What is key/topic of Structural language and OOP language??

Question

what are the basic topic or idea of structural language such as c and object oriented language such c++, java etc?

Answer 1

The basic idea of OOP is that you can create Classes and Objects.
A class is the code that defines how an object behaves.
The object is the incarnation of the class at runtime (when the program is running).
The reason this is useful is because you can define a class that does a task in a few lines of code and it will reuse the code over and over again.
Whereas in other languages you would have to rewrite the code everytime the task needs doing.
Which is bad because it makes the program longer than it needs to be and can cause problems.