You see "Open Firmware" text and a prompt on your PowerBook‘s screen

When you turn on your PowerBook you see a white screen with this text:
Open Firmware, X.XX
To continue booting the Mac OS type:
BYE<return>
To continue booting from the default boot device type:
BOOT<return>
ok
0)

This screen is the Open Firmware screen. Beginning with Power Macintosh computers equipped with PCI slots, Apple has used a firmware operating system called Open Firmware for controlling hardware.

Open Firmware is a cross-platform firmware standard for controlling hardware and is used by all PCI-based Mac OS computers. Open Firmware is used mainly by Apple hardware developers and rarely is there a need to start up into Open Firmware.

While it is difficult to start up into Open Firmware, it does happen if you hold down the Option-Command-O-F keys when the computer starts up after having been shut down. The PowerBook should never start up into Open Firmware on its own.

If you are at the Open Firmware screen and want to go back into Mac OS, type "BYE" without the quotes at the command prompt, then press the Return key. This exits Open Firmware and continues starting up into Mac OS.

Only PCI-based PowerBooks will start up into Open Firmware. These started with the PowerBook 2400, 3400, and G3/G3 series computers. Previous PowerBook models will not start up into Open Firmware.
Published Date: Feb 20, 2012