High Quality Content by WIKIPEDIA articles! 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.