I am new to Gumstix and Linux and I have troubles finding the appropriate way of coding for my programs.
For example I want to send some bytes from the serial port.
At the tutorials I read only about what pins one must change.
I found out that all devices are at /dev/. Where can I find what functions are there available for manipulating the devices from C. Should I write to the memory address that holds the register for example. Is there already a function tha does this job?

My question is general and refers to every device.
I just want to know the way I should start looking to find my answers.

Thank you,