nagy%43198.hepnet@LBL.ARPA (04/14/87)
This information is from the VMS V4.4 Release Notes section 2.3.10.1 on page 2-20: Previously, there was no $QIO system service that allowed an application to send a break to a terminal. A break can now be sent by setting TT$M_BREAK in the P5 parity flags argument to the IO$_SETMODE $QIO. Sending the break actually involves two $QIOs; one to turn it on and one to turn it off. (The break bit in the parity flags argument is set to turn on break and cleared to turn it off.) The application should use a timer in between the two $QIOs to ensure that the break has time to take effect. So, VMS V4.4 and later support generation of the Break from an application program.