Hi willisx The operating system that shipped with the Ibook depends on what year it is. They can run operating systems from 10.0 all the way to 10.4.11. And they can run os 9 in classic  Some can run 10.5 for ppc also. 10.5 has no classic mode in it though.

If you know the specific model identifier then you can find all info at   www.everymac.com

You can also look  a Mac up by the serial number  www.everymac.com/ultimate-mac-lookup/

You can check the specs of ALL iBook models (G3 + G4) at everymac.com

http://www.everymac.com/systems/apple/ibook/index-ibook.html

If your iBook has a processor less than 867MHz it won't be able to run

Mac OS X 10.5 Leopard, though methods exist to allow it unofficially.

Old first model colors iBook G3 (not white dualUSB) have other limits.

A reference app for Apple product specifications, download http://mactracker.ca

Hopefully you can match your questions with the various databases online.

Good luck & happy computing!

you can boot your ibook g3 with os 8.6 to os 9.2 or osx 10 to 10.4, max update 10.4.11, it depends on the model you own

ibook g4 just osx from 10.3 to 10.5, max update 10.5.8

if you plan to buy a used ibook i suggest to get an ibook A1133 1,33 ghz with at least 1 gb ram, it boots from 10.4.6 retail dvd (not just 10.4) using integrated optical drive or 10.5 using external usb dvd dl drive, in 10.5.8 the machine runs pretty well and you can do almost all common operations