- 2071 Bhadra · 2+8 marks
Supervisor call; batch, RT, time sharing
Short answer
A supervisor call (SVC) is a system call causing a trap to kernel mode, enabling controlled access to privileged services. Batch runs jobs sequentially with no interaction for high throughput. Interactive provides direct user dialogue with short response. Real-time guarantees bounded deadlines via preemptive scheduling. Time-sharing shares CPU among multiple users in small time quantums.
What is the role of supervisor call in an operating system? Write down the major differences between the following types of operating system: a) Batch system b) Interactive system c) Real time system d) Time sharing system.
Role of supervisor call
A supervisor call (SVC), also called a system call, is the instruction by which a user program asks the OS (supervisor) to perform a privileged service such as I/O, memory allocation or process creation. It causes a trap that switches the CPU from user mode to supervisor (kernel) mode and passes control to the OS routine, then returns to user mode. Its role is to give programs controlled access to protected operations, so that the OS can check the request and protect the system and other users.
Differences between the types
| Basis | Batch | Interactive | Real-time | Time-sharing |
|---|---|---|---|---|
| Aim | Maximise throughput / CPU use | Quick response to a user's commands | Meet deadlines | Share CPU among many users fairly |
| User interaction | None while the job runs | Direct, continuous | Mostly with sensors/devices | Many users at terminals at once |
| Job handling | Jobs grouped in batches, run in sequence | Commands processed as typed | Event/interrupt driven tasks | CPU switched in small time slices |
| Response time | Long (hours) | Short (seconds) | Guaranteed, very short and bounded | Short (about 1 s) |
| Scheduling | FCFS / SJF | Round robin / priority | Priority-based, preemptive (RM, EDF) | Round robin |
| CPU idle | Possible during I/O | Reduced | Kept ready for events | Minimal (multiprogramming) |
| Examples | Payroll, bank statements | Word processor, PC OS | Missile control, robotics, VxWorks | UNIX, Multics |
✓ Answer checked by Claude Opus 5.5 (high effort)
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