sound capture program

hello,

if I want to make an application that will capture the sound from:
- everything that goes to headphones
- everything that comes form mic, line-in

give me some pointers where I have to start ? any system services that allow that ? what devices I have to read from (/dev/what) etc. anything

Check out Audio HiJack it may be able to do the things you what. I have used it to rip audio from music DVD's.