Operating System MCQ Questions With Answers

Q1

Which statement best describes C++ compared with C?

Q2

An object in C++ is:

Q3

Which statement about a C++ reference is correct?

Q4

Which feature is valid for a pointer but not for a normal reference?

Q5

Function overloading in C++ requires functions to differ in:

Q6

Which of the following can be overloaded for a user-defined class?

Q7

A constructor in C++:

Q8

What is the correct purpose of a destructor?

Q9

Which statement about `new` is correct?

Q10

Which access level is the default inside a `class` in C++?

Q11

What is the main purpose of a namespace in C++?

Q12

Which statement correctly compares `struct` and `class` in C++?

Q13

Which memory area is typically used for local variables inside a function?

Q14

A copy constructor is generally called when:

Q15

Shallow copy becomes risky mainly when a class contains:

Q16

Which statement correctly describes copy assignment?

Q17

Inside a non-static member function, `this` points to:

Q18

A static data member in a class is:

Q19

Which statement about static member functions is correct?

Q20

A friend function is mainly used when:

Q21

Which statement about inline functions is most accurate?

Q22

Which option best describes a deep copy?

Q23

Compared with `malloc()`, `new` in C++ additionally:

Q24

Which statement about heap memory is correct?

Q25

Inheritance in C++ is mainly used to:

Q26

Which type of inheritance is supported in C++ but often discussed carefully because it can introduce ambiguity?

Q27

Polymorphism in C++ means:

Q28

Which is an example of runtime polymorphism in C++?

Q29

A virtual function is primarily used to enable:

Q30

Why is a virtual destructor important in a polymorphic base class?

Q31

A pure virtual function is declared using:

Q32

A class with at least one pure virtual function is usually:

Q33

Object slicing occurs when:

Q34

Which statement correctly compares overloading and overriding?

Q35

If a base pointer points to a derived object and the called method is not virtual, C++ generally uses:

Q36

Which statement about abstract classes is correct?

Q37

Templates in C++ are mainly used for:

Q38

Which statement best describes a class template?

Q39

The STL mainly provides:

Q40

Which container is usually the default choice when you need a dynamic array with fast random access?

Q41

Which statement about `list` is correct?

Q42

Which container keeps keys sorted by default?

Q43

The average-case strength of `unordered_map` is:

Q44

An iterator in C++ is best understood as:

Q45

A lambda expression in C++ is:

Q46

The main purpose of `auto` in C++ is to:

Q47

Which statement about smart pointers is correct?

Q48

Which smart pointer type represents exclusive ownership?

Q49

RAII in C++ mainly means:

Q50

The Rule of Five extends the Rule of Three by adding:

Q51

Which statement best describes move semantics?

Q52

Which statement about `const` member functions is correct?

Q53

Which null-pointer literal should be preferred in modern C++?

Q54

Which cast performs runtime-checked downcasting in a polymorphic class hierarchy?

Q55

Which cast is the lowest-level and should usually be used very carefully?

Q56

In a `vector`, `size()` returns:

Q57

In a `vector`, `capacity()` refers to:

Q58

Which statement about C++ exceptions is correct?

Q59

Which is an example of a compile-time error?

Q60

Which is more likely to be a runtime error?

Q61

Which item is normally stored in a Process Control Block (PCB)?

Q62

In a multithreaded process, which resource is typically private to each thread rather than shared by all threads?

Q63

What is a common drawback of the many-to-one user-thread model?

Q64

A child process has finished execution, but its parent has not yet collected its exit status. What is the child process at this point?

Q65

Why does copy-on-write make fork() efficient in many real systems?

Q66

Which IPC mechanism usually gives the lowest overhead after setup when large amounts of data must be exchanged frequently?

Q67

Two threads increment a shared counter without synchronization and sometimes produce the wrong final value. What is the most precise name for this problem?

Q68

Which of the following is NOT one of the classic requirements for a correct critical-section solution?

Q69

Which statement best describes an orphan process?

Q70

In a typical process-based memory protection model, what usually happens if one thread in a process causes an unhandled segmentation fault?

Q71

If exact CPU burst times were known in advance, which scheduling algorithm minimizes average waiting time?

Q72

What is the most likely effect of choosing an extremely small time quantum in Round Robin scheduling?

