DefScreen resource

Defines a character string that will be output to switch the terminal from 132-column mode to 80-column mode. Within the string, the sequence  is translated to the ASCII ESC character (U+001B).

When the 3270 model is 5, and this resource and the altScreen resource are defined, c3270 will automatically send this string to change the terminal size when the host switches from the alternate (27x132) screen to the default (24x80) screen.