1.5.1. The Sales_item Class

The purpose of the Sales_item class is to represent the total revenue, number of copies sold, and average sales price for a book. How these data are stored or computed is not our concern. To use a class, we need not care about how it is implemented. Instead, what we need to know is what operations objects of that type can perform.

Every class defines a type. The type name is the same as the name of the class. Hence, our Sales_item class defines a type named Sales_item. As with the built-in types, we can define a variable of a class type. When we write

Sales_item item;

we are saying that item is an object of type Sales_item. We often contract the phrase “an object of type Sales_item” to “a Sales_item object” or even ...

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