1. History of Computer Usage Change in our life style 1950- 1960 -era of centralized computing -Mainframe computers -expensive -used by government -research, big database, payroll and other -centralized computing -US$ 1 million above 1960-1970-era of decentralized computing -terminal -dump terminal -minicomputers -larger.. normal fit in one room -cost US$ 100000-500000 http://www.eRealMedia.com/WP25/