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55. @Zenph: In this context, an entire block of code is what we're concerned with. Synchronous means that the block is executed at the same time (though, yes, the components are executed sequentially). Asynchronous means that the block is not all executed at the same time. – Adam Robinson.
The term asynchronous is related to thread execution. In an asynchronous model, when one task gets executed, you can switch to a different task without waiting for the previous task to get completed. Asynchronous programming helps us to achieve concurrency. Asynchronous programming in a multi-threaded environment is a way to achieve parallelism.
A synchronous client constructs an HTTP structure, sends a request, and waits for a response. An asynchronous client constructs an HTTP structure, sends a request, and moves on.
The difference between these two approaches is as follows: Synchronous way: It waits for each operation to complete, after that only it executes the next operation. For your query: The console.log() command will not be executed until & unless the query has finished executing to get all the result from Database.
Asynchronous: Asynchronous calls do not block (or wait) for the API call to return from the server. Execution continues on in your program, and when the call returns from the server, a "callback" function is executed. In Java, C and C#, "callbacks" are usually synchronous (with respect to a "main event loop").
3. Followup Q: The answer seems to make two different distinctions between the terms. First, the notification: non-blocking implies the application must check again later (polling) whereas async implies we can forget about it and rely on the framework/OS to notify us via callback or posting an event.
8. Asynchronous calls don't even need to occur on the same system/device as the one invoking the call. So if the question is, does an asynchronous call require a thread in the current process, the answer is no. However, there must be a thread of execution somewhere processing the asynchronous request.
You can have the same in Web APIs. Some APIs will return data in the body of the result of the calls and others will just return (e.g.) a 202 and then do something in the background (processing data, setting up a subscription).
Asynchronous means out of line, synchronous means in line. You can perform synchronous tasks and block multiple threads at once. If you are in a background thread and want to update a whole bunch of the user interface you call out to the main thread in a dispatch queue.
4. An asynchronous reset implies that you have a FF in your library that actually has a async clear (or async set) input. These tend to be a little larger than FFs that do not have these inputs, but this will vary depending on your libraries. These function such that as soon as the rest signal is asserted the Q of the FF will assume the reset ...