Java is losing popularity despite the recent release of a major upgrade to the platform, according to the latest monthly assessment of programming languages by Tiobe Software.

The October edition of the Tiobe Programming Community Index, released on October 9, found that Java lost popularity in September, with an estimated 17.91% of developers using it as opposed to 18.76% in the previous month's index. Java still finished as the top language, but if the downward trend continues, the C language, ranked second with 17.71% of users, will be number one next month, Tiobe said.

Java has been tops in the index from 2001 until now with a few exceptions between mid-2004 and mid-2005 and couple of months last year, when C took over, said Paul Jansen, managing director at Tiobe. He anticipates Java facing a long-term downward trend based on what he sees happening in the field. "This downward trend is probably caused by the fact that the Java language evolves too slowly compared to other languages, such as C#," Jansen said.

In July, Oracle released Java SE (Standard Edition 7) the first major update in more than five years. The release features accommodations for multi-core processors and dynamic languages. Java SE 8 is due in 2013, featuring the planned Nashorn JavaScript engine.

Rounding out the top 10 languages in Tiobe's index were C++, PHP, C#, Objective-C, Visual Basic, Python, Perl, and JavaScript. Objective-C and Transact-SQL scored all-time highs, with usage rates of 6.25% and 0.91% respectively, while Assembly re-entered the top 20 by claiming the 19th spot. Visual Basic.Net jumped to the 25th spot after ranking 39th last month, while F# dropped from 23rd to 46th.

Tiobe's index is based on the number of skilled engineers worldwide, course and third-party vendors, with search engines including Google, Bing, and Yahoo as well Wikipedia used to calculate ratings.