Multitasking vs Multithreading vs Multiprocessing

Modern operating systems support multitasking (mainly preemptive multitasking), multithreading and multiprocessing (including symmetric multiprocessing and heterogeneous multiprocessing). But what are they? Are they different? What do software engineers need to know about these different paradigms? Let me explain!

#garyexplains

[leixun]

*My takeaways:*
1. Multitasking on a single-core CPU - CPU time is divided for different programs, and program executions are switched instead of being executed one after another, but there is no real speed improvement 0:36
2. Multithreading on a single-core CPU - Codes in the same program were executed in "parallel", and threads are switched instead of being executed one after another, but there is no real speed improvement 2:59
3. Multiprocessing - this is when we have more than one CPU core, and we can do real multitasking and multithreading (i.e. executing programs and threads on different cores at the same time) 4:18
4. An experiment on Raspberry Pi with a single-core CPU 4:55
5. An experiment on Raspberry Pi with a quad-core CPU 7:23

[TheSar]

Another fabulous representation of a complex concept.
The lab test you used to explains this was superb - well done Sir!

[VeselinMarkovic]

Excellent as always - clear, short and simple. Hyperthreading next? I reckon most people think that a processor with hyperthreading is twice as fast as one without it, which isn't true; it's more efficient, yes - but not twice as much. A video on RT systems would be quite interesting. Keep making excellent vids, Mr Sims! 👍

[galenblack]

Gary, I have been trying to explain this, for years, to people that know nothing of multitasking. You explained it perfectly. Thankyou.

[nimrodlevy]

Please do video on multitasking!!! Many Many thanks in advance!!

[bkdev]

I like how Gary will try to explain with practical example, it needs dedication.

[fuzz]

Professor Sims - brilliant clarity as one comes to expect from the Chair of the Department.

[senthilanantha]

Your explanation was simple, straight forward, practical and very effective. 👍

[venkataravieluri]

Really looking forward for your dedicated video on multitasking.

[BrendanGeels]

Excellent video!
I agree with Mr. Marković below, a video on RT systems or just RT OS's would be great!

[sarenodev]

This video alone asnswers a lot of my years old question. The explanation is excellent.

[alvaroj]

This was so good Gary bro, especially the visual explanation with raspberry pi. Thank you so much!

[moy]

Ive literally been trying to wrap my head around this concept for 2 weeks now and you managed to clear things up int 10min. Thanks for this great video!!!!

[ashfaqrahman]

You can't be so good at explaining things with such cute looks. God bless Gary.

[jayde]

Thanks for let us understand Multithreading. Because we had a little twist there.

[tanmoypaul]

A video discussing multitasking in detail would be most welcome!

[SamerTabbal]

So a CPU can have Multi-Cores, each Core can Multi-Task, and each Task can Multi-Thread.

[subhoghosal]

Waiting for a multitasking video. It seem interesting. OS remain always a nightmare to me, but you explain so clearly. Looking for the above mentioned video.

[suvetar]

Great video Gary, I for one would love to see another video drilling into multitasking, the difference between pre-emptive and co-operative multitasking - but more specifically *how* it happens, I know the task-scheduler runs in a lower ring in modern CPUs, but how did this manage this on old CPUs, how does it stop the operation of one task, save it's state and continue with another? What impact does this have on complicated computations that for example might be in the middle of a complex branch prediction stage? The task scheduler has to save state and presumably do something to the Cpu to stall or complete its instruction pipeline. I think I understand it in a technical fashion but I couldn't explain it to someone, so I'd love your delicate touch on this complex subject!


Thanks again for sharing this video :)

[tudorhategan]

Can't find a better explanation.
GREAT ONE!!