The xterm program is a terminal emulator for the X Window System. It provides DEC VT102 and Tektronix 4014 compatible terminals for programs that can't use the window system directly.
This version implements ISO/ANSI colors using the "new" color model (i.e., background color erase). It also implements most of the control sequences for VT220. See the xterm FAQ
I decided to work on this in early 1995, to support ded and add (and incidentally ncurses) in the X environment. Several people had made modifications to xterm to support color, but none (except for the completely independent rxvt) implemented background color erase. That is rather like preferring MS-DOS to UNIX. Completely mystifying.
Being bogged down in ncurses, I didn't get involved in xterm until the very end of 1995, after working on atac.
I implemented a workable version of colorized xterm just at the point where XFree86 3.1.2B was announced, complete with a color xterm. As luck would have it, they'd incorporated the "old" color model. So I joined the XFree86 project to fix it.
As I learned more about xterm, I realized that it implemented part of VT220 (i.e., the locking shifts for extended character sets). Since a number of people on the Internet are looking for a good VT220 emulator, it seemed a natural follow-on project to make xterm a good VT220 emulator. By the release of XFree86 3.2, I had implemented most of the control sequences, except for a handful (DECSTR, the KAM and SRM modes, the ones pertaining to doublesize and soft characters, and of course, blink).
See the CHANGE LOG for details.
To support this, I also am working on vttest.
luit, which is used to allow xterm to support character encodings other than ISO-8859-1 and UTF-8.
There are numerous references on the net to xterm. Here are a few of the more interesting ones: