|Simple Runtime Framework by Example|
|Written by Alexey Lyashko|
|Wednesday, 06 June 2012|
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These days we are surrounded by different software frameworks. Java, and .NET to name but two, and, there are many more. Have you ever wondered how they work or have you ever wanted or needed to implement one?
This article explores a simple, even trivial, runtime framework.
Note: The source code given in this article is for example purposes only. I know that this framework is far from being perfect, therefore, this article is not a howto or tutorial - just an explanation of principle. Error checks are omitted on purpose. You want to implement a real framework - do it yourself, including error checks.
Now, to let's get to business.
Wikipedia gives the following identification for the term "Software Framework":
A software framework is a universal, reusable software platform used to develop applications, products and solutions. Software Frameworks include support programs, compilers, code libraries, an application programming interface (API) and tool sets that bring together all the different components to enable development of a project or solution.
As you can see, software framework is quite a complex thing. However, let's simplify it and see how it basically work.
Figure 1 may give you a good understanding of what a Software Framework is and what role it performs. Put simply it is a shim between the user application and the Operating System.
There are at least two types of Software Frameworks:
The basics of building a simple virtual machine is covered in this article, so I will only give a brief explanation here.
Our VM in this example will consist of the following components:
The name of the function speaks for itself. This is the first function of the framework implementation which gains control. In this particular case, it does not have too many things to do - initialization of the virtual CPU and execution of the command interpreter, until the user application exits (signals the framework to terminate the execution).
It is a common practice to implement a framework as a DLL (dynamic link library), for example, mscoree.dll - the core of the .Net framework. I do not see any reason to reinvent the wheel, therefore, this framework will be implemented as a DLL as well.
All is fine, you may say, but how should we pass the compiled pseudo assembly code to the framework?
Well, I bet, most of you know how to do that. In case you don't - no worries, just keep reading.
|Last Updated ( Wednesday, 06 June 2012 )|