Q73

Which technique is commonly used to reduce starvation in priority scheduling?

Q74

Which scheduling policy is the preemptive counterpart of Shortest Job First?

Q75

What best describes the convoy effect in FCFS scheduling?

Q76

Which metric measures the time from job arrival until the process first gets CPU service?

Q77

In non-preemptive priority scheduling, what happens if a higher-priority process arrives while a lower-priority process is currently running?

Q78

What is the defining idea of a multilevel feedback queue scheduler?

Q79

Which scheduling goal is most directly emphasized by Round Robin in a time-sharing system?

Q80

Which formula correctly defines turnaround time for a process?

Q81

Which statement best describes internal fragmentation?

Q82

A TLB miss means which of the following?

Q83

When does a page fault occur in a demand-paged system?

Q84

Belady's anomaly is classically associated with which page-replacement algorithm?

Q85

Which algorithm is commonly used as a practical approximation to LRU?

Q86

Which memory-allocation technique is more likely to suffer from external fragmentation?

Q87

Which situation most strongly suggests that a system is thrashing?

Q88

What is the main idea behind copy-on-write after fork()?

Q89

Which statement correctly describes demand paging?

Q90

If TLB lookup time is 10 ns, memory access time is 100 ns, and the TLB hit ratio is 80%, what is the effective access time assuming one memory access on a hit and two on a miss?

Q91

Which set contains all four Coffman conditions required for deadlock?

Q92

In a resource-allocation graph where each resource type has exactly one instance, what does a cycle imply?

Q93

What does it mean for the system to be in a safe state?

Q94

What key information does the Banker's algorithm require in advance from each process?

Q95

Which policy most directly prevents circular wait?

Q96

If processes are forced to request all needed resources at once before execution begins, which deadlock condition is being attacked most directly?

Q97

Which statement best distinguishes deadlock detection from deadlock avoidance?

Q98

Which of the following is a legitimate deadlock recovery technique after deadlock has been detected?

Q99

In a system where some resource types have multiple instances, a cycle in the resource-allocation graph means:

Q100

How does livelock differ from deadlock?

Q101

If the original filename of a file is deleted but another hard link to the same file still exists, what happens to the file data?

Q102

In a Unix-like file system, where is the filename typically stored?

Q103

What is the primary purpose of journaling in a file system?

Q104

What is a major drawback of contiguous file allocation?

Q105

Which allocation method most naturally supports direct access through an index structure rather than following a chain?

Q106

Which statement best describes C-SCAN disk scheduling?

Q107

Which RAID level provides mirroring rather than striping with parity?

Q108

What does it mean to mount a file system?

Q109

If two directory entries refer to the same inode, what is the relationship between them?

Q110

What is the main purpose of the page cache or file cache in an operating system?

Q111

Which statement correctly compares a system call with a library call?

Q112

Which action generally requires kernel-mode privilege?

Q113

Which statement best distinguishes an interrupt from an exception?

Q114

Which is a common advantage of a microkernel compared with a monolithic kernel?

Q115

What happens when a thread performs wait(P) on a counting semaphore whose value is currently 0?

Q116

Which statement about mutexes is most accurate?

Q117

What is the main benefit of DMA in I/O systems?

Q118

What is the primary role of the bootloader?

Q119

Why is spooling useful for devices such as printers?

Q120

What is a key advantage of memory-mapped file I/O through mmap-style mechanisms?

Q121

Python is commonly described as:

Q122

Dynamic typing in Python means:

Q123

Which statement about Python execution is most accurate?

Q124

Which type is immutable in Python?

Q125

Which type is best suited for storing unique values only?

Q126

A Python dictionary stores data as:

Q127

In Python, `==` checks:

Q128

In Python, `is` is mainly used to compare:

Q129

Which of the following is mutable?

Q130

A shallow copy of a nested list mainly means:

Q131

Why is a mutable default argument risky in Python?

Q132

What is the usual safe default when you want an optional list parameter?

Q133

In Python, `*args` collects extra positional arguments into a:

Q134

In Python, `**kwargs` collects extra keyword arguments into a:

Q135

A lambda function in Python is best described as:

Q136

Which construct is most directly used to create a list in a compact loop-like form?

Q137

Which statement correctly compares an iterable and an iterator?

