Re: A question on variable scope, coming from a relative beginner

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From	Keith Thompson <kst-u@mib.org>
Newsgroups	comp.lang.c
Subject	Re: A question on variable scope, coming from a relative beginner
Date	Thu, 12 Nov 2015 17:11:55 -0800
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Jon Rossen <jonr17@comcast.net> writes:
> Hi all, I'm fairly new to programming and have a question on the C 
> language with regards to variable scope, compilers and the 'extern' 
> keyword.  I'm using a couple of books that seem to have info that is not 
> in keeping with my results.  Here's a simple little trivial code example 
> that illustrates the question:
>
> #include <stdio.h>
>
> int x = 999;
> void print_value(void);
>
> int main(void)
> {
> 	extern int x;     // This entire statement is not necessary to
>                            // get the proper results, why??
>
> 	printf("%d\n", x);
> 	print_value();
>
> 	return 0;
> }
>
> void print_value(void)
> {
> 	extern int x;    // This obviously is
> 	printf("%d\n", x);
> }
>
> Result: 999
>          