Most profitable business in IBM is mainframe.
Q: why not yet replaced by newer technologies like java and unix?
A: actually mainframe can also run java and unix
Reason: extremely reliable. Decision-makers dare not touch them. It’s hard to recreate something so reliable. May take many years to demonstrate the reliability.
Reason: mainframe is improving too, as competing technologies improve.
Reason: Terminals (like ATM and airline booking terminals) are locked into IBM mainframe. They can’t work with newer servers. You must replace terminals along with mainframe.
Reason: mainframe processing power is still formidable.
Reason: IBM killed its mainframe competitors chiefly Hitachi. I don’t know if this prolongs or shortens mainframe shelf-life.