C++ Primer, Fifth Edition

Using the class or struct Keyword

We also made another, more subtle, change: We used the class keyword rather than struct to open the class definition. This change is strictly stylistic; we can define a class type using either keyword. The only difference between struct and class is the default access level.

A class may define members before the first access specifier. Access to such members depends on how the class is defined. If we use the struct keyword, the members defined before the first access specifier are public; if we use class, then the members are private.

As a matter of programming style, when we define a class intending for all of its members to be public, we use struct. If we intend to have private members, then we use class.