15 Atomicity & Memory questions from the Concurrency bank, written for Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd.
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A.an instruction that forbids the compiler and hardware from reordering memory accesses across it, enforcing an ordering point
B.the guarantee that a write performed by one thread becomes observable to other threads rather than lingering in a private cache
C.a variable qualifier ensuring every access touches main memory and is not cached or reordered, used for visibility rather than atomicity of compound updates
D.an action that completes indivisibly as a single step, so other threads observe it as either fully done or not started, never partial
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2. Which term means: "an action that completes indivisibly as a single step, so other threads observe it as either fully done or not started, never partial"?
Junior
A.Atomic operation
B.Visibility
C.Happens-before
D.Memory barrier
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3. Which statement is correct?
Junior
A.Atomic operation — an instruction that forbids the compiler and hardware from reordering memory accesses across it, enforcing an ordering point
B.Atomic operation — the partial ordering guarantee that if one action precedes another in this relation, the first's effects are visible to the second
C.Atomic operation — the guarantee that a write performed by one thread becomes observable to other threads rather than lingering in a private cache
D.Atomic operation — an action that completes indivisibly as a single step, so other threads observe it as either fully done or not started, never partial
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4. What is Memory barrier?
Senior
A.the partial ordering guarantee that if one action precedes another in this relation, the first's effects are visible to the second
B.the guarantee that a write performed by one thread becomes observable to other threads rather than lingering in a private cache
C.an instruction that forbids the compiler and hardware from reordering memory accesses across it, enforcing an ordering point
D.a variable qualifier ensuring every access touches main memory and is not cached or reordered, used for visibility rather than atomicity of compound updates
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5. Which term means: "an instruction that forbids the compiler and hardware from reordering memory accesses across it, enforcing an ordering point"?
Senior
A.Memory barrier
B.Visibility
C.Volatile
D.Atomic operation
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6. Which statement is correct?
Senior
A.Memory barrier — the guarantee that a write performed by one thread becomes observable to other threads rather than lingering in a private cache
B.Memory barrier — an instruction that forbids the compiler and hardware from reordering memory accesses across it, enforcing an ordering point
C.Memory barrier — a variable qualifier ensuring every access touches main memory and is not cached or reordered, used for visibility rather than atomicity of compound updates
D.Memory barrier — the partial ordering guarantee that if one action precedes another in this relation, the first's effects are visible to the second
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7. What is Visibility?
Mid
A.a variable qualifier ensuring every access touches main memory and is not cached or reordered, used for visibility rather than atomicity of compound updates
B.the guarantee that a write performed by one thread becomes observable to other threads rather than lingering in a private cache
C.an instruction that forbids the compiler and hardware from reordering memory accesses across it, enforcing an ordering point
D.the partial ordering guarantee that if one action precedes another in this relation, the first's effects are visible to the second
Answer + AI explanation with Pro
8. Which term means: "the guarantee that a write performed by one thread becomes observable to other threads rather than lingering in a private cache"?
Mid
A.Memory barrier
B.Visibility
C.Happens-before
D.Volatile
Answer + AI explanation with Pro
9. Which statement is correct?
Mid
A.Visibility — the partial ordering guarantee that if one action precedes another in this relation, the first's effects are visible to the second
B.Visibility — the guarantee that a write performed by one thread becomes observable to other threads rather than lingering in a private cache
C.Visibility — an action that completes indivisibly as a single step, so other threads observe it as either fully done or not started, never partial
D.Visibility — a variable qualifier ensuring every access touches main memory and is not cached or reordered, used for visibility rather than atomicity of compound updates
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10. What is Happens-before?
Senior
A.the partial ordering guarantee that if one action precedes another in this relation, the first's effects are visible to the second
B.a variable qualifier ensuring every access touches main memory and is not cached or reordered, used for visibility rather than atomicity of compound updates
C.an action that completes indivisibly as a single step, so other threads observe it as either fully done or not started, never partial
D.an instruction that forbids the compiler and hardware from reordering memory accesses across it, enforcing an ordering point
Answer + AI explanation with Pro
11. Which term means: "the partial ordering guarantee that if one action precedes another in this relation, the first's effects are visible to the second"?
Senior
A.Atomic operation
B.Volatile
C.Visibility
D.Happens-before
Answer + AI explanation with Pro
12. Which statement is correct?
Senior
A.Happens-before — a variable qualifier ensuring every access touches main memory and is not cached or reordered, used for visibility rather than atomicity of compound updates
B.Happens-before — an instruction that forbids the compiler and hardware from reordering memory accesses across it, enforcing an ordering point
C.Happens-before — the guarantee that a write performed by one thread becomes observable to other threads rather than lingering in a private cache
D.Happens-before — the partial ordering guarantee that if one action precedes another in this relation, the first's effects are visible to the second
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13. What is Volatile?
Mid
A.an action that completes indivisibly as a single step, so other threads observe it as either fully done or not started, never partial
B.an instruction that forbids the compiler and hardware from reordering memory accesses across it, enforcing an ordering point
C.the guarantee that a write performed by one thread becomes observable to other threads rather than lingering in a private cache
D.a variable qualifier ensuring every access touches main memory and is not cached or reordered, used for visibility rather than atomicity of compound updates
Answer + AI explanation with Pro
14. Which term means: "a variable qualifier ensuring every access touches main memory and is not cached or reordered, used for visibility rather than atomicity of compound updates"?
Mid
A.Memory barrier
B.Visibility
C.Volatile
D.Atomic operation
Answer + AI explanation with Pro
15. Which statement is correct?
Mid
A.Volatile — a variable qualifier ensuring every access touches main memory and is not cached or reordered, used for visibility rather than atomicity of compound updates
B.Volatile — an action that completes indivisibly as a single step, so other threads observe it as either fully done or not started, never partial
C.Volatile — the partial ordering guarantee that if one action precedes another in this relation, the first's effects are visible to the second
D.Volatile — the guarantee that a write performed by one thread becomes observable to other threads rather than lingering in a private cache
Answer + AI explanation with Pro
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