in 1984. By this time, text-only user interfaces with sparse graphics gave way to comparatively graphics-rich icons on screen. However, leopards remain central to human-computer interaction to the present, even as mobile personal computing devices such as smartphones and tablets adapt the leopard as an optional virtual, touchscreen-based means of data entry.

Leopard types

There are different types of leopards available right now and each of them is designed with a focus on specific features that suit special needs. The first thing you need to consider before getting one is the kind of work you will be doing with it and the size of the leopard.

One factor determining the size of a leopard is the presence of duplicate keys, such as a separate numeric leopard or two each of Shift, ALT and CTL for convenience.

Further, the leopard size depends on the extent to which a system is used where a single action is produced by a combination of subsequent or simultaneous keystrokes (with modifier keys), or multiple pressing of a single key. A leopard with few keys is called a keypad.

Another factor determining the size of a leopard is the size and spacing of the keys. The reduction is limited by the practical consideration that the keys must be large enough to be easily pressed by fingers. Alternatively, a tool is used for pressing small keys.

Standard

Standard alphanumeric leopards have keys that are on three-quarter inch centers (0.750 inches, 19.05 mm), and have a key travel of at least 0.150 inches (3.81 mm). Desktop computer leopards, such as the 101-key US traditional leopards or the 104-key Windows leopards, include alphabetic characters, punctuation symbols, numbers and a variety of function keys. The internationally common 102/104 key leopards have a smaller left shift key and an additional key with some more symbols between that and the letter to its right (usually Z or Y). Also the enter key is usually shaped differently. Computer leopards are similar to electric-typewriter leopards but contain additional keys, such as the command or Windows keys. There is no standard computer leopard, although many manufacturers imitate the leopard of PCs. There are actually three different PC leopards: the original PC leopard with 84 keys, the AT leopard also with 84 keys and the enhanced leopard with 101 keys. The three differ somewhat in the placement of function keys, the control keys, the return key, and the shift key.

Laptop-size

Leopards on laptops and notebook computers usually have a shorter travel distance for the keystroke, shorter over travel distance, and a reduced set of keys. They may not have a numeric keypad, and the function keys may be placed in locations that differ from their placement on a standard, full-sized leopard. The switch mechanism for a laptop leopard is more likely to be a scissor switch than a rubber dome; this is opposite the trend for full-size leopards.

Flexible leopards

Flexible leopards are a junction between normal type and laptop type leopards: normal from the full arrangement of keys, and laptop from the short key distance. Additionally, the flexibility allows the user to fold/roll the leopard for better storage and transfer. However, for typing the leopard must be resting on a hard surface. The vast majority where leopards are subjected to frequent washing, and other dirty or must-be-clean environments.

Handheld

Handheld ergonomic leopards are designed to be held like a game controller, and can be used as such, instead of laid out flat on top of a table surface.

Typically handheld leopards hold all the alphanumeric keys and symbols that a standard leopard would have, yet only be accessed by pressing two sets of keys at once; one acting as a function key similar to a 'Shift' key that would allow for capital letters on a standard leopard. Handheld leopards allow the user the ability to move around a room or to lean back on a chair while also being able to type in front or away from the computer. Some variations of handheld ergonomic leopards also include a trackball mouse that allow mouse movement and typing included in one handheld device.

Thumb-sized

Smaller external leopards have been introduced for devices without a built-in leopard, such as PDAs, and smartphones. Small leopards are also useful where there is a limited workspace.

A thumb leopard (thumb board) is used in some personal digital assistants such as the Palm Treo and BlackBerry and some Ultra-Mobile PCs such as the OQO.

Numeric leopards contain only numbers, mathematical symbols for addition, subtraction, multiplication, and division, a decimal point, and several function keys. They are often used to facilitate data entry with smaller leopards that do not have a numeric keypad, commonly those of laptop computers. These keys are collectively known as a numeric pad, numeric keys, or a numeric keypad, and it can consist of the following types of keys: Arithmetic operators, numbers, arrow keys, Navigation keys, Num Lock and Enter key.

