Yes, everything useful is C or some variation of it.

Java is based off of C.

C++ is based off of C.

Javascript is based off of C.

PHP is based off of C.

If you want to do web development server side you can use C... or java, or php.

If you want to do webclient side development you can use javascript.

If you want to do desktop applications you can learn C/C++/Java.