Question

Could anybody please tell me what is the main difference
between C & C++ structures.

Answer 1

In C++ struct and class are the exact same thing, except for that struct defaults to public visibility and class defaults to private visiblity.

In C, struct names are in their own namespace, so if you have struct Foo {};, you need to write struct Foo foo; to create a variable of that type, while in C++ you can write just Foo foo;, albeit the C style is also permitted. C programmers usually use typedef struct {} Foo; to allow the C++ syntax for variable definitions.

The C programming language also does not support visibility restrictions, member functions or inheritance.