What is the difference between C and Objective-C?

Answer 1

Object C is basically C with the "Object oriented" layer added on top. It's a superset of C that has some extra features, So everything in C is also valid in Objective C.

Answer 2

Objective-C is a strict superset of C, so everything that is valid C is also valid Objective-C. Objective-C just adds a thin object-oriented layer on top of C.

C++: it is based on C, and also adds some object-oriented extensions to C, although it's not a strict superset of C. 

C is cross-platform and is the language for native development, hands in hands with C++,from desktop computers through mobile devices to microcontroller.