Batch processing, multiprogramming, time sharing, multiprocessing, distributed systems and real-time systems can sound like interchangeable labels. The confusion shows up when an MCQ asks for the one defining difference: what a batch system queues, what multiprogramming keeps resident in memory, what time sharing guarantees the person at a terminal, and what a real-time system promises about the worst case rather than the average. Answer each of the 12 questions below before you read its explanation. For the same ground taught in lecture form, work through GATE Guidance by Sanchit Sir.
1. How to use these OS evolution MCQs
Use three passes. First, answer from memory. Second, justify in one sentence why every distractor is wrong. Third, commit to an option before you read the explanation, then name the single property that makes it correct: not the era, not the vendor, but the behaviour the definition turns on.
Keep four definitions beside you. Batch systems queue non-interactive jobs. Multiprogramming keeps several programs in memory so the CPU can run another when one waits for I/O. Time sharing adds rapid switching for interactive users. A real-time system promises a bounded, predictable response, not merely a fast average response.
2. From batch processing to multiprogramming and spooling
Early operating systems evolved to use resources better. Batch processing grouped jobs, spooling overlapped peripheral work with computation, and multiprogramming supplied ready work when a program blocked.
Q1. Batch-processing example
Which of the following is an example of a batch processing operating system?
A.
MS-DOSB.
Windows XPC.
IBM OS/360D.
macOS
Answer: C, IBM OS/360. This is the canonical batch-processing example. MS-DOS is a single-user, single-tasking personal-computer OS. Windows XP and macOS are interactive general-purpose systems. Age alone is not the test.
Q2. Identify a spooled device
Which of the following is an example of a spooled device?
A.
The terminal used to enter the input data for the C program being executedB.
An output device used to print the output of a number of jobsC.
The secondary memory device in a virtual storage systemD.
The swapping area on a disk used by the swapper
Answer: B. A printer is the classic example. Several jobs can wait in a disk-backed queue and reach the slow printer one at a time. A terminal is interactive. Virtual storage and swap areas address memory management, not peripheral queuing.
Q3. What is sufficient to characterize multiprogramming?
Which combination of the following features will suffice to characterize an OS as a multiprogrammed OS? (a) More than one program may be loaded into main memory at the same time for execution. (b) If a program waits for an event such as I/O, another program is scheduled for execution. (c) If a program terminates, another program is scheduled for execution.
A.
a onlyB.
a and bC.
a and cD.
a, b and c
Answer: B, a and b. Several resident programs provide ready work, and switching when one program waits for I/O improves CPU utilisation. Statement (c) is not distinctive. Even a simple batch monitor can start another job after the current one terminates.
Q4. Match each technique to its advantage
Match the following for operating system techniques with the most appropriate advantage:
List-I | List-II |
|---|---|
(a) Spooling | (i) Allows several jobs to improve CPU utilization |
(b) Multiprogramming | (ii) Access to shared resources among geographically dispersed computers in a transparent way |
(c) Time sharing | (iii) Overlapping I/O and computations |
(d) Distributed computing | (iv) Allows many users to share a computer simultaneously by switching processor frequently |
Codes:
A.
(a)-(iii), (b)-(i), (c)-(ii), (d)-(iv)B.
(a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)C.
(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)D.
(a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)
Answer: B. Spooling overlaps I/O and computation, so (a) matches (iii). Multiprogramming uses several resident jobs to improve CPU utilisation, so (b) matches (i). Time sharing switches the processor frequently among interactive users, so (c) matches (iv). Distributed computing gives transparent access to resources on geographically separated machines, so (d) matches (ii).
3. Time sharing, real-time systems and embedded constraints
Use a simple decision rule. Interactive fairness points to time sharing. Deterministic deadlines point to an RTOS. A dedicated function under tight resource limits points to an embedded system. Speed alone does not prove real-time behaviour.
Q5. Time-sharing example
Which of the following is an example of a time-sharing operating system?
A.
MS-DOSB.
Windows 10C.
macOSD.
UNIX
Answer: D, UNIX. Users at separate terminals receive short CPU time slices and each gets an interactive experience. MS-DOS is the single-tasking distractor. Multiple user accounts alone do not make a desktop OS a classical time-sharing system.
Q6. Real-time operating-system example
Which of the following is an example of a real-time operating system?
A.
Windows 10B.
UNIXC.
QNXD.
Linux
Answer: C, QNX. The deciding property is deterministic response within a deadline. The unqualified Windows 10, UNIX and Linux choices are general-purpose systems. Specialised real-time variants exist, but that does not change the intended classification.
Q7. Embedded-system characteristic
Which of the following is not a characteristic of an embedded system?
A.
Reactive and real timeB.
