History of Software software for automation of accounting and manufacturing and to support some vertical industries, such as banking and insurance. Software companies originally focused on mainframes, but by the 1970s minicomputers such as the DEC PDP-11 and then the VAx re in use. Because smaller mainframes and minicomputers were less expensive, there were more of them and more of their customers were likely to acquire software packages rather than perform expensive custom development. Relational databases such as Oracle, Ingres, and Informix were big sellers on minicomputers. In the 1970s, the new idea of closed source software companies was heavily proselytized. In 1976 the en Letter to Hobbyists" written by Microsoft's Bill Gates stated that "software is not a public good but pri- vate property." In the late 1970s, men like Gates, Larry Ellison of Oracle, John Cullinane of Cullinet, and Martin Goetz of ADR were arguing for the importance of a strong software industry with closed code products, sepa- rate from the hardware industry. Cullinet and ADR were later acquired by Computer Associates. It is not a coincidence that Microsoft, Oracle, and Computer Associates were able to build on this early start to become and rernain the largest companies in the software business. 3 UNIX