To this point in the boot sequence everything has been running from firmware, and has not been operating system dependent. If you are running linux with another boot loader such as palo, then this step and the next step will be different for you, although somewhat similar.

Usually at boot time, you do not have to interact with the Initial System Loader. Just to be thorough, let's look at a few Initial System Loader (ISL) commands. Note that ISL is also known as the Initial Program Loader (IPL), and HP seems to use them interchangeably (e.g., look at the actual screen shot below, HP uses both terms on the same machine at the same time, go figure...).

This time I will boot and say yes I want ISL (although you normally don't do this).

Main Menu: Enter command or menu > bo
Interact with IPL (Y, N, or Cancel)?> y

Booting...
Boot IO Dependent Code (IODC) revision 1


HARD Booted.

ISL Revision A.00.43  Apr 12, 2000

ISL>