【systemverilog】 variable Scope and lifetime

Variables declared outside a module, program, interface, checker, task, or function are local to the
compilation unit and have a static lifetime (exist for the whole simulation).

Variables declared inside a module,interface, program, or checker, but outside a task, process, or function, are local in scope and have a static lifetime.

Variables declared inside a static task, function, or block are local in scope and default to a static lifetime.

Class methods and declared for loop variables are by default automatic,regardless of the lifetime attribute of the scope in which they are declared.

下面举个栗子：

task A();
  int a;
  B();
endtask

task B();
  a = 1; //compile error 
endtask

上述code中 a 是 task A的局部变量，所以task B无法对a进行操作。