1. Input device is any peripheral (piece of computer hardware equipment) used to provide data and control signals to an information processing system such as a computer or otherinformation appliance. Input and output devices make up the hardware interface between a computer and a scanner or 6DOF controller.
Whatever goes into the computer. Input can take a variety of forms, fromcommands you enter from the keyboard to data from another computer ordevice. A device that feeds data into a computer, such as a keyboard ormouse, is called an input device.
Many input devices can be classified according to:
§ modality of input (e.g. mechanical motion, audio, visual, etc.)
§ the input is discrete (e.g. key presses) or continuous (e.g. a mouse's position, though digitized into a discrete quantity, is fast enough to be considered continuous)
§ the number of degrees of freedom involved (e.g. two-dimensional traditional mice, or three-dimensional navigators designed for CAD applications)
Pointing devices, which are input devices used to specify a position in space, can further be classified according to:
§ Whether the input is direct or indirect. With direct input, the input space coincides with the display space, i.e. pointing is done in the space where visual feedback or the cursor appears.Touchscreens and light pens involve direct input. Examples involving indirect input include the mouse and trackball.
§ Whether the positional information is absolute (e.g. on a touch screen) or relative (e.g. with a mouse that can be lifted and repositioned)
Direct input is almost necessarily absolute, but indirect input may be either absolute or relative. For example, digitizing graphics tablets that do not have an embedded screen involve indirect input and sense absolute positions and are often run in an absolute input mode, but they may also be set up to simulate a relative input mode where the stylus or puck can be lifted and repositioned
Computer program (also a software program, or just a program) is a sequence of instructions written to perform a specified task for a computer.[1] A computer requires programs to function, typically executing the program's instructions in a central processor.[2] The program has an executable form that the computer can use directly to execute the instructions. The same program in its human-readable source code form, from which executable programs are derived (e.g., compiled), enables a programmer to study and develop its algorithms.
Computer source code is often written by computer programmers. Source code is written in a programming language that usually follows one of two main paradigms: imperative or declarativeprogramming. Source code may be converted into an executable file (sometimes called an executable program or a binary) by a compiler and later executed by a central processing unit. Alternatively, computer programs may be executed with the aid of an interpreter, or may be embedded directly into hardware.
Computer programs may be categorized along functional lines: system software and application software. Two or more computer programs may run simultaneously on one computer, a process known as multitasking.
Command is a directive to a computer program acting as an interpreter of some kind, in order to perform a specific task. Most commonly a command is a directive to some kind ofcommand line interface, such as a shell.
Specifically, the term command is used in imperative computer languages. These languages are called this, because statements in these languages are usually written in a manner similar to theimperative mood used in many natural languages. If one views a statement in an imperative language as being like a sentence in a natural language, then a command is generally like a verb in such a language.
Many programs allow specially formatted arguments, known as flags, which modify the default behaviour of the command, while further arguments describe what the command acts on. Comparing to a natural language: the flags are adverbs, whilst the other arguments are objects.
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