I've found this stack-overflow question which describes how we can make the compiler.

[saswatsamal]

Question: How to Create a Web App to Compile and Run Java/C/PHP Code Online?
Link- Click Here

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The approach that I found most relevant:

According to a MVC pattern applied to a web architecture, is something like this:

A web application client-side, which allows the user to insert some code, possibly leveraging Javascript for early syntactic check
A server endpoint, receiving the inserted code as input from the client

The sequence of operations could be:

1. Server-side, the input is transformed into the appropriate structure for the target programming language, e.g. a Java class or a C module.
2. Possibly, more context is defined (e.g. a classpath).
3. Then, if the language is compiled, the compiler is invoked (e.g. javac or gcc). This can happen in several ways, e.g. exec in C or Runtime.getRuntime().exec in Java. Otherwise the code can be deployed on a server or some simulators can be run and passed the code.
4. Subsequently, the code is executed and output is intercepted (e.g. by directioning the console output to a file or just leveraging the target language infrastructure, like in this example). The execution can happen through command line (e.g. java) or via other tools (e.g. curl for running a deployed php code as it was a client browser accessing it)
5. Last step for the server is to send back the intercepted output to the client in a readable format, e.g. HTML. As an alternative, if you used Java, you could go for Applet, which doesn't change the basic architecture.

[Saswat7101]

Okk this is good for starters