A task control block is implemented to provide more efficient user task access
to task-specific variables and context information. The task control block uses
multiple portions located in both protected system space and unprotected "user"
space. Task-specific variables may be located in the user task control block, allowing
user tasks to directly access these variables (without a system call). Sensitive
task-specific state information may be located in the system task control block,
preventing direct access by user tasks. The amount of time needed to perform context
switching is reduced, and the execution time for user tasks may be reduced as well.
