>   I'm assigned to investigate on building a program that will be 'service' 
> for other programs in netbsd.  First of all, I don't know how to develop a 
> 'service' program, so is there any good sources that tell me that?

It's not clear to me what you mean by a "service" program.  Perhaps it
is a NT term?  Can you explain some more, and perhaps provide an
example of what you're talking about?

Some suggestions:

1. read W. Richard Steven's "Advanced Programming in the Unix
   Environment".  This is the best book I know of about programming on
   Unix systems.

2. look at the NetBSD source for similar programs to the "service" you
   want to write, and see how they are implemented

3. look at the daemon(3) function (but I'm really guessing here!)

You'll not find NetBSD too different from other Unix systems for
writing applications.

Good luck,

Giles