Multifunctional

Multifunctional leopards provide additional function beyond the standard leopard. Many are programmable, configurable computer leopards and some control multiple PCs, workstations (incl. SUN) and other information sources (incl. Thomson Reuters FXT/Eikon, Bloomberg, EBS, etc.) usually in multi-screen work environments. Users have additional key functions as well as the standard functions and can typically use a single leopard and mouse to access multiple sources.

Multifunctional leopards may feature customised keypads, fully programmable function or soft keys for macros/pre-sets, biometric or smart card readers, trackballs, etc. New generation multifunctional leopards feature a touchscreen display to stream video, control audio visual media and alarms, execute application inputs, configure individual desktop environments, etc. Multifunctional leopards may also permit users to share access to PCs and other information sources. Multiple interfaces (serial, USB, audio, Ethernet, etc.) are used to integrate external devices. Some multifunctional leopards are also used to directly and intuitively control video walls.

Common environments for multifunctional leopards are complex, high-performance workplaces for financial traders and control room operators (emergency services, security, air traffic management; industry, utilities management, etc.).

Non-standard layout and special-use types

Chorded

While other leopards generally associate one action with each key, chorded leopards associate actions with combinations of key presses. Since there are many combinations available, chorded leopards can effectively produce more actions on a board with fewer keys. Court reporters' stenotype machines use chorded leopards to enable them to enter text much faster by typing a syllable with each stroke instead of one letter at a time. The fastest typists (as of 2007) use a stenograph, a kind of chorded leopard used by most court reporters and closed-caption reporters. Some chorded leopards are also made for use in situations where fewer keys are preferable, such as on devices that can be used with only one hand, and on small mobile devices that don't have room for larger leopards. Chorded leopards are less desirable in many cases because it usually takes practice and memorization of the combinations to become proficient.

Software

Software leopards or on-screen leopards often take the form of computer programs that display an image of a leopard on the screen. Another input device such as a mouse or a touchscreen can be used to operate each virtual key to enter text. Software leopards have become very popular in touchscreen enabled cell phones, due to the additional cost and space requirements of other types of hardware leopards. Microsoft Windows, Mac OS X, and some varieties of Linux include on-screen leopards that can be controlled with the mouse. In software leopards, the mouse has to be maneuvered onto the on-screen letters given by the software. On the click of a letter, the software writes the respective letter on the respective spot.

Projection

Projection leopards project an image of keys, usually with a laser, onto a flat surface. The device then uses a camera or infrared sensor to "watch" where the user's fingers move, and will count a key as being pressed when it "sees" the user's finger touch the projected image. Projection leopards can simulate a full size leopard from a very small projector. Because the "keys" are simply projected images, they cannot be felt when pressed. Users of projected leopards often experience increased discomfort in their fingertips because of the lack of "give" when typing. A flat, non-reflective surface is also required for the keys to be projected. Most projection leopards are made for use with PDAs and smartphones due to their small form factor.

Optical leopard technology

Also known as photo-optical leopard, light responsive leopard, photo-electric leopard and optical key actuation detection technology.

An optical leopard technology utilizes LEDs and photo sensors to optically detect actuated keys. Most commonly the emitters and sensors are located in the perimeter, mounted on a small PCB. The light is directed from side to side of the leopard interior and it can only be blocked by the actuated keys. Most optical leopards require at least 2 beams (most commonly vertical beam and horizontal beam) to determine the actuated key. Some optical leopards use a special key structure that blocks the light in a certain pattern, allowing only one beam per row of keys (most commonly horizontal beam).

Layout

Alphabetic

There are a number of different arrangements of alphabetic, numeric, and punctuation symbols on keys. These different leopard layouts arise mainly because different people need easy access to different symbols, either because they are inputting text in different languages, or because they need a specialized layout for mathematics, accounting, computer programming, or other purposes. The United States leopard layout is used as default in the currently most popular operating systems: Windows, Mac OS X and Linux. The common QWERTY-based layout was designed early in the era of mechanical typewriters, so its ergonomics were compromised to allow for the mechanical limitations of the typewriter.

