Linux run time levels
 

how many levels of softwares exists in a typical Linux Operating System.Is it possible develop OS which consists of audio player which directly interacts with the core hardware

not sure your question is very clear. Are you asking for how to make your software interact directly with the kernel? Or are you asking how many run levels linux has in which case that would be 7. 0 - 6 but the only usuable is 2 - 5 which range from single user to multi user to multi user with gui.

Kernel is the core. Using ALSA or OSS it is possible. Pulse audio is another option(?)
You can also go lower...but that will be kernel level

http://howto.wikia.com/wiki/Howto_co...nel/sound/core

...I think you want a custom kernel

Thanks for your post. how many levels(how the conversion is done in various phases) we need to make a audio player to interact with core hardware of the system.