- static variable 自动 initialize to NULL(0)
- static variable can pointer to a constant or variable. When pointing to a variable, that variable must be static. Same rule applies to that variable.
- when return a value to a static variable from a function or method, the return value should be assigned to a static variable in that function.
- VC++ won't tell you your static variable contains rubbish, when it points to a non-static variable.