[TriLUG] a C question

[Paul D. Boyle]

Greg wrote:
> 
> I'm teaching myself C and I'm confused about something (and I'm only on day 3 
> of "teach yourself in 21 days" so I'm still doing really basic things).
> 
> The following program complies and does what I expect it to (return a number 
> to STDOUT):
> 
> #include<stdio.h>
> 
> int fav_num;

This doesn't need to be global.  Put this in the body of main().

> 
> int main(void)
> {
> 
> 	printf("What is your favorite number?\n");
> 	scanf("%d", &fav_num);

It is always a good idea to see what scanf() returns.  If you do this
with your code you will see that the scanf() function scanned 0 items
when you enter text.  This means input was available but the conversion
wasn't done.

> 	printf("\n\nYour favorite number is %d\n\n", fav_num);
> 	return 0;
> }
> 
> If I try to enter text instead of a number the program returns 0, not the 
> text.  The issue seems to be %d gizmo which I'm guessing can only be a 
> numeric, not text.  Or is the problem the way I've declared the variable 
> fav_num?  Is there a different way to declare a variable when it is text?  Or 
> is the issue %d?

If you want to read in character data use a character array or a pointer to 
char which points to dynamically allocated memory.

The comp.lang.c newsgroup is a good place to ask C questions (but do read the
FAQ for the group first, it is quite informative).

If you want read text you use a combination of fgets() and sscanf()
(note the 'ss').  The comp.lang.c FAQ explains how to use these functions.

Good Luck,

Paul

-- 
Paul D. Boyle			    |	boyle at laue.chem.ncsu.edu
Director, X-ray Structural Facility |	phone: (919) 515-7362
Department of Chemistry - Box 8204  |	FAX:   (919) 515-5079
North Carolina State University     |	http://www.xray.ncsu.edu  
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