see , i found this code for scanf() in c .

int scanf(const char *format, ...) {
va_list args;
int rv;

va_start(args, format);
rv = scan(0, format, args);
va_end(args);

return rv;
}
static int scan(char **in, const char *fmt, va_list args)
{

// inside this block there is a line
while (EOF != (ch = scanchar(in)) && widht--)

}
static int scanchar(char **str) {
extern int getchar(void);
int ch;
if (str) {
ch = **str;
(*str)++;
return ch;

} else {
if ('\r' == (ch = getchar())) {
return EOF;
}
return ch;
}
}


so this is the whole process , but now can you tell me at start we are sending 0 in "in" , so what is the meaning of "in" in this program , and please clarify this with an example !

thanks , tushar

Always use [code] and [/code] tags when quoting source.
Passing NULL means default value, in this case reading from FILE stdin, instead of character-buffer.

Note: This program seems to implement scanf and sscanf together. In real-life cases scanf simply calls fscanf, and fscanf and sscanf are implemented together.

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means , please clarify more !

What is unclear?

please see this .....

take this simple example

scanf("%d",&a); when this line is executed .... so it need a input !

think about these two :-

1st line ....now if i do not enter any input ..... means we are entering o or null !

2nd line .... now if i enter 2 than it will read by characte buffer ..... according to you !

scanf calls scan (in=NULL), scan calls scanchar (in=NULL), and scanchar calls getchar; finally each call of getchar fetches a character from stdin.

If you are asking about the working of scanf: yes, a single scanf may result in reading zero or more lines from user, depending on the contents of buffers and the content of lines, which can be confusing; that's why many people prefer fgets+sscanf over scanf.

if .... in == NULL ... means you will read nothing & if == something than it will be read by getchar() , ok

but when will we get this "in == NULL ... means you will read nothing" condition ... according to me this condition will come when we press "ctrl+z" .... now what about your's ?

> if .... in == NULL ... means you will read nothing

I don't understand what are you trying to say here...

in==NULL means: read from stdin via getchar
in!=NULL means: read from memory (address=*in), then increment the pointer

> according to me this condition will come when we press "ctrl+z"

Ctrl+Z (in WinDos) means EOF, which causes getchar return -1. It has nothing to do with parameter 'in'.

thanx NevemTeve , you have beautiful mind , wow genius man !
.
i think you can play with "C"
.
hello another query , are you in social network , i want to stay in touch with you !

Off: No, I'm way too old for that

ha ha , why Mr. genius ! seriously i will take your whole knowledge !