Package Type: Class level package and unit level package;
Class 1 level package:
1.1 In the package level package, the external interface is a collection of public, publishd members,
PROTECTED, the collection of private belongs to the implementation details of the column;
1.2 For this class of derivatives, the interface is a collection of public, public, protected,
The private section is interior implementation details.
2 unit level package:
2.1 Multiple classes declared in a Unit, mutual friend class; (the friend class is completely transparent);
2.2 Variables declared in a Unit interface part of the global variable, other Unit visible;
2.3 Variables in a Unit IMplementation section are local variables of the Unit, only in this
Unit is visible;
2.4 Each unit can have a separate initialization section (inTIALIZATION) and the anti-initialization section (Finalizaion),
The initialization of the Unit level can be automatically performed with the support of the compiler.
