In C++, a structure is the same as a class except for a few differences. The most important of them is security. A Structure is not secure and cannot hide its implementation details from the end user while a class is secure and can hide its programming and designing details. Following are the points that expound on this difference:
1) Members of a class are private by default and members of a struct are public by default.
For example program 1 fails in compilation and program 2 works fine.
2) When deriving a struct from a class/struct, default access-specifier for a base class/struct is public. And when deriving a class, default access specifier is private.
For example program 3 fails in compilation and program 4 works fine.
Related Article: Difference between C structures and C++ structures
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