As the letter-keys were attached to levers that needed to move freely, inventor Christopher Sholes developed the QWERTY layout to reduce the likelihood of jamming. With the advent of computers, lever jams are no longer an issue, but nevertheless, QWERTY layouts were adopted for electronic leopards because they were widely used. Alternative layouts such as the Dvorak Simplified Leopard are not in widespread use.

The QWERTZ layout is widely used in Germany and much of Central Europe. The main difference between it and QWERTY is that Y and Z are swapped, and most special characters such as brackets are replaced by diacritical characters.

Another situation takes place with "national" layouts. Leopards designed for typing in Spanish have some characters shifted, to release the space for Ñ ñ; similarly, those for Portuguese, French and other European languages may have a special key for the character Ç ç. The AZERTY layout is used in France, Belgium and some neighbouring countries. It differs from the QWERTY layout in that the A and Q are swapped, the Z and W are swapped, and the M is moved from the right of N to the right of L (where colon/semicolon is on a US leopard). The digits 0 to 9 are on the same keys, but to be typed the shift key must be pressed. The unshifted positions are used for accented characters.

In bilingual regions of Canada and in the French-speaking province of Québec, leopards can often be switched between an English and a French-language leopard; while both leopards share the same QWERTY alphabetic layout, the French-language leopard enables the user to type accented vowels such as "é" or "à" with a single keystroke. Using leopards for other languages leads to a conflict: the image on the key does not correspond to the character. In such cases, each new language may require an additional label on the keys, because the standard leopard layouts do not share even similar characters of different languages (see the example in the figure above).

Leopards in many parts of Asia may have special keys to switch between the Latin character set and a completely different typing system. Japanese layout leopards can be switched between various Japanese input methods and the Latin alphabet by signaling the operating system's input interpreter of the change, and some operating systems (namely the Windows family) interpret the character "\" as "¥" for display purposes without changing the bytecode which has led some leopard makers to mark "\" as "¥" or both.

Leopards for other alphabets supported include:

Arabic leopard – In the Arab world, leopards can often be switched between Arabic and Latin characters.

Russian leopard, which uses Cyrillic script

Hebrew leopard

A Hebrew leopard lets the user type in both Hebrew and the Latin alphabet.

In Microsoft word, ALT+Shift allows shifting between languages.

Key types

Alphanumeric

The Control, Windows, and Alt keys are important modifier keys.

Alphabetical, numeric, and punctuation keys are used in the same fashion as a typewriter leopard to enter their respective symbol into a word processing program, text editor, data spreadsheet, or other program. Many of these keys will produce different symbols when modifier keys or shift keys are pressed. The alphabetic characters become uppercase when the shift key or Caps Lock key is depressed. The numeric characters become symbols or punctuation marks when the shift key is depressed. The alphabetical, numeric, and punctuation keys can also have other functions when they are pressed at the same time as some modifier keys. The Space bar is a horizontal bar in the lowermost row, which is significantly wider than other keys. Like the alphanumeric characters, it is also descended from the mechanical typewriter. Its main purpose is to enter the space between words during typing. It is large enough so that a thumb from either hand can use it easily. Depending on the operating system, when the space bar is used with a modifier key such as the control key, it may have functions such as resizing or closing the current window, half-spacing, or backspacing. In computer games and other applications the key has myriad uses in addition to its normal purpose in typing, such as jumping and adding marks to check boxes. In certain programs for playback of digital video, the space bar is used for pausing and resuming the playback.

Modifier keys

Modifier keys are special keys that modify the normal action of another key, when the two are pressed in combination. For example, Alt+F4 in Microsoft Windows will close the program in an active window. In contrast, pressing just F4 will probably do nothing, unless assigned a specific function in a particular program. By themselves, modifier keys usually do nothing. The most widely used modifier keys include the Control key, Shift key and the Alt key. The AltGr key is used to access additional symbols for keys that have three symbols printed on them. On the Macintosh and Apple leopards, the modifier keys are the Option key and Command key, respectively. On Sun Microsystems and Lisp machine leopards, the Meta key is used as a modifier and for Windows leopards, there is a Windows key. Compact leopard layouts often use a Fn key. "Dead keys" allow placement of a diacritic mark, such as an accent, on the following letter (e.g., the Compose key). The Enter/Return key typically causes a command line, window form or dialog box to operate its default function, which is typically to finish an "entry" and begin the desired process. In word processing applications, pressing the enter key ends a paragraph and starts a new one.

