Disclaimer: there is to tell, is not defined in the storage time can fool the compiler, but must find links to all defined subroutines time,
Definition: given the physical storage space
Initialization: storage space to put the initial value
Use: With space to put value
Note: you can use pre-defined, no statement, statement of purpose is to help find storage space; constant different from ordinary variables, the class inside after the completion of open space, must be initialized before use,
Range: capable of being deployed, to
Life cycle: only generate local storage space called the definition, only the beginning of life, the general definition at the beginning, as a member variable objects exist only when defined objects.
To define, in a statement prior to use, look long to live
Defined variables int a; declare variables extern a;
Defined only once, declaring class only once. Other statements multiple times
