Suppose that I construct my own programming language and my own compiler (for windows), I am free to use WINAPI like "CreateWindowEx"?

While the answer is no since you have to pay for the Windows OS so it's not free at all. But if we disregard this is not a free OS then once you've paid then you can use the API calls. If there is an issue with free or not, why not do your work on Linux or Android?

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.