Is it possible to achieve encapsulation/abstraction in C?

[Vishwajith-K]

Yes. But may not be achievable in single file. If an identifier is used, it must first be declared/defined earlier. That's not the case with typedef. A type can be aliased to another type even if the first type (that is being aliased) doesn't exist earlier. Compilation succeeds, except some kind of clarification may be needed to run the code. This usage yields opaqueness for a given type. And limits user to use the provided abstraction layer (typically getter, setter) and not the underlying data.