> > These concepts are rather well talked about .. over the internet and
> > usenet, however, I cant find any clear explanation.

> > avcall, callback, trampoline, vacall, etc

> > I looked in a book of C programming, ie k&r and also the rationale for
> > C, an old copy and could not find any explanation.

> > I know that javascript books talk a lot about callbacks and there is
> > the style of programming involving writing callbacks and registering
> > them. Unfortunately, in the age when I took my C class, there was no
> > discussion along these lines.

> > Can anyone give clear definition, example, benefits, variations,
> > origin or citation to a paper where it originated and explained first,
> > as well as some modern text that does the better than most job of
> > illustrating it and its applications.

> "Callbacks" are a method of storing pointers to functions
> and exploiting them.

> I'm answering from comp.lang.c so one thing I would start with is to
> learn the concept of an ioctl(). It's one of the oldest ways to
> do this sort of thing. Just google for "device driver programming in
> linux" and follow some of the simpler examples. ioctl() is a pattern
> that occurs quite frequently, in and out of kernel/driver
> development.

> After that, just do plain old callbacks in 'C' - declare...

> //a typedef

> typedef void (*cbtype)(char *);

> // an array of them

> cbtype cbtab[3];

> // an initializer

> void set_cb(cbtype a,int idx)
> {
> ...

> }

> // and reference the callbacks

> void thing(char *s)
> {
> ...

> }

> ...

>    set_cb(thing,2);
>    cbtab[2]("Calling Elvis");

> --
> Les Cargill