HTTP and Sessions

Imagine a KDE application, Kedit for example. (KDE is a windows manager for Linux and compatible X systems.) A typical operation might include opening a file, modifying its contents, and saving it under another name. Kedit knows what you're doing in every step of this process. It knows that you're editing the file, where the cursor is, where you move the mouse, and so on. Even if you open a second instance of Kedit, it won't get confused; selecting Save in instance 1 won't save the file from instance 2. This is possible because Kedit (or the operating system, to be exact) knows how to associate your actions with a specific instance of the application—it receives an event like "In the instance with the PID 4711 (a PID is a ...

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