Clearing the Input buffer

I've already read the FAQ entery wich is located here so please don't mention it and focus on answering my question.

Code:

#include<stdio.h>

int main()
{
int number;
char ch , string[100];

     printf("Input a number : \n");
     scanf("%d", &number);
       
     while( ch = getchar() != '\n' && ch != EOF);  

     printf("Input a string : \n");
     fgets(string, sizeof(string), stdin);

     printf("You've entered %d and %s\n", number , string);

return 0;
}

now my questions are :
[list=1][*]Why doesn't the program wait for the user to input a character with getchar() in the line :
while( ch = getchar() != '\n' && ch != EOF);
[*] I've read on some sites that scanf() leaves the '\n' on the input buffer. If thats right , then why doesn't fgets() leaves one too??
[*]why doesn't fgets() wait for input if the '\n' was in stdin??[/list=1]


thanks for your time.

1) ch should be int to be big enough to hold EOF.
2) fgets puts \n at the end of the string, before \0.
3) fgets reads a line. that is everything before \n.

Building on previous answers:

>Why doesn't the program wait for the user to input a character with getchar()
Because != binds more tightly than assignment in the precedence table. What your code is doing is taking the character returned by getchar and testing it against '\n', then assigning the result of that boolean expression to ch. Because EOF is a negative quantity, a boolean value (0 or 1) will never match it. The code should instead be:

Code:

while ( ( ch = getchar() ) != '\n' && c != EOF )
  ;

>I've read on some sites that scanf() leaves the '\n' on the input buffer. If thats right , then why doesn't fgets() leaves one too??
Because fgets reads the newline and stores it in the buffer that you pass to it if the input is smaller than the buffer and no errors occur. That's why you'll see most code using fgets remove a newline immediately after:

Code:

char *newline = strrchr ( buffer, '\n' );
if ( newline != NULL )
  *newline = '\0';

>why doesn't fgets() wait for input if the '\n' was in stdin??
Because encountering a newline is one of fgets' termination conditions.

That was a great Prelude thanks alot. Thank you too Viaxd

One easy function to use is

flushall();

maybe from stdlib.h

>flushall();
Not standard. fflush ( NULL ) has the effect of flushing all open output streams, but if you were referring to flushing input streams, there is no standard function that does it for you.