After more than 4 years C is back at position number 1 in the TIOBE index. The scores for C have been pretty constant through the years, varying between the 15% and 20% market share for almost 10 years. So the main reason for C's number 1 position is not C's uprise, but the decline of its competitor Java. Java has a long-term downward trend. It is losing ground to other languages running on the JVM. An example of such a language is JavaFX script that is now approaching the top 20.

The TIOBE Programming Community index gives an indication of the popularity of programming languages. The index is updated once a month. The ratings are based on the number of skilled engineers world-wide, courses and third party vendors. The popular search engines Google, MSN, Yahoo!, Wikipedia and YouTube are used to calculate the ratings. Observe that the TIOBE index is not about the best programming language or the language in which most lines of code have been written.

The index can be used to check whether your programming skills are still up to date or to make a strategic decision about what programming language should be adopted when starting to build a new software system. The definition of the TIOBE index can be found here: http://www.tiobe.com/content/paperinfo/tpci/tpci_definition.htm.