I am not sure if I have got it right. Xlib is a library to interact with X server. X11 is just another name for X server.
Is X server just a single library? if so, why we can't access it directly? why we need Xlib?
Thanks in advance
What is the difference between X11 and Xlib
x11xorg
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You are asking five questions here, and might be better asking five questions ☺ But I'll jump in:
X is a server and can be compared to a "web server" in that it is a process that listens for incoming connections that speak a particular protocol (the X protocol) and it issues answers. The connections come from X clients, which may be on the local host or on a remote host accessed over a network.
X11 is a "major version" of the X protocol, which has evolved since inception. X11 is the most recent protocol and the most common. (Xorg is an implementation of an X server, X libraries and a collection of clients, all talking X11. There are other implementations: the largely defunct XFree86; commercial ones such as Hummingbird Exceed; forks such as XQuartz, which runs on Mac OS X)
A "window manager" is an X client which manages windows. It typically has the responsibility to decorate windows with bevels/borders, drop shadows, a menu bar containing buttons, etc. -- and handle the logic of window placement; support windows being dragged, resized or re-arranged, etc.
X requires input and it has a shared responsibility to manage that with the Kernel. Historically, X did a lot of hardware management itself. In modern times, on the Linux platform, X is gradually becoming "smaller" and delegating this responsibility to the Linux kernel. The advantages of this are: smaller X codebase; fewer "crossed-wires" with the kernel and X both trying to manage the same stuff. (an example of this is the Linux event interface, where events from mice etc. are interpreted and translated by the kernel and its drivers into the standard interface at
/dev/input/event*, which is consumed by the X server). Note that on other platforms (BSD, Solaris) X is still quite monolithic.There are many, many ways for processes to communicate with each other. I believe X clients can interact by way of the X protocol (for example, traditional X window managers need to know when other clients draw windows, in order to decorate them; pagers need to know when a window's size or position changes, in order to reflect that in the pager). D-Bus is a modern inter-process communication (IPC) technology developed to address the shortcomings of other methods. It is not X specific.
Comments in GNU libc sources (intl/l10nflist.c:_nl_normalize_codeset) state:
There is no standard for the codeset names.
Codeset names are normalized by that function to all-lowercase with all non-alphanumeric characters stripped i.e. "UTF-8" turns into "utf8".
The locale names inside the locale archive are using normalized codeset names.
Since there is no standard, GDM is well within its rights to use "utf8" and locales like 'ru_UA.utf8' are not invalid. "utf8" may not be preferred, but it is definitely acceptable (at least by libc standards) as it is the normalized form.
Best Answer
Actually, strictly speaking, X11 is the communication protocol between an X client application and an X server. The X server is the part of the system that communicates with the hardware and provides basic concepts, in particular the notion of a window on the screen, with potentially overlapping windows, and one window having the input focus. (The X server does not handle window decorations, menus, keyboard shortcuts, or anything else that is the job of the window manager.)
X is called X because it was (in part) a successor to the W window system, and X11 is version 11 of X. It took about 3 years to reach version 11 (from 1984 to 1987) and the core protocol has been stable since then.
X11 is also the base name of a software distribution that included libraries, client applications and server code using the X11 protocol. That software distribution is known as the X Window System (version 11), or X or X11 for short. This software distribution originally came from MIT, where X had been invented; it then had a sometimes tumultuous history, with an MIT-led consortium producing versions up to X11R6.3.
Nowadays, the de facto reference implementation of the X Window System is the one by the X.Org Foundation. This is a usable implementation, used by virtually all X11 installations today.
There are several X servers, most of them sharing a code base. Most users use the X.org
Xorgserver, which communicates with most display hardware out there. There are other servers such asXnest, which shows an X display inside an X window on another display, andXvfb, which is a virtual display that remains only in memory.Xlib (which has the shared object name
libX11) is just one of the libraries in the X Window System. It's a basic wrapper around the client side of the X11 protocol. Almost all X client use this library (many of them indirectly through higher-level libraries).