Operating systems · 1 min
Why concurrency and parallelism are not the same
Learn how concurrency and parallelism differ, how CPU cores are utilized, and why synchronisation like mutexes is required.
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The quiz
What is the difference between concurrency and parallelism?
- They are the same
- Concurrency always makes a program faster
- Parallelism needs only one core
- Concurrency is dealing with several tasks in overlapping time, possibly by switching on one core; parallelism is actually running tasks at the same instant on several cores
Show the answer
D. Concurrency is dealing with several tasks in overlapping time, possibly by switching on one core; parallelism is actually running tasks at the same instant on several cores
Transcript
Calling concurrency and parallelism the same thing gets you rejected immediately in interviews.
Concurrency is dealing with several tasks in overlapping time, while parallelism means running tasks at the same instant on several cores.
Handling slow web connections on a single thread is concurrent, but splitting heavy computation across eight cores is pure parallelism.
Now the part most people miss: concurrency always requires synchronisation like mutexes, whether running on single or multiple cores.
Interviewers often ask if concurrency requires multiple cores, but dealing with tasks in overlapping time can happen on one core.
Always upgrade your answer by highlighting overlapping time on one core versus running tasks at the exact same instant.
Pause the video right now and pick the correct option between A, B, C, or D on your screen.
Option D is correct because concurrency deals with tasks in overlapping time, while parallelism actually runs tasks at the same instant on several cores.
Save this comparison table before your placement drive and practice these operating system interview concepts on InternDoor right now.
