C Language, Q:printf() and scanf()....

Clark S. Cox, I
#1 / 4

Q:printf() and scanf()....

Quote:

> Hi.
> an ordinary function's prototype such as add() function would be:

[snip]

Quote:

> but what's the prototype of standard function like prinf() or scanf()??
> because I think they can have variant number of parameters.

Well, the prototype for printf is:

int printf(const char *format, ...);

Quote:

> and when the compiler work with this parameters, how does it do that?

Well, read the FAQ, < http://www.*-*-*.com/ ~scs/C-faq/s15.html>,
specifically 15.4.

--
Clark S. Cox, III

http://www.*-*-*.com/

Mon, 28 Apr 2003 03:00:00 GMT

Chaos09
#2 / 4

Q:printf() and scanf()....

Hi.
an ordinary function's prototype such as add() function would be:

int add(int, int);

so when I call it, it would be like:

int main()
{
int a;
a = add(10, 20);

Quote:

}

but what's the prototype of standard function like prinf() or scanf()??
because I think they can have variant number of parameters. like:

printf("%d %d", 10, 20);
printf("Hello world!");

and when the compiler work with this parameters, how does it do that?

Tue, 29 Apr 2003 11:48:13 GMT

mike burrel
#3 / 4

Q:printf() and scanf()....

Quote:

> but what's the prototype of standard function like prinf()

int printf(char const *, ...);

Quote:

> or scanf()??

int scanf(char const *, ...);

Quote:

> and when the compiler work with this parameters, how does it do that?

look in your manual for the va_start, va_arg and va_end macros, which all
deal with the va_list (variadic argument list) type. they are defined in
the standard header file stdarg.h

if you have any further questions, post again.

--
/"\ m i k e b u r r e l l

X AGAINST HTML MAIL,

Tue, 29 Apr 2003 12:05:55 GMT

Derek Callawa
#4 / 4

Q:printf() and scanf()....

Quote:

> Hi.
> an ordinary function's prototype such as add() function would be:
> int add(int, int);
> so when I call it, it would be like:
> int main()
> {
> int a;
> a = add(10, 20);
> }
> but what's the prototype of standard function like prinf() or scanf()??

You can find these in stdio.h.

Quote:

> because I think they can have variant number of parameters. like:
> printf("%d %d", 10, 20);
> printf("Hello world!");
> and when the compiler work with this parameters, how does it do that?

By taking advantage of variable argument lists. You can find a description
of these at http://man-pages.net/linux/man3/stdarg.3.html, but K&R's is
probably better.

--

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Tue, 29 Apr 2003 12:07:01 GMT