The API Biography - Take 2 - The PC and API revolution

If you have been one of the lucky ones to see or use a computer that started with the picture on the left - smile for you have witnessed the commencement of the API revolution. If you have ever read the book below or referenced it to write a line of code, pat yourself on the back. For you, have helped made the API revolution possible. And if you are reading this post, be proud. For you are now powered and have the knowledge to take it forward!



MACs have always been much more cooler than Windows based PCs, but the more than 90% share of PCs that existed for long has been largely there because of the thousands (now millions) of application software available on Windows. And these applications themselves have been possible due to the extensive set of APIs that Microsoft OS provides. Ok, lets talk more!! Whenever you create an app or software for an Operating System (OS), lets say Windows (or Mac), you need to talk and instruct the OS to do anything you want. This entire talking is done through APIs. For instance, to create the main window of application, there in an API called CreateWindow which takes a bunch of options (called parameters) like title of window, location, size, style etc. Every application running on windows needs to call this API to show it's first screen. The OS responds back to the API call with a Handle to the window which the application then uses through a device context (it's Ok to ignore this term!) to do more things like DrawText (another API) or CreateFile (yet another API). 

The ever (in)famous Message Box that you see here is also created using an API called MessageBox. And so are all the menus, toolbars, buttons and check boxes. These APIs have grown from few hundreds in the initial version of Windows to several thousands today. In fact, many applications have now started providing their own APIs so that other applications can integrate with them. The term plugins or extensions that you hear sometimes are these second level applications which are built using APIs created and provided by the core first level application. For instance, Acrobat provides APIs and a plugin architecture for other 3rd party vendors to integrate. You see, APIs are viral!

Here are some more keywords for further reading. On Windows, these APIs for the longest time were called Win32 APIs. In MAC, they are provided by the Carbon and Cocoa Frameworks. In Acrobat, there is a complete API SDK for building plugins.