Do I need to use classes in C++?

No, you should not put everything into classes . Whoever told you that was wrong. C++ is not (just) an OO language, it is a multi-paradigm language. Additionally, putting everything into classes does not mean that code is object oriented (especially since for static methods you don’t need actual objects, just types).

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What is the use of classes?

The class is a blueprint that defines a nature of a future object. An instance is a specific object created from a particular class. Classes are used to create and manage new objects and support inheritance —a key ingredient in object-oriented programming and a mechanism of reusing code.

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