The description below is from the book DOS the
Easy Way by Everett Murdock Ph.D.
for information about downloading the book.
Type: Internal (2.0 and later)
CTTY (device) Purpose: Changes the standard I/O (Input/Output) device to an
The CTTY command is used only for I/O (input/output) devices such as a
It cannot be used for peripheral devices such as a printer. However, DOS
not check to make sure you have entered a valid device name. If, for
you specify a printer, DOS will attempt to read from the device,
Affects only programs that use standard DOS calls. BASIC and other
that do not access I/O devices with DOS calls will not recognize device
reset using this command.
Valid device names are:
To change to another I/O device using the AUX port, enter