Can someone xplain FLUSH in strings?

Hi,
I know the basic purpose of FLUSH but want to have a deeper understanding of it..the code for FLUSH (ing) in C is this..can someone please explain..
{
#define FLUSH while(getchar() != '\n')
char month[10];

printf("Please enter a month");
scanf("%9s", month);
FLUSH;
}

I understand everything but the definition and as to how does the call work..please help..thanks
A :)

when you complie your code the compiler will replace the word FLUSH with it's definition.
So there is no call, your code will look like

Code:

---

printf("Please enter a month");
scanf("%9s", month);
while(getchar() != '\n');

---

Quote:

---

#define FLUSH while(getchar() != '\n')

---

thats ugly, use a function designed for flushing scanf instead

PHP Code:

---

#define     FLUSH fflush(stdin) 


---

This is undefined, and therefore not guaranteed to work:
>#define FLUSH fflush(stdin)

Read about it here

>thats ugly

no need to call names...

That is one of the most common defines I have seen in programming. Not to mention it always works.

Umm..thanks for your varied answers but could someone stick w/ the code I've mentioned and explain what
while(!(getchar()....) does?? Please..Thanks..
Honestly, your answers confused me a bit more..it would be great if someone explained it clearly..
Thanks again
A :)

>explain what while(!(getchar()....) does??
while ( getchar() != '\n' );

What this does is read characters from stdin until a newline is reached. Since a newline usually means the end of input it is assumed that once this loop exits there will be nothing left in the input buffer. It's very useful for clearing the newline left in the buffer by calls to scanf.

-Prelude

Code:

---

{
#define FLUSH while(getchar() != '\n')
char month[10];

printf("Please enter a month");
scanf("%9s", month);
FLUSH;
}

---

When scanf() reads input, it will take upto 9 characters into the variable month. If the user enter 50 characters, the remaining 41 stay in the input buffer. scanf() will also leave the new line character in the buffer.

The while loop containing getchar() simply eats the characters in the buffer until a new line is reached. That way all the extra characters are ignored.

If you didn't do the FLUSH call, the next time your prog did a read from the keyboard, it would get the users input from earlier, which would probably give undesired results.

[EDIT] Doh! beaten again.:D [/EDIT]

Go go go!!!:D

Thanks guys SOOOOOOOOOO much!
The last 3 (umm..maybe not the one before this but the 2 before that one) helped me a lot..thanks!!
A :)