The venerable VMS operating system from Digital Equipment Corp. turned 30 years old last week. Hardly anyone noticed.

Nevertheless, in an industry where change is a constant, VMS has few peers in its age bracket. The hoary software of the IBM mainframe also is over 30 years old, but that's mainly because it's embedded in a kind of castle that won't fall.

VMS never had a castle. It succeeded at first as the prime operating system of the DEC Vax minicomputer. As Data General, Wang, IBM, and others moved into minis, DEC stayed ahead with its Vax architecture powered by the VMS. VMS could run a Vax efficiently; for that matter, it could run whole clumps of Vaxes, known as Vaxclusters.

But the Vax was no castle. When competition intensified, VMS had to move on. It powered the Alpha line of servers brought out first by DEC, then Compaq Computer. When Compaq was bought by Hewlett Packard, VMS -- now known as OpenVMS -- moved on again, this time to Intel Itanium architecture servers. VMS was never royalty in a castle; it was more like a resourceful, gypsy worker.

VMS was designed by Dave "eat your own dog food" Cutler when he was one of the top programmers at DEC. Cutler would move on also, putting his development talents to work at Microsoft, where his experience led to leadership of the Windows NT project. NT's security gains over earlier forms of Windows flowed directly out of his VMS experience.

VMS was designed to be secure from the ground up, not as an afterthought, and it had multiple barriers for would-be intruders. It would check the role of someone giving it commands to see whether they were authorized to do what they were trying to do. If your password was X, and an intruder starting trying to guess passwords using L, M, N, etc., by the time he got to X, VMS would have spotted the pattern and locked his account, even when he got to the right letter.

"We've never had a virus on OpenVMS. It's never been hacked into for the life of the product," says Ann McQuaid, general manager of OpenVMS at HP.

Gareth Williams, associate director of the Smithsonian Astrophysical Observatory Minor Planet Center, knows about VMS' security and other virtues. Williams is a self-taught programmer trained in astronomy. When he arrived at the observatory on the Harvard campus in Cambridge, Mass., it became his job to track the 400,000 orbits of known asteroids and comets in the solar system. His computing resources for the job were two MicroVaxes running VMS. The system was gradually expanded with several larger Vaxes until the center had a cluster of 12.

The center shares space with the university's observatory, and when the pinch was put on office space, it was decided by building authorities that 12 Vaxes in an office were a waste of white collar space. Seven were wheeled off to a remote corner of the building known as the "gobs of gear" room, says Williams. But the Vaxcluster still performs, he says.

Not to worry, adds McQuaid. The Vaxcluster can run whether the computers are right next to each other or separated by up to 500 miles.

The Deutsche Borse stock exchange in Frankfurt runs on VMS. The Australian Stock Exchange runs on it. The Amsterdam police department in the Netherlands runs on it. The train system in Ireland, Irish Rail, runs on it. And Amazon uses OpenVMS as the OS for the system which controls the shipment of 112,000 customer packages of books, CDs, and DVDs every day.

The operating system "has a very loyal installed base of customers," McQuaid says, and they show no signs of wanting to give it up.

After 30 years, can this operating system go on forever? When Compaq decided to kill off the Alpha chip, "that did not sit too well around here," says Williams, who's still tracking asteroids on his Alpha servers. HP says it's willing to continue to support OpenVMS as part of its Itanium server lines. Williams can't be sure when he'll be able to migrate to Itanium or whether HP's commitment is concrete enough to warrant the conversion.

So he's stuck with an old dilemma. "We always said we would move away from VMS when something better came along. There isn't anything better," he says.