After you have successfully completed the exercise, please note that the interrupt INT 19h did not reboot the system. Instead, the interrupt was routed to the Virtual DOS Machine Manager (VDMM) by the General Protection Handler. The VDMM terminates the VDM when receiving the INT 19h.
If you start a DOS application program from an OS/2 command prompt, control is passed to the Virtual DOS Machine Manager which then starts the VDM. Execution of INT 19h does NOT terminate the OS/2 session. Instead, INT 19h terminates the VDM session only. Control is returned to the OS/2 session.
The INT19.EXE is a compiled BASIC program. The source code is shown in Figure "INT19.BAS Source Code."