Love it or hate it, Microsoft did not capture the lion's share of the desktop software market without giving people what they wanted.

But Bill Gates's empire is now involved in its biggest battle yet over something most people think does no more than put pretty graphics on World Wide Web pages Java. For Microsoft realises Java is more than this, and may provide the biggest threat yet to the dominance of its Windows software.

Java's proponents declare it to be a whole new paradigm in computing. Computing started in the 1960s with mainframes, based on centralised computing and dumb terminals. Then IBM's personal computer came to life with Microsoft's DOS and Windows products, bringing computing power to the desktop.

The popularity of networks in the last decade led the client/ server model, but networks of independent machines also caused administration headaches. Enter Java and network computing.

Java is a computer language suited to networking. Though associated with the Web, its origins predate it. In 1990 a disgruntled 25-year-old software engineer in Sun Microsystems, Patrick Naughton, planned to resign because of the mess created by so many software standards in the company's products. However, his protest caught the attention of Sun's chief executive, Scott McNealy, who asked him to stay and formed a team to develop a new product addressing his concerns.

Over the following three years the team developed Java (originally called Oak), a simple language which could run on any platform equipped with the software needed to run it a Java Virtual Machine.

That probably would have been the end of the story if it hadn't been for another development at the same time: the Web. Netscape developed Navigator, the most popular Web browser, and decided to incorporate Java into it. Java applets (Web applications) quickly became popular for adorning Web pages, but this was only its beginning. Java applications differ from other computer languages in that they reside in a central server and download to the client only when they are run there. So, for example, if you click on a document to edit it, not only the document but the word processor also downloads to your machine, which can be any platform, such as a PC running Windows, a MAC, a UNIX workstation, or anything, once it contains a Java Virtual Machine.

This idea has opened up new possibilities, and has been seized upon by companies like Sun, IBM, Oracle and others which have been looking for years to dethrone Microsoft.

Java's backers are proud of its potential. Coupled with Network Computers (NCs) small, cheap, diskless computers which can only run networked applications Java is set to reduce the cost of computing by up to 70 per cent, according to INPUT, a Californian research firm. It will allow companies to extend the life of old, so-called "legacy" machines, and will reduce maintenance costs too. Analysts estimate the cost of running a typical PC is anything from $6,000 (£3,973) a year (Gartner Group's estimate) to $12,000 a year (Sun's estimate). Java should reduce this because most of the administration and software upgrading is needed on the server only.

Java should offer savings for software developers too, meaning cheaper software for users. Sun has a set of tests for what it calls "100 per cent Pure Java", which offers the promise of "Write once, run anywhere". Thus developers are spared the cost of writing several versions for several architectures, and since the software is only downloaded when run, they save distribution costs also.

So is it any wonder the software world is excited about Java? Everyone except Microsoft, that is, which wants Sun to hand over ownership of Java to a standards body. Sun is refusing, and Microsoft's response has been typical: beat them at their own game. It put a modified mainly improved version of Java in its recently released Internet Explorer 4.0 and other Java products, triggering legal action by Sun.

But while the giants battle over ownership of Java, the war is really about who will provide the most popular software in the coming years. If Java lives up to its developers' promises, businesses and small users look set to reap the benefits of extra choice and hardware independence.