Asynchronous vs synchronous execution, what does it really mean? [closed]

Answer 1

You are confusing Synchronous with Parallel vs Series. Synchronous mean all at the same time. Syncronized means related to each othere which can mean in series or at a fixed interval. While the program is doing all, it it running in series. Get a dictionary...this is why we have unsweet tea. You have tea or sweetened tea.

Answer 2

Yes synchronous means at the same time, literally, it means doing work all together. multiple human/objects in the world can do multiple things at the same time but if we look at computer, it says synchronous means where the processes work together that means the processes are dependent on the return of one another and that's why they get executed one after another in proper sequence. Whereas asynchronous means where processes don't work together, they may work at the same time(if are on multithread), but work independently.

Answer 3

When you execute something synchronously, you wait for it to finish before moving on to another task. When you execute something asynchronously, you can move on to another task before it finishes.

That being said, in the context of computers this translates into executing a process or task on another "thread." A thread is a series of commands (a block of code) that exists as a unit of work. The operating system can manage multiple threads and assign a thread a piece ("slice") of processor time before switching to another thread to give it a turn to do some work. At its core (pardon the pun), a processor can simply execute a command, it has no concept of doing two things at one time. The operating system simulates this by allocating slices of time to different threads.

Now, if you introduce multiple cores/processors into the mix, then things CAN actually happen at the same time. The operating system can allocate time to one thread on the first processor, then allocate the same block of time to another thread on a different processor. All of this is about allowing the operating system to manage the completion of your task while you can go on in your code and do other things.

Asynchronous programming is a complicated topic because of the semantics of how things tie together when you can do them at the same time. There are numerous articles and books on the subject; have a look!

Answer 4

Use an example of instructions for making a breakfast

1. Pour a cup of coffee.
2. Heat up a pan, then fry two eggs.
3. Fry three slices of bacon.
4. Toast two pieces of bread.
5. Add butter and jam to the toast.
6. Pour a glass of orange juice.

If you have experience cooking, you'd execute those instructions asynchronously. you'd start warming the pan for eggs, then start the bacon. You'd put the bread in the toaster, then start the eggs. At each step of the process, you'd start a task, then turn your attention to tasks that are ready for your attention.

Cooking breakfast is a good example of asynchronous work that isn't parallel. One person (or thread) can handle all these tasks. Continuing the breakfast analogy, one person can make breakfast asynchronously by starting the next task before the first completes. The cooking progresses whether or not someone is watching it. As soon as you start warming the pan for the eggs, you can begin frying the bacon. Once the bacon starts, you can put the bread into the toaster.

For a parallel algorithm, you'd need multiple cooks (or threads). One would make the eggs, one the bacon, and so on. Each one would be focused on just that one task. Each cook (or thread) would be blocked synchronously waiting for bacon to be ready to flip, or the toast to pop.

Reference from Asynchronous programming concepts