I hate apps that don't allow you to copy text from a comment field. It gives you a taste of the world without Larry Tesler and Tim Mott, and it's not a magnificent one

[Note: Tesler worked at Xerox PARC, Apple, Amazon, and Yahoo!. While at PARC, Tesler's work included Smalltalk, the first dynamic object-oriented programming language, and Gypsy, the first word processor with a graphical user interface (GUI) for the Xerox Alto. During this, along with colleague Tim Mott, Tesler developed the idea of copy and paste functionality and the idea of modeless software. ]

This article explains the role of the X Window System when it was first developed in the 1980s, and today. I highlight three advanced traits:

X was highly portable, so that applications written for X could run on virtually any Unix system, on BSD, on GNU/Linux, and on the Mac.
X allowed distributed computing. You could run graphical applications hosted on another computer, displaying them on your local desktop.
X was customizable to an almost limitless extent. This made X a platform for sophisticated interfaces such as KDE and GNOME.