Q: How many IBM types does it take to change a light bulb? A: Fifteen. One to do it, and fourteen to write document number GC7500439-0001, Multitasking Incandescent Source System Facility, of which 10% of the pages state only "This page intentionally left blank", and 20% of the definitions are of the form "A:..... consists of sequences of non-blank characters separated by blanks".