What keyword is used to create a user-defined type in C++?

In C++, both the "struct" and "class" keywords are used to create user-defined types, making the choice that includes both the correct one.

"Struct" is used to define a structure, which is a composite data type that groups together variables (often of different types) under a single name. Each variable in a structure is called a member, and members can be accessed using the dot operator. By default, members of a struct are public.

On the other hand, "class" is used to define a class, which is a more advanced concept that not only groups variables but also encapsulates functions (methods) that operate on those variables. Classes bring in the principles of object-oriented programming, allowing for the concepts of inheritance, encapsulation, and polymorphism. By default, members of a class are private.

Thus, both keywords give programmers the ability to define complex data types that suit their needs, enabling them to model real-world entities effectively in code. This flexibility allows for greater code organization and reusability, which are essential principles in software development.