How does asynchronous programming differ from multithreading?

Asynchronous programming and multithreading are different concepts, although they are often used together.

• Multithreading is the ability of a program to execute multiple threads simultaneously, each of which can run in parallel on different CPU cores. It is about physical or logical parallel execution of code.

• Asynchronous programming is a way of organizing code where operations that may take time (such as input/output, network requests) are performed without blocking the main thread. Asynchrony allows continuing execution without waiting for the operation to complete, and the result is handled later via callbacks, tasks, or async/await.

Example in C#:

// Asynchronous method, non-blocking thread
async Task<string> DownloadAsync(string url)
{
    using var client = new HttpClient();
    string result = await client.GetStringAsync(url);
    return result;
}

Here, the method does not create a new thread but uses .NET's asynchronous capabilities to efficiently wait for the result.

Thus, asynchrony is about non-blocking waiting, and multithreading is about parallel execution of code.