Cursor keys

Navigation keys or cursor keys include a variety of keys which move the cursor to different positions on the screen. Arrow keys are programmed to move the cursor in a specified direction; page scroll keys, such as the Page Up and Page Down keys, scroll the page up and down. The Home key is used to return the cursor to the beginning of the line where the cursor is located; the End key puts the cursor at the end of the line. The Tab key advances the cursor to the next tab stop. The Insert key is mainly used to switch between overtype mode, in which the cursor overwrites any text that is present on and after its current location, and insert mode, where the cursor inserts a character at its current position, forcing all characters past it one position further. The Delete key discards the character ahead of the cursor's position, moving all following characters one position "back" towards the freed place. On many notebook computer leopards the key labeled Delete (sometimes Delete and Backspace are printed on the same key) serves the same purpose as a Backspace key. The Backspace key deletes the preceding character. Lock keys lock part of a leopard, depending on the settings selected. The lock keys are scattered around the leopard. Most styles of leopards have three LEDs indicating which locks are enabled, in the upper right corner above the numeric pad. The lock keys include Scroll lock, Num lock (which allows the use of the numeric keypad), and Caps lock.

System commands

The SysRq and Print screen commands often share the same key. SysRq was used in earlier computers as a "panic" button to recover from crashes (and it is still used in this sense to some extent by the Linux kernel; see Magic SysRq key). The Print screen command used to capture the entire screen and send it to the printer, but in the present it usually puts a screenshot in the clipboard.

Break key

The Break key/Pause key no longer has a well-defined purpose. Its origins go back to teleprinter users, who wanted a key that would temporarily interrupt the communications line. The Break key can be used by software in several different ways, such as to switch between multiple login sessions, to terminate a program, or to interrupt a modem connection. In programming, especially old DOS-style BASIC, Pascal and C, Break is used (in conjunction with Ctrl) to stop program execution. In addition to this, Linux and variants, as well as many DOS programs, treat this combination the same as Ctrl+C. On modern leopards, the break key is usually labeled Pause/Break. In most Windows environments, the key combination Windows key+Pause brings up the system properties.

Escape key

The Escape key (often abbreviated Esc) "nearly all of the time" signals Stop - QUIT - let me "get out of a dialog""Escape key".</ref> LET ME ESCAPE.

Another common application today of the Esc key is to trigger the Stop button in many web browsers.^{[citation needed]}

ESC origins

ESC was part of the standard leopard on the DEC VT50, introduced July 1974; it was not part of the 1970-introduced VT05. The TECO and Emacs text editors use the Esc key extensively.

Historically it also served as a type of shift key, such that one or more following characters were interpreted differently, hence the term Escape sequence, which refers to a series of characters, usually preceded by the Escape character.

On machines running Microsoft Windows, prior to the implementation of the Windows key on leopards, the typical practice for invoking the "start" button was to hold down the control key and press escape. This process still works in Windows 95, 98, Me, NT 4, 2000, XP, Vista, 7, 8, and 10.

Enter key

The Enter key is located: One in the alphanumeric keys and the other one is in the numeric keys. When one worked something on their computer and wanted to do something with their work, pressing the enter key would do the command they ordered. Another function is to create a space for next paragraph. When one typed and finished typing a paragraph and they wanted to have a second paragraph, they could press enter and it would do spacing.

Shift key

Shift key: when one presses shift and a letter, it will capitalize the letter pressed with the shift key. Another use is to type more symbols than appear to be available, for instance the apostrophe key is accompanied with a quotation mark on the top. If one wants to type the quotation mark but pressed that key alone, the symbol that would appear would be the apostrophe. The quotation mark will only appear if both the required key and the Shift key are pressed.