Q138

A generator in Python is useful mainly because it:

Q139

Which keyword is used to make a function behave as a generator?

Q140

Which statement best describes Python argument passing?

Q141

A decorator in Python is mainly used to:

Q142

When we say functions are first-class objects in Python, we mean they can:

Q143

Which keyword is used inside a nested function to modify a variable from the nearest enclosing function scope?

Q144

Which statement about `global` is correct?

Q145

In an instance method, `self` refers to:

Q146

What is the main purpose of `init()`?

Q147

Which method type receives `cls` as its first automatic argument?

Q148

Which method type receives neither `self` nor `cls` automatically?

Q149

Inheritance in Python allows a class to:

Q150

Method overriding happens when:

Q151

Python supports multiple inheritance, which means:

Q152

MRO in Python stands for:

Q153

Why is `super()` commonly used?

Q154

Duck typing in Python emphasizes:

Q155

In Python, a single leading underscore in an attribute name usually means:

Q156

Abstraction in Python is mainly about:

Q157

Which keywords are directly associated with Python exception handling?

Q158

`raise` in Python is used to:

Q159

Why is `assert` not a full replacement for `raise` in production logic?

Q160

A context manager is commonly used with:

Q161

Why is the `with` statement preferred for file handling?

Q162

The GIL in CPython mainly affects:

Q163

For CPU-bound work in CPython, which approach is often preferred over threading?

Q164

Which statement best compares threads and processes in Python?

Q165

Python memory management in CPython mainly relies on:

Q166

Reference counting means an object can usually be cleaned up when:

Q167

A module in Python is usually:

Q168

Why do we use `if name == "main"`?

Q169

Unpacking in Python is used to:

Q170

Which expression is an example of slicing?

Q171

A dataclass in Python is most useful when:

Q172

What does `@property` mainly help you do?

Q173

If `nums = [1, 2]`, what does `nums.append([3, 4])` do?

Q174

Which statement correctly compares `append()` and `extend()`?

Q175

Which statement about `sort()` and `sorted()` is correct?

Q176

`repr()` is mainly intended for:

Q177

A closure in Python is:

Q178

Compared with a list comprehension, a generator expression usually:

Q179

EAFP in Python means:

Q180

LBYL in Python means:

Q181

SQL is primarily used to:

Q182

A primary key should:

Q183

Which statement best describes a foreign key?

Q184

Which option correctly compares `WHERE` and `HAVING`?

Q185

Which statement about `DELETE`, `TRUNCATE`, and `DROP` is correct?

Q186

In SQL, `NULL` means:

Q187

Which condition is correct for checking missing values in SQL?

Q188

`GROUP BY` is mainly used to:

Q189

An `INNER JOIN` returns:

Q190

A `LEFT JOIN` returns:

Q191

A self join is used when:

Q192

`UNION` differs from `UNION ALL` because `UNION`:

Q193

A subquery is:

Q194

Which statement best compares `IN` and `EXISTS`?

Q195

A CTE is introduced using:

Q196

To list all customers even if they have no matching orders, which join is most appropriate?

Q197

Which of the following is an aggregate function?

Q198

If a column contains nulls, `COUNT(column)` will:

Q199

`COUNT(*)` returns:

Q200

A window function differs from `GROUP BY` mainly because it:

Q201

Which function gives every row a unique running number even when values tie?

Q202

Which function leaves gaps in ranking after tied values?

Q203

Which tool is commonly used to assign labels like 'High', 'Medium', and 'Low' in query output?

Q204

If you only want unique rows in the query result, which keyword is most direct?

Q205

Normalization is mainly used to:

Q206

1NF mainly requires that:

Q207

Denormalization is usually considered when:

Q208

A composite key uses:

Q209

Which of the following is a constraint?

Q210

Which statement best describes a view?

Q211

An index is mainly created to:

Q212

Which statement about indexes is correct?

Q213

A transaction is best described as:

Q214

In ACID, atomicity means:

Q215

Which ACID property is most directly about committed data surviving a crash?

Q216

Which command makes current transaction changes permanent?

Q217

Which command is used to undo uncommitted transaction work?

Q218

A `SAVEPOINT` is useful because it:

Q219

Isolation levels mainly control:

Q220

Operating System MCQ questions with answers