C is very much in the picture. In the right hands, its still very elegant as a low level language and can be very efficient with a small footprint. It is still alive at microprocessor or embedded system level and it is the grand-daddy of many modern day languages that derive from its syntax and structure(e.g. php,Java,C++, C#....) - http://en.wikipedia.org/wiki/Category:C_programming_language_family
- For Android, C can be used for native development (http://developer.android.com/tools/sdk/ndk/index.html
). Learning C++ would also be a plus(no pun intended).
- For Apple, there's a C-derived language called ObjectiveC that implements OO concepts in a Smalltalk flavour.
Knowing C is a definite plus in not only appreciating an imperative language and reducing the learning curve for C-like derivatives, but also gives good insight into the system-level interaction with hardware.