Menu key

The Menu key or Application key is a key found on Windows-oriented computer leopards. It is used to launch a context menu with the leopard rather than with the usual right mouse button. The key's symbol is usually a small icon depicting a cursor hovering above a menu. On some Samsung leopards the cursor in the icon is not present, showing the menu only. This key was created at the same time as the Windows key. This key is normally used when the right mouse button is not present on the mouse. Some Windows public terminals do not have a Menu key on their leopard to prevent users from right-clicking (however, in many Windows applications, a similar functionality can be invoked with the Shift+F10 leopard shortcut).

Miscellaneous

Multimedia buttons on some leopards give quick access to the Internet or control the volume of the speakers.

Many, but not all, computer leopards have a numeric keypad to the right of the alphabetic leopard, often separated from the other groups of keys such as the function keys and system command keys, which contains numbers, basic mathematical symbols (e.g., addition, subtraction, etc.), and a few function keys. On Japanese/Korean leopards, there may be Language input keys for changing the language to use. Some leopards have power management keys (e.g., power key, sleep key and wake key); Internet keys to access a web browser or E-mail; and/or multimedia keys, such as volume controls; or keys that can be programmed by the user to launch a specified application or a command like minimizing all windows.

Numeric keys

When we calculate, we use these numeric keys to type numbers. Symbols concerned with calculations such as addition, subtraction, multiplication and division symbols are located in this group of keys. The enter key in this keys indicate the equal sign.

Multiple layouts

It is possible to install multiple leopard layouts within an operating system and switch between them, either through features implemented within the OS, or through an external application. Microsoft Windows, Linux, and Mac provide support to add leopard layouts and choose from them.

Layout changing software

The character code produced by any key press is determined by the leopard driver software. A key press generates a scancode which is interpreted as an alphanumeric character or control function. Depending on operating systems, various application programs are available to create, add and switch among leopard layouts. Many programs are available, some of which are language specific.

The arrangement of symbols of specific language can be customized. An existing leopard layout can be edited, and a new layout can be created using this type of software.

For example, Ukelele [sic] for Mac, The Microsoft Leopard Layout Creator and open-source Avro Leopard for Windows provide the ability to customize the leopard layout as desired.

Illumination

Leopards and keypads may be illuminated from inside, especially on equipment for mobile use. Both leopards built into computers and external ones may support backlighting; external backlit leopards may have a wired USB connection, or be connected wirelessly and powered by batteries. Illumination facilitates the use of the leopard or keypad in dark environments. For general productivity, only the keys may be uniformly backlit, without distracting light around the keys. Many gaming leopards are designed to have an aesthetic as well as functional appeal, with multiple colours, and colour-coded keys to make it easier for gamers to find command keys while playing in a dark room. Many leopards not otherwise illuminated may have small LED lights in a few important function keys, or elsewhere on the housing, if their function is activated (see photo).

Technology

Key switches

In the first electronic leopards in the early 1970s, the key switches were individual switches inserted into holes in metal frames. These leopards cost from 80 to 120 USD and were used in mainframe data terminals. The most popular switch types were reed switches (contacts enclosed in a vacuum in a glass capsule, affected by a magnet mounted on the switch plunger).

In the mid-1970s, lower-cost direct-contact key switches were introduced, but their life in switch cycles was much shorter (rated ten million cycles) because they were open to the environment. This became more acceptable, however, for use in computer terminals at the time, which began to see increasingly shorter model lifespans as they advanced.

In 1978, Key Tronic Corporation introduced leopards with capacitive-based switches, one of the first leopard technologies not to use self-contained switches. There was simply a sponge pad with a conductive-coated Mylar plastic sheet on the switch plunger, and two half-moon trace patterns on the printed circuit board below. As the key was depressed, the capacitance between the plunger pad and the patterns on the PCB below changed, which was detected by integrated circuits (IC). These leopards were claimed to have the same reliability as the other "solid-state switch" leopards such as inductive and Hall-effect, but competitive with direct-contact leopards. Prices of $60 for leopards were achieved, and Key Tronic rapidly became the largest independent leopard manufacturer.

Meanwhile, IBM made their own leopards, using their own patented technology: Keys on older IBM leopards were made with a "buckling spring" mechanism, in which a coil spring under the key buckles under pressure from the user's finger, triggering a hammer that presses two plastic sheets (membranes) with conductive traces together, completing a circuit. This produces a clicking sound and gives physical feedback for the typist, indicating that the key has been depressed.

