Display hack
Explanation. The program starts at GO and attempts to use the .IOTLSR system call to enable the job to use I/O instructions. Running under ITS, this succeeds and goes on to the CONO instruction which resets the display.
Out of timesharing, there is no operating system UUO handler for the .IOTLSR call, so the program will jump to the UUO handler at location 41 which just jumps back to the main program.
Display hack
A good way to start a display hack. It will run both on ITS and out of timesharing equally well.
Happy birthmonth, ITS!
According to Project MAC Progress Report IV, ITS first become operational July 1967.
