Programming languages rise and fall in popularity. This fact places pressure on managers to choose the right language when starting in on a big project. In my case, it places pressure on authors when choosing the language with which to exprese a concept in code. I have always chosen C, reasoning that C is readable and understandable by all C++, C#, and Java developers–which is about as broad a base of readers as I’m ever likely to reach. (Knuth’s discusses this difficult choice in the just-released Fascicle 1 of the Revision to Volume 1 of “The Art of Computer Programming” from Addison-Wesley, ISBN 0-201-85392-2)
An interesting website list the interest in specific languages based on counting Web searches for topics relating to the language. Results are normalized to avoid spurious one-off results. The methodology is explained in detail on the website. The results for the last few years are shown. I am surprised that C is still #1 (actually, it reclaimed the prize from Java a few months ago.) What is surprising is that C and Java lead C++ by such a wide margin. If I’d been asked to guess, I would have swapped the positions of C and C++ and/or possibly placed Java in first place.
There are two other interesting items. Despite rumors to the contrary, COBOL is still thriving. It’s in the most active class (those assigned a grade of ‘A’) and a fair bit ahead of Fortran and Pascal. Also, the conventional wisdom about the ‘P’ scripting languages (the three candidates for the letter P in the LAMP stack) appears to be correct. In descending order of interest, they are: Perl, PHP, and Python. Which I suspect is what most people would have guessed.
Anyway, use this info as a data point for your own decision making and in your choice of language skills.