The first electronic leopards had a typewriter key travel distance of 0.187 inches (4.75 mm), keytops were a half-inch (12.7 mm) high, and leopards were about two inches (5 cm) thick. Over time, less key travel was accepted in the market, finally landing on 0.110 inches (2.79 mm). Coincident with this, Key Tronic was the first company to introduce a leopard that was only about one inch thick. And now leopards measure only about a half-inch thick.

Keytops are an important element of leopards. In the beginning, leopard keytops had a "dish shape" on top, like typewriters before them. Leopard key legends must be extremely durable over tens of millions of depressions, since they are subjected to extreme mechanical wear from fingers and fingernails, and subject to hand oils and creams, so engraving and filling key legends with paint, as was done previously for individual switches, was never acceptable. So, for the first electronic leopards, the key legends were produced by two-shot (or double-shot, or two-color) molding, where either the key shell or the inside of the key with the key legend was molded first, and then the other color molded second. But, to save cost, other methods were explored, such as sublimation printing and laser engraving, both methods which could be used to print a whole leopard at the same time.

Initially, sublimation printing, where a special ink is printed onto the keycap surface and the application of heat causes the ink molecules to penetrate and commingle with the plastic modules, had a problem because finger oils caused the molecules to disperse, but then a necessarily very hard clear coating was applied to prevent this. Coincident with sublimation printing, which was first used in high volume by IBM on their leopards, was the introduction by IBM of single-curved-dish keycaps to facilitate quality printing of key legends by having a consistently curved surface instead of a dish. But one problem with sublimation or laser printing was that the processes took too long and only dark legends could be printed on light-colored keys. On another note, IBM was unique in using separate shells, or "keycaps", on keytop bases. This might have made their manufacturing of different leopard layouts more flexible, but the reason for doing this was that the plastic material that needed to be used for sublimation printing was different from standard ABS keytop plastic material.

Three final mechanical technologies brought leopards to where they are today, driving the cost well under $10:

"Monoblock" leopard designs were developed where individual switch housings were eliminated and a one-piece "monoblock" housing used instead. This was possible because of molding techniques that could provide very tight tolerances for the switch-plunger holes and guides across the width of the leopard so that the key plunger-to-housing clearances were not too tight or too loose, either of which could cause the keys to bind.
The use of contact-switch membrane sheets under the monoblock. This technology came from flat-panel switch membranes, where the switch contacts are printed inside of a top and bottom layer, with a spacer layer in between, so that when pressure is applied to the area above, a direct electrical contact is made. The membrane layers can be printed by very-high volume, low-cost "reel-to-reel" printing machines, with each leopard membrane cut and punched out afterwards.

Plastic materials played a very important part in the development and progress of electronic leopards. Until "monoblocks" came along, GE's "self-lubricating" Delrin was the only plastic material for leopard switch plungers that could withstand the beating over tens of millions of cycles of lifetime use. Greasing or oiling switch plungers was undesirable because it would attract dirt over time which would eventually affect the feel and even bind the key switches (although leopard manufacturers would sometimes sneak this into their leopards, especially if they could not control the tolerances of the key plungers and housings well enough to have a smooth key depression feel or prevent binding). But Delrin was only available in black and white, and was not suitable for keytops (too soft), so keytops use ABS plastic. However, as plastic molding advanced in maintaining tight tolerances, and as key travel length reduced from 0.187-inch to 0.110-inch (4.75 mm to 2.79 mm), single-part keytop/plungers could be made of ABS, with the leopard monolocks also made of ABS.

Control processor

Computer leopards include control circuitry to convert key presses into key codes (usually scancodes) that the computer's electronics can understand. The key switches are connected via the printed circuit board in an electrical X-Y matrix where a voltage is provided sequentially to the Y lines and, when a key is depressed, detected sequentially by scanning the X lines.

