hello,
i have just started Socket programming and i come across functions
inet_addr() which converts IP address to unsigned long
and inet_ntoa() which converts unsigned long to IP address

but dont understand on what formula/principle they do these conversions
say for a given ip address can i expect what unsigned long number its going to give and vice versa.

one more thing:
i am writting a program , just to know how the above functions work but the difficulty is
i need to declare various structure variable , but how to know the exact names of the structures
i mean whether the structure is given in_addr_t or in_addr or some other name

can i see the structures and and its contents i am so confused.

please help me.
this is bit urgent and i want to learn it quickly.