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Application Interface
by Tam

With the help of some software tools organize the output graphical user interface? You can, of course, 'sew' support for all currently existing video card, but it's a lot of work, plus what if the card was issued after the release of software product? Issue updates? This is also a lot of work for programmers company, which produces our text editor? It is obvious that this is a dead end road. ibm architects found a more elegant solution: api – Application Programm Interface (software Application Interface). Briefly the essence of the idea is this: thought out a standard 'language' in which all applications must communicate a command unit, returning to the example with the graphics card, comes up with a set of methods drawing, causing that your application can draw on the screen some primitives: point, line, rectangle, text. Of these methods, developers of the operating system are whole libraries and distribute free to all of the key at this point, programming languages. It turns out the programmer who is working on a text editor to draw a line to the screen, do not necessarily care about the support of all well-known video, but simply to write code like: Add ('biblioteka_videoprotsedur'); (0,0,100,100); Thus custom applications have learned to communicate with the operating system on standard language, but it did not solve the problem of multiple devices having different capabilities. As the operating system know how to file, click it to this device? It was then, and came up with the driver.

The idea is: let the operating system provides a special program signals on a standard for this operating system, language, and already this program will give commands to the device. This program, the driver is written for each device separately, so she knows how to communicate with him, is written and distributed by the driver, who developed the device. The word driver can be translated as 'upravlyatel' in this context so called program designed to interoperability of the operating system and device. The path that the signal passes from the moment of 'desire' application to draw a primitive, until the appearance of his on-screen, can be symbolically picture: 1. Application calls the API-method of the operating system. 2.

Operating system to the driver card and a standard language gives instructions for drawing primitives. 3. Video card driver, using low-level, unique to this model, graphics, language, gives it (video card) instructions for drawing primitives. 4. The video card converts the digital signal from the driver into an electric current that is passed to the monitor. 5. Monitor and interpret the signal that came to him, draws a picture. At first glance, unduly complex, but the use of such a model has many advantages, some of which I have described above. I hope after reading this article, the reader, it became clear that such a driver, and why it arose.



February 3rd


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