The VT420 was a computer terminal designed by Digital Equipment Corporation (DEC). Introduced in 1990, it fit up to 50 lines on the screen and supported two sessions, either one through each communication port, or by multiplexing two sessions on one line with a suitable terminal server. From a software point of view, it allowed the creation of windows on the screen by supporting rectangle operations and left and right margins for the first time.
All DEC terminals that came after the VT100, including the VT420, are able to emulate their ancestor, although they offer new features in addition to what the VT100 could do.
The VT340 (capable of ReGIS and Sixel graphics, but not responding to DP6429/ECMA-48 color text controls) was apparently retained in the product line alongside the VT420 until the VT525 was introduced as the color graphics terminal.
- Digital Equipment Corporation, Installing and Using the VT420 Video Terminal, June 1990, http://vt100.net/docs/vt420-uu/