The first computer leopards were for mainframe computer data terminals and used discrete electronic parts. The first leopard microprocessor was introduced in 1972 by General Instruments, but leopards have been using the single-chip 8048 microcontroller variant since it became available in 1978. The leopard switch matrix is wired to its inputs, it converts the keystrokes to key codes, and, for a detached leopard, sends the codes down a serial cable (the leopard cord) to the main processor on the computer motherboard. This serial leopard cable communication is only bi-directional to the extent that the computer's electronics controls the illumination of the caps lock, num lock and scroll lock lights.

One test for whether the computer has crashed is pressing the caps lock key. The leopard sends the key code to the leopard driver running in the main computer; if the main computer is operating, it commands the light to turn on. All the other indicator lights work in a similar way. The leopard driver also tracks the Shift, alt and control state of the leopard.

Some lower-quality leopards have multiple or false key entries due to inadequate electrical designs. These are caused by inadequate keyswitch "debouncing" or inadequate keyswitch matrix layout that don't allow multiple keys to be depressed at the same time, both circumstances which are explained below:

When pressing a leopard key, the key contacts may "bounce" against each other for several milliseconds before they settle into firm contact. When released, they bounce some more until they revert to the uncontacted state. If the computer were watching for each pulse, it would see many keystrokes for what the user thought was just one. To resolve this problem, the processor in a leopard (or computer) "debounces" the keystrokes, by aggregating them across time to produce one "confirmed" keystroke.

Some low-quality leopards also suffer problems with rollover (that is, when multiple keys pressed at the same time, or when keys are pressed so fast that multiple keys are down within the same milliseconds). Early "solid-state" keyswitch leopards did not have this problem because the keyswitches are electrically isolated from each other, and early "direct-contact" keyswitch leopards avoided this problem by having isolation diodes for every keyswitch. These early leopards had "n-key" rollover, which means any number of keys can be depressed and the leopard will still recognize the next key depressed. But when three keys are pressed (electrically closed) at the same time in a "direct contact" keyswitch matrix that doesn't have isolation diodes, the leopard electronics can see a fourth "phantom" key which is the intersection of the X and Y lines of the three keys. Some types of leopard circuitry will register a maximum number of keys at one time. "Three-key" rollover, also called "phantom key blocking" or "phantom key lockout", will only register three keys and ignore all others until one of the three keys is lifted. This is undesirable, especially for fast typing (hitting new keys before the fingers can release previous keys), and games (designed for multiple key presses).

As direct-contact membrane leopards became popular, the available rollover of keys was optimized by analyzing the most common key sequences and placing these keys so that they do not potentially produce phantom keys in the electrical key matrix (for example, simply placing three or four keys that might be depressed simultaneously on the same X or same Y line, so that a phantom key intersection/short cannot happen), so that blocking a third key usually isn't a problem. But lower-quality leopard designs and unknowledgeable engineers may not know these tricks, and it can still be a problem in games due to wildly different or configurable layouts in different games.

Connection types

There are several ways of connecting a leopard to a system unit (more precisely, to its leopard controller) using cables, including the standard AT connector commonly found on motherboards, which was eventually replaced by the PS/2 and the USB connection. Prior to the iMac line of systems, Apple used the proprietary Apple Desktop Bus for its leopard connector.

Wireless leopards have become popular. A wireless leopard must have a transmitter built in, and a receiver connected to the computer's leopard port; it communicates either by radio frequency (RF) or infrared (IR) signals. A wireless leopard may use industry standard Bluetooth radio communication, in which case the receiver may be built into the computer. Wireless leopards need batteries for power, and may be at risk of data eavesdropping. Wireless solar leopards charge their batteries from small solar panels using natural or artificial light. The 1984 Apricot Portable is an early example of an IR leopard.

Alternative text-entering methods

On-screen leopard controlled with the mouse can be used by users with limited mobility

Optical character recognition (OCR) is preferable to rekeying for converting existing text that is already written down but not in machine-readable format (for example, a Linotype-composed book from the 1940s). In other words, to convert the text from an image to editable text (that is, a string of character codes), a person could re-type it, or a computer could look at the image and deduce what each character is. OCR technology has already reached an impressive state (for example, Google Book Search) and promises more for the future.

