Synchronous VS Asynchronous Programming with Examples

Updated on April 3, 2022

Synchronous and Asynchronous programming are the two terms that make a beginner confuse the most. But you don’t have to worry about this anymore.

In this article, I will discuss in-depth about synchronous and asynchronous programming, how they work and what are the main differences between synchronous and asynchronous programming.

After reading this article, you will know how and where to use them efficiently inside your code.

Synchronous programming performs tasks one by one by blocking the main thread. It only starts a new task if the previous one completes. On the other hand, asynchronous programming can perform multiple tasks at the same time in parallel without blocking the main thread. But both have their own use cases in programming.

Tips: A thread is a single end-to-end line or worker that performs specific tasks or handles requests in the programming.

Now we have a brief idea about both the techniques. But now I will discuss how they work in real-world scenarios with practical examples.

Let’s start

summery infographic about synchronous vs asynchronous programming with examples

How Synchronous Programming Works

At the beginning of programming, codes were used to run synchronously. That is why most languages follow this technique while executing the code.

As we know synchronous application blocks the main thread to run the code line by line. So, to make the application faster it uses multiple threads available in the system.

Therefore, the system or computer that has more power and resources can execute code quicker.

But the main problem is if all the available threads in a system are busy then code execution becomes slow. The program waits until any thread gets free then it moves on with the rest of the code.

The programming language that follows the synchronous system and uses multiple threads is known as multi-threaded language. Like, Python, C, C++, etc.

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How Asynchronous Programming Works

Asynchronous programming came into existence to solve some problems that synchronous programming had.

This type of programming uses only one single thread to execute code. That is why it makes sure that the main thread never gets blocked.

When a request comes to an asynchronous program, it starts to handle it line by line like the synchronous program.

But the real difference is if the program needs to do something that may take a few seconds, the program performs that task in the background without waiting for the task to finish.

Meanwhile, it starts to handle other requests. When the pending task completes in the background, a signal comes to the main thread.

Then it carries on with the request and sends the response to the client or completes the task.

The programming language that follows the asynchronous system and uses a single thread is known as a single-threaded language like JavaScript.

I know it is quite complicated to understand for a beginner. But to make it easy for you, I am giving some real-world examples in the next section.

I think these examples will clear away all the confusions you have.

Examples of Synchronous and Asynchronous Programming

Suppose you are in a restaurant waiting to place your order. There is a total of 10 people are waiting and the restaurant has 5 waiters.

If the restaurant works synchronously, 5 waiters will take orders from 5 customers and wait to complete those orders. They will not do anything else. So the other 5 customers have to wait to place their orders.

Here 10 customers represent 10 requests and 5 waiters represent 5 threads. 5 threads can handle only 5 requests at the same time. Other requests have to wait.

On the other hand, if the restaurant works asynchronously, 1 waiter can take all the orders from 10 customers.

The waiter will now wait to finish any order. He will take orders one by one and transfer that to the kitchen.

When someone’s food is ready in the kitchen, he will receive a signal to deliver that food to the right customer.

Here, a single thread is receiving requests one by one and requests are being processed in the background like food are getting ready in the kitchen. When any request is successfully processed then that thread sends the response.

Another example with a real-world web server.

In this example, we will see how a web server handles requests when it uses a synchronous or asynchronous programming method.

Difference between synchronous and asynchronous programming with example

In the above picture, we can see that when a server that runs synchronously gets 2 requests, it handles them one by one. The server is searching data in a database for request 1 and request 2 is waiting.

But in an asynchronous server, it is searching for data in the background. In the meantime, the server starts working on request 2.

When the server finds data from the database, it sends a response for request 1. That’s why it is taking very little time than the previous server.

I hope that it is clear to you the main difference between synchronous and asynchronous programming and how they perform tasks.

Language Support for Synchronous and Asynchronous Programming

Most of the server-side languages execute code line by line dependently. They complete the current task before starting the next one. So, they are synchronous by default.

But with the recent updates, most of these languages support asynchronous programming like Golang. But none of them are asynchronous by default.

Nodejs is the runtime that introduced asynchronous programming on the server-side. Nodejs by default is asynchronous and uses a single thread to execute code.

Also Read: Best Guide on Dynamic Import in JavaScript for Importing Modules

Pros and Cons of Synchronous and Asynchronous Programming

At a first glance, you might think asynchronous programming is best for anything but it's not. Both technologies have their pros and cons and also have their use cases.

To know a clear-cut idea about their strength and weakness and when you should use them, let’s look at their pros and cons.

Pros of Asynchronous Programming

  • It can run concurrent IO operations.
  • A server can handle more requests using few resources.
  • It improves application performance and responsiveness.
  • Asynchronous application is highly scalable as it uses fewer resources.
  • As asynchronous language handle tasks separately, one slow request does not affect other requests.

Cons of Asynchronous Programming

  • This method takes more time to process a large amount of data.
  • It is difficult to execute code that is highly dependent on each other.
  • Very few programming languages support asynchronous methods by default.
  • It is not good to perform CPU-intensive operations because it only uses one thread.
  • Applications that use asynchronous loading are bad for SEO (Search Engine Optimization).

Pros of Synchronous Programming

  • It can process large amounts of data efficiently for its multi-threading.
  • It is better to perform CPU-intensive operations because it uses multiple threads.
  • As this method execute code line by line, it is good to handle highly dependent code.
  • As most the languages use synchronous method, you have more options to choose from.
  • Applications that use synchronous loading are good for SEO. Search engines can crawl web pages easily.

Cons of Synchronous Programming

  • It cannot run concurrent IO operations.
  • Loading time for an application can be slow.
  • One slow request can affect other requests because it blocks the thread.
  • It handles a smaller number of requests compared to the asynchronous method.
  • A huge amount of resources and computing power may require if the request increases.

Synchronous or Asynchronous Programming: Which Is Better?

From the above pros and cons, you can see that both methods work great in different scenarios. Therefore, it is very difficult to say one is better than another.

Still, both have their own use cares. It depends on your requirements and the type of application you are working on to decide when to use asynchronous programming and when to use synchronous programming.

If your application gets a large number of requests and does not have CPU-intensive operations like video editing, photo editing, and data processing then asynchronous programming is a great choice for you.

You can use Nodejs as your server-side technology. Asynchronous programming is also good for real-time data transfer like a chat application. It can transfer data very quickly.

On the other hand, if your application performs operations like video rendering, editing, or complex mathematical calculations then you should go for synchronous programming.

Because these operations are totally dependent on the CPU and its processing power. Therefore, you can choose C#, Golang, PHP, etc.

Wrapping It up

As I said before, every technology has its pros and cons. The way we build applications is changing every day. Every language is introducing new features to give developers more control.

That's why we need to keep ourselves updated with those changes so that we know about the latest features and differentiate those technologies.

I tried to give you detailed information so that you can understand the differences between synchronous and asynchronous programming. I hope now you can decide which technology you should choose according to your application requirements.

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