Multi-functionedC.
Single-functionedD.
Tightly constrained
Answer: B, Multi-functioned. Embedded systems are normally purpose-built, reactive and constrained in memory, power, cost or processing capacity. That differs from a general-purpose computer designed to run many unrelated applications.
4. OS families and UNIX history
These four turn on a single fact each: how strictly an operating system layers its services, what language it was written in, where it was built, and how many users it was meant to serve at once. Read what each option claims about that one fact. A familiar product name is not an argument.
Q8. OS/2 versus MS-DOS
Which of the following statements about the OS/2 operating system is correct?
A.
It is a single-tasking operating system.B.
It was implemented to be more layered than MS-DOS.C.
It allows direct user access to hardware.D.
MS-DOS is a descendant of OS/2.
Answer: B. OS/2 was designed as a more layered, multitasking system than MS-DOS. Option A wrongly calls it single-tasking. Option D reverses the ancestry.
Q9. UNIX implementation language
Almost the entire code of UNIX operating system is written in _________ programming language.
A.
CB.
PascalC.
C++D.
Fortran
Answer: A, C. Moving most of UNIX away from machine-specific assembly made the system much easier to port to different hardware. The wording says almost the entire code, not literally every line.
Q10. UNIX development location
Unix was developed at _________.
A.
Sun MicrosystemsB.
IntelC.
AT&T Bell LabsD.
Microsoft Corporation
Answer: C, AT&T Bell Labs. This tests the original development-site association. Unix came out of AT&T Bell Labs, so none of the other three companies is the development site.
Q11. Match systems and programs to their category
Match List-I with List-II:
List-I (Operating system) | List-II (Task) |
|---|---|
A. UNIX | I. Assist users in system maintenance task |
B. MS-DOS | II. Mobile device |
C. Android OS | III. Single user operating system |
D. Utility programs | IV. Multi user operating system |
Choose the correct answer from the options given below:
A.
A-III, B-IV, C-I, D-IIB.
A-I, B-II, C-IV, D-IIIC.
A-IV, B-III, C-II, D-ID.
A-III, B-I, C-II, D-IV
Answer: C, A-IV, B-III, C-II, D-I. UNIX is multi-user. MS-DOS is single-user. Android targets mobile devices. Utility programs assist with maintenance tasks and are not themselves operating systems.
5. Worked numerical: no requests in a time interval
This calculation needs a rate, a matching time unit, and the zero-event formula. Do not jump straight from the hourly rate to an exponent.
Q12. Multiuser request probability
In a multiuser operating system, 20 requests are made to use a particular resource per hour, on an average. The probability that no request is made in 45 minutes is:
A.
e⁻¹⁵B.
e⁻⁵C.
1 − e⁻⁵D.
1 − e⁻¹⁰
Answer: A, e⁻¹⁵. Treat arrivals as a Poisson process with rate 20 requests per hour.
Convert the interval:
45/60 = 0.75 hour.Find its expected request count:
λt = 20 × 0.75 = 15.Apply the zero-arrival formula:
P(N = 0) = e⁻¹⁵ × 15⁰ / 0!.Since
15⁰ = 1and0! = 1,P(N = 0) = e⁻¹⁵.
An independent unit check gives the same mean: (20/60) × 45 = 15. The e⁻⁵ choice treats 45 minutes as one quarter of an hour. The two 1 − e⁻ˣ choices use complements and the wrong interval means.
6. The traps these questions are designed to catch
Confusing pair | Decision test |
|---|---|
Queued jobs vs multiple resident jobs | Batch processing queues jobs; multiprogramming keeps multiple programs in memory. |
Apparent concurrency vs true parallelism | Rapid switching can create concurrency; multiple CPUs are needed for true simultaneous CPU execution. |
Quick average response vs guaranteed deadline | A small average is fast; a bounded predictable response is real-time. |
Multiple accounts vs classical time sharing | Accounts identify users; time sharing gives interactive users frequent CPU slices. |
For the numerical, keep the whole chain in one line: 20 requests/hour × 0.75 hour = 15, so zero arrivals has probability e⁻¹⁵. For related drills, continue with operating systems process management states MCQs and operating systems threads and process creation MCQs.
7. Short version and next practice step
Batch queues jobs. Spooling overlaps peripheral work with computation. Multiprogramming overlaps CPU work with I/O waits. Time sharing adds interactive CPU slices. Real-time systems optimise for deadline guarantees. Embedded systems are purpose-built and constrained.
Now redo all 12 without looking at the options, then explain every wrong option aloud. Use the GATE Test Series for timed practice, or browse the GATE category for a broader next topic. The goal is not to remember twelve letters. It is to recognise the defining property that makes each answer correct.