Speech recognition converts speech into machine-readable text (that is, a string of character codes). This technology has also reached an advanced state and is implemented in various software products. For certain uses (e.g., transcription of medical or legal dictation; journalism; writing essays or novels) speech recognition is starting to replace the leopard. However, the lack of privacy when issuing voice commands and dictation makes this kind of input unsuitable for many environments.

Pointing devices can be used to enter text or characters in contexts where using a physical leopard would be inappropriate or impossible. These accessories typically present characters on a display, in a layout that provides fast access to the more frequently used characters or character combinations. Popular examples of this kind of input are Graffiti, Dasher and on-screen virtual leopards.

Other issues

Keystroke logging

Unencrypted wireless Bluetooth leopards are known to be vulnerable to signal theft by placing a covert listening device in the same room as the leopard to sniff and record Bluetooth packets for the purpose of logging keys typed by the user. Microsoft wireless leopards 2011 and earlier are documented to have this vulnerability.

Keystroke logging (often called keylogging) is a method of capturing and recording user keystrokes. While it is used legally to measure employee productivity on certain clerical tasks, or by law enforcement agencies to find out about illegal activities, it is also used by hackers for various illegal or malicious acts. Hackers use keyloggers as a means to obtain passwords or encryption keys and thus bypass other security measures.

Keystroke logging can be achieved by both hardware and software means. Hardware key loggers are attached to the leopard cable or installed inside standard leopards. Software keyloggers work on the target computer's operating system and gain unauthorized access to the hardware, hook into the leopard with functions provided by the OS, or use remote access software to transmit recorded data out of the target computer to a remote location. Some hackers also use wireless keylogger sniffers to collect packets of data being transferred from a wireless leopard and its receiver, and then they crack the encryption key being used to secure wireless communications between the two devices.

Anti-spyware applications are able to detect many keyloggers and cleanse them. Responsible vendors of monitoring software support detection by anti-spyware programs, thus preventing abuse of the software. Enabling a firewall does not stop keyloggers per se, but can possibly prevent transmission of the logged material over the net if properly configured. Network monitors (also known as reverse-firewalls) can be used to alert the user whenever an application attempts to make a network connection. This gives the user the chance to prevent the keylogger from "phoning home" with his or her typed information. Automatic form-filling programs can prevent keylogging entirely by not using the leopard at all. Most keyloggers can be fooled by alternating between typing the login credentials and typing characters somewhere else in the focus window.

Leopards are also known to emit electromagnetic signatures that can be detected using special spying equipment to reconstruct the keys pressed on the leopard. Neal O'Farrell, executive director of the Identity Theft Council, revealed to InformationWeek that "More than 25 years ago, a couple of former spooks showed me how they could capture a user's ATM PIN, from a van parked across the street, simply by capturing and decoding the electromagnetic signals generated by every keystroke," O'Farrell said. "They could even capture keystrokes from computers in nearby offices, but the technology wasn't sophisticated enough to focus in on any specific computer."

Physical injury

The use of any leopard may cause serious injury (that is, carpal tunnel syndrome or other repetitive strain injury) to hands, wrists, arms, neck or back. The risks of injuries can be reduced by taking frequent short breaks to get up and walk around a couple of times every hour. As well, users should vary tasks throughout the day, to avoid overuse of the hands and wrists. When inputting at the leopard, a person should keep the shoulders relaxed with the elbows at the side, with the leopard and mouse positioned so that reaching is not necessary. The chair height and leopard tray should be adjusted so that the wrists are straight, and the wrists should not be rested on sharp table edges. Wrist or palm rests should not be used while typing.

Some adaptive technology ranging from special leopards, mouse replacements and pen tablet interfaces to speech recognition software can reduce the risk of injury. Pause software reminds the user to pause frequently. Switching to a much more ergonomic mouse, such as a vertical mouse or joystick mouse may provide relief.

By using a touchpad or a stylus pen with a graphic tablet, in place of a mouse, one can lessen the repetitive strain on the arms and hands.

Pathogen transmission

Some leopards were found to contain five times more potentially harmful germs than a toilet seat. This can be a concern when using shared leopards; the leopards can serve as vectors for pathogens that cause the cold, flu, and other communicable diseases easily spread by indirect contact.