X Window System

The X Window System (X11) is the standard windowing system for Unix-like operating systems since 1984. The free and open-source implementation maintained by the Foundation (part of freedesktop.org) since 2004, when it replaced the earlier XFree86 as the dominant server implementation. Despite being gradually superseded by Wayland in modern Linux distributions, the X server remains widely used and supported. Key features include: client-server architecture (the server manages display hardware, input devices, and rendering, while client applications communicate via the Protocol over Unix domain sockets or TCP), network transparency (applications can run on one machine and display on another over the network, a feature unique to this system that Wayland does not natively support), extension protocol system (extending the core protocol with features like RandR for display configuration, XInput2 for advanced input device handling, Composite for redirected drawing, GLX for OpenGL rendering, DAMAGE for efficient damage tracking, and XKB for keyboard layout management), hardware acceleration via DRI (Direct Rendering Infrastructure, allowing clients to access GPU hardware directly for 3D rendering), EXA and Glamor acceleration architectures (providing 2D acceleration via OpenGL), multi-monitor support (via RandR, supporting dynamic display configuration, hot-plugging, per-monitor resolutions and orientations), input device handling (keyboards, mice, touchscreens, tablets, and joysticks via evdev and libinput drivers), DPMS (Display Power Management Signaling), and access control via xhost and xauth.