 Ultimately, over six million terminals in the VT series were sold, based largely on the success of the VT100s.DEC's first successful video terminal was the VT50, introduced in 1974 and quickly replaced by the VT52 in 1975.The VT52 featured a text display with 80 columns and 24 rows, bidirectional scrolling, and a custom control language that allowed the cursor to be moved about the screen.