- LPU MCA Semester 1
- CAP366
- Unit 1
CAP366 · Unit 1: Introduction to operating systems
Types of operating systems
11 practice questions · in the MTE and ETE syllabus
Key points
- Batch: no interaction, grouped jobs
- Time-sharing = multiprogramming + frequent switching
- Hard real-time: deadline miss is failure
- SMP: peers; asymmetric: master and slaves
Operating systems are classified by how they run jobs.
| Type | Idea | Example |
|---|---|---|
| Batch | Similar jobs grouped, no interaction | Overnight payroll |
| Multiprogrammed | Several jobs in memory so CPU never idles | Disk wait covered by another job |
| Time-sharing | Multiprogramming plus rapid switching for interactive users | Multi-user UNIX |
| Hard real-time | Missing a deadline is a failure | Air-bag controller |
| Soft real-time | Occasional misses tolerated | Video playback |
| Distributed | Separate machines cooperating over a network | Cluster |
| Multiprocessor | Several CPUs sharing memory under one OS | Server with SMP |
In symmetric multiprocessing (SMP) every processor performs all tasks; in asymmetric a master assigns work to slaves.
Exam pitfall: multiprogramming is about CPU utilisation (works on one CPU), while time-sharing adds interactive response. Do not mix up hard and soft real-time: the question is whether a missed deadline is catastrophic.
Try two questions
A factory robot controller must process each sensor reading within 5 ms every time, or the part is destroyed. Which type of OS suits it?
- Time-sharing operating system
- Hard real-time operating system
- Batch operating system
- Network operating system
Show the answer
B. A missed deadline means failure, which defines a hard real-time system. Time-sharing and batch systems offer no such guarantee.
Why not A: Time-sharing aims for fair, interactive response and gives no guaranteed deadline.
Why not C: Batch systems run queued jobs without interaction and with no timing guarantee.
Why not D: A network OS provides file and printer sharing across machines, not deadline guarantees.
Which comparison of multiprogramming and time-sharing is correct?
- Multiprogramming needs a timer interrupt for every switch, while time-sharing switches only on I/O waits
- Time-sharing runs one job to completion before it admits another, unlike multiprogramming
- Multiprogramming keeps a single job in memory, while time-sharing keeps several jobs loaded
- Multiprogramming switches jobs when one waits for I/O, while time-sharing also switches on a timer for quick response
Show the answer
D. Multiprogramming raises CPU utilisation by running another job during I/O. Time-sharing adds timer-driven switching for interactive users.
Why not A: The roles are reversed; the timer is what time-sharing adds.
Why not B: Running to completion describes simple batch execution, not time-sharing.
Why not C: Multiprogramming itself means keeping several jobs in memory at once.