Model-View-Presenter
In MVP, the Presenter contains the UI business logic for the View. All invocations from the View delegate directly to the Presenter. The Presenter is also decoupled directly from the View and talks to it through an interface. This is to allow mocking of the View in a unit test. One common attribute of MVP is that there has to be a lot of two-way dispatching. For example, when someone clicks the "Save" button, the event handler delegates to the Presenter's "OnSave" method. Once the save is completed, the Presenter will then call back the View through its interface so that the View can display that the save has completed.
MVP tends to be a very natural pattern for achieving separated presentation in WebForms. The reason is that the View is always created first by the ASP.NET runtime. You can find out more about both variants.
Two primary variations
Passive View: The View is as dumb as possible and contains almost zero logic. A Presenter is a middle man that talks to the View and the Model. The View and Model are completely shielded from one another. The Model may raise events, but the Presenter subscribes to them for updating the View. In Passive View there is no direct data binding, instead, the View exposes setter properties that the Presenter uses to set the data. All state is managed in the Presenter and not the View.
- Pro: maximum testability surface; clean separation of the View and Model
- Con: more work (for example all the setter properties) as you are doing all the data binding yourself.
Supervising Controller: The Presenter handles user gestures. The View binds to the Model directly through data binding. In this case, it's the Presenter's job to pass off the Model to the View so that it can bind to it. The Presenter will also contain logic for gestures like pressing a button, navigation, etc.
- Pro: by leveraging data binding the amount of code is reduced.
- Con: there's a less testable surface (because of data binding), and there's less encapsulation in the View since it talks directly to the Model.
Model-View-Controller
In the MVC, the Controller is responsible for determining which View to display in response to any action including when the application loads. This differs from MVP where actions route through the View to the Presenter. In MVC, every action in the View correlates with a call to a Controller along with an action. In the web, each action involves a call to a URL on the other side of which there is a Controller who responds. Once that Controller has completed its processing, it will return the correct View. The sequence continues in that manner throughout the life of the application:
Action in the View
-> Call to Controller
-> Controller Logic
-> Controller returns the View.
One other big difference about MVC is that the View does not directly bind to the Model. The view simply renders and is completely stateless. In implementations of MVC, the View usually will not have any logic in the code behind. This is contrary to MVP where it is absolutely necessary because, if the View does not delegate to the Presenter, it will never get called.
Presentation Model
One other pattern to look at is the Presentation Model pattern. In this pattern, there is no Presenter. Instead, the View binds directly to a Presentation Model. The Presentation Model is a Model crafted specifically for the View. This means this Model can expose properties that one would never put on a domain model as it would be a violation of separation-of-concerns. In this case, the Presentation Model binds to the domain model and may subscribe to events coming from that Model. The View then subscribes to events coming from the Presentation Model and updates itself accordingly. The Presentation Model can expose commands which the view uses for invoking actions. The advantage of this approach is that you can essentially remove the code-behind altogether as the PM completely encapsulates all of the behavior for the view. This pattern is a very strong candidate for use in WPF applications and is also called Model-View-ViewModel.
There is a MSDN article about the Presentation Model and a section in the Composite Application Guidance for WPF (former Prism) about Separated Presentation Patterns
In practice, the difference is in the location where the preprocessor searches for the included file.
For #include <filename>
the preprocessor searches in an implementation dependent manner, normally in search directories pre-designated by the compiler/IDE. This method is normally used to include standard library header files.
For #include "filename"
the preprocessor searches first in the same directory as the file containing the directive, and then follows the search path used for the #include <filename>
form. This method is normally used to include programmer-defined header files.
A more complete description is available in the GCC documentation on search paths.
Best Answer
In Linux the graphical user interface is not a part of the operating system. The graphical user interface found on most Linux desktops is provided by software called the X Window System, which defines a device independent way of dealing with screens, keyboards and pointer devices.
X Window defines a network protocol for communication, and any program that knows how to "speak" this protocol can use it. There is a C library called Xlib that makes it easier to use this protocol, so Xlib is kind of the native GUI API. Xlib is not the only way to access an X Window server; there is also XCB.
Toolkit libraries such as GTK+ (used by GNOME) and Qt (used by KDE), built on top of Xlib, are used because they are easier to program with. For example they give you a consistent look and feel across applications, make it easier to use drag-and-drop, provide components standard to a modern desktop environment, and so on.
How X draws on the screen internally depends on the implementation. X.org has a device independent part and a device dependent part. The former manages screen resources such as windows, while the latter communicates with the graphics card driver, usually a kernel module. The communication may happen over direct memory access or through system calls to the kernel. The driver translates the commands into a form that the hardware on the card understands.
As of 2013, a new window system called Wayland is starting to become usable, and many distributions have said they will at some point migrate to it, though there is still no clear schedule. This system is based on OpenGL/ES API, which means that in the future OpenGL will be the "native GUI API" in Linux. Work is being done to port GTK+ and QT to Wayland, so that current popular applications and desktop systems would need minimal changes. The applications that cannot be ported will be supported through an X11 server, much like OS X supports X11 apps through Xquartz. The GTK+ port is expected to be finished within a year, while Qt 5 already has complete Wayland support.
To further complicate matters, Ubuntu has announced they are developing a new system called Mir because of problems they perceive with Wayland. This window system is also based on the OpenGL/ES API.