There had been a growing buzz about the I.P.O. of software maker VMware. But on its first day of trading, it exceeded all expectations. At the close of business, shares were going for $51, which is $22 higher than the offering price of $29. That means the company’s initial public offering was the largest by a tech company since Google went public in 2004, and raised about $1.1 billion. VMware enjoyed a 70% rise in sales last year, and it’s estimated that the company has an 85% share of the virtual software market. Virtual software allows a computer to run several different operating systems (or several versions of the same OS). That means, in essence, more work can be done on fewer computers, reducing costs. Both Windows and Linux run on VMware’s virtual machine software. VMware’s main competitors are Microsoft and several open source startups, but VMware already has a dominant position in a field that’s set to burgeon over the next several years. However, VMware is likely to come under pressure from Microsoft, which will introduce the beta of its new virtual software offering, Veridian, this fall. Needless to say, VMware’s 3,000 employees, most of whom have shares, are jubilant, but so are the company’s investors, which include Intel and Cisco. But the big winner is computer storage and software company EMC, which bought VMware in 2003 for $635 million in cash and still owns 86% of the company. Given that VMware is now valued at about $19.5 billion, it’s not surprise that EMC’s chief financial officer, said, “It’s been a great investment.” It’s expected that VMware will begin to make acquisitions.