Explain the Thread Contextual Data 

Threads in Net Ware carry additional context as well. Per-thread, stacks, errno, Net Ware Errno, t_errno and others are available to the application developer. In addition, Net-Ware provides a two fold  mechanism for application per-thread data management. First, Net Ware provides a  set  of calls, Save ThreadDataAreaPtr() and GetThreadDataAreaPtr, to manage per-thread contextual data. Theae functions are used to store and retrieve, respectively, per-thread user data  and may be called anywhere in an application program.

In addition, the thread contextual data managed via the above functions can be accessed through use of the get_thread_data_area_ptr( ) macro defined in library.h. This macro is used to access the thread contextual data and can be  called as an  LVALUE  to an  equation. This macro can be altered to allow a programmer to user the function as a 4-byte entity in any equation or instruction.