Pure virtual functions and tasks in system verilog !!!

Virtual function/tasks defined in the base class may or may not be overridden in the derived class and the base class can have an implementation of the virtual function/task. sometime the definition of virtual functions/task in base class may not have any clarity on what need to be implemented these virtual functions/task must be overridden in the derived class and just a declaration is need in the base class. In this scenario virtual function / task is declared as pure. Declaring virtual method pure means no implementation for the function/task is required in the base class and the derived class must override the virtual function/task.