Asynchronous programming

Asynchronous programming is a way of dealing with slow and unpredictable resources. Rather than waiting idle for resources to become available, asynchronous programs are able to handle multiple resources concurrently and efficiently. Programming in an asynchronous way can be challenging because it is necessary to deal with external requests that can arrive in any order, may take a variable amount of time, or may fail unpredictably. In this section, we will introduce the topic by explaining the main concepts and terminology as well as by giving an idea of how asynchronous programs work.

Waiting for I/O

A modern computer employs different kinds of memory to store data and perform operations. In general, a computer possesses a combination of expensive memory that is capable of operating at fast speeds and cheaper, and more abundant memory that operates at lower speeds and is used to store a larger amount of data.

The memory hierarchy is shown in the following diagram:

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