IPL

=IPL (Initial Program Load)=

Running the Hercules emulator program is like turning on the power switch of a computer

Unlike most P.C's however, Hercules just emulates the hardware, there is no "BIOS" / or O.S. (operating system) like Windows / Linux / OSX ... etc running, or even more appropriately, any kind of mainframe O.S. running.

Additionally, starting the Hercules program is different than turning on your p.c., because while starting / running Hercules is like turning on the "power", the actual CPU(s) (Hercules can emulate more than one cpu "core" at a time), will be in a "stopped" state.

Most p.c's never have their cpu stopped, as when they are turned on, the CPU is automatically enabled and starts running the BIOS program. The BIOS progam then loads your operating system.

Hercules (and a real 390 for that matter), differ from your p.c., in that after being powered on, they need to have the CPU started and then usually some kind of O.S. / program is loaded.

The cpu is started and the O.S. loaded by means of the Hercules IPL command.

The cpu can also be started with the Hercules restart and Hercules start commands.

The IPL command takes a device address as a parameter (the device where the O.S. is located), and then attempts to load the O.S. from that device.

More precisely, the Hercules IPL command simply emulates a particular I/O channel command, called Read IPL