At Linux Expo in London this week, companies are showing off the latest additions to the open source arsenal, including tools designed to step up software development and software to make Linux more attractive for high-end servers and workstations. In the meantime, Linux has grown in the last year into a serious competitor for Microsoft's Windows operating system, according to industry experts.

Borland, the troubled software company specializing in developers' tools, is demonstrating its Kylix development environment at the show. Kylix, introduced earlier this year, is designed to make it easy to program applications for both Windows and Linux, and is the first easy-to-use RAD (Rapid Application Development) environment for Linux.

It uses Borland's Delphi programming language, which competes with Microsoft's Visual Basic on Windows. Microsoft does not make a version of Visual Basic for Linux. Using Kylix it is possible to create software in Delphi, then simply recompile it in Kylix to run on Linux.

"This is generating a lot of excitement," said Borland's RAD product line manager Jason Vines. br>

IBM will be showing off its new software to improve Linux performance for high-end computers in large businesses. Recently IBM launched version 1.0 of JFS, a project to improve the Linux file system. A file system controls the way documents are stored on a computer. IBM also released new software to improve Linux performance on multi-CPU PCs, important for the high-powered servers used by enterprises.

IBM has quickly transformed itself into Linux's most vocal advocate in the corporate world. The company has pledged to spend US$1b (about 7b pounds) this year on Linux development, and is introducing the open source operating system into many of its products.

At the same time, Linux is increasingly making its way into non-PC devices such as set-top boxes and handheld organizers. It competes in this so-called "embedded" market with Microsoft, among others, and its Windows Embedded and Windows CE operating systems, but Linux gives developers more freedom and is available more cheaply than proprietary operating systems. IBM, for example, is demonstrating a Linux-based watch at the conference.

These new developments arrive as some see Linux maturing from its early, in-your-face days to focusing on steady, sustained growth.