Program compatibility across different OS

[WindyDays]

So I really have a TON of questions surrounding this topic which Google doesn't give straight answers (or I haven't looked hard enough <[probably this]), but I guess I'll just ask the most important ones right now:

 

- What makes a program compatible for an OS?

  Do programs have to be re-coded completely to fit a different OS - e.g. are Windows, Linux and Mac versions of Firefox completely different?

  ... or is it just a simple optimisation that is done after the core OS is done?

 

- Is it harder to make some programs compatible than others?

   e.g. Would making a Windows game compatible for Mac/Linux/Other be harder than making a Windows browser compatible?

 

- Why aren't existing programs already compatible with all OS? Is it to do with the different kernels that operate on different OS?

  This also leads to: Is there a way to get around program compatibility without infringing patents so that we can see more OS's enter the market the end the Microsoft monopoly (yes, monopoly) on operating systems?

 

I don't think Microsoft is heading in the right direction right now, but because it is impossible to survive on Linux/Mac only for power users and enthusiasts which dominate this forum, is all hope in competition in the OS market lost?

 

By the way, as stable as Linux may be, I don't think that it's distro model and market model (or lack thereof) can make its way into mainstream, given the current circumstances. But that's just my opinion... feel free to discuss. I hope my nooby and overly long rambling isn't too overwhelming, thank you for reading!

[mvitkun]

@WindyDays

 

Linux may become more of a competitor to windows soon,because valve has shown interest in making Linux into a gaming platform,now it just need the triple A game developers support.

 

for power users (e.g video editing,3d design and animation,and other content creators)Linux is already a half decent option as there are Linux versions of business grade applications like Autodesk Maya/3DS Max.

and you can use Wine to use After Effects,Premiere Pro,Photoshop,Vegas Pro,etc.

 

Though I agree that for a majority of enthusiasts (gamers,content creators,etc) Windows is the first choice 

[WindyDays]

Although Linux is rapidly gaining support from big software companies, ultimately it is still Windows which will pretty much guarantee that your program will work on it. Enthusiasts often use programs which are private or niche due to diverse interests, and since these programs don't have a large enough market and usually not enough financial backup, developers will usually only code for Windows. Though a Valve[steam]/Linux distribution that supports all steam games would probably attract some consumers, I still believe the lack of a universal support for current (at release) programs is the fundamental problem and will basically kill any attention that the OS gets.

 

The way I see it, there are 3 parties that contribute to this problem:

OS developers: are deterred from making new OS's as you cannot(?) support existing programs and thus the new OS will not support any programs [or few if Linux].

Program developers: do not have the time/money to make multiple versions for OS's that may not be popular.

Market: will not buy or use new OS's are no programs work on them.

 

However the above information may be incorrect or misleading as I am unsure how this all works, hence why I am asking all of this to further my understanding of the situation. Thank you for all responses!