Basic CS-Operating System [TCS Placement]: Sample Questions 5 - 5 of 35
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Question 5
Explanation
- It is a useful, memory-saving technique for multiprogrammed timesharing systems.
- A Reentrant Procedure is one in which multiple users can share a single copy of a program during the same period.
- Reentrancy has key aspects: The program code cannot modify itself, and the local data for each user process must be stored separately.
- Permanent part is the code, and the temporary part is the pointer back to the calling program and local variables used by that program.
- Each execution instance is called activation. It executes the code in the permanent part, but has its own copy of local variables/parameters.
- The temporary part associated with each activation is the activation record.
- Generally, the activation record is kept on the stack.
- Dynamic stack variables provide inherent reentrancy.
- Each task has ints own task.
- E. g. linked list in lstLib
- Note: A reentrant procedure can be interrupted and called by an interrupting program, and still execute correctly on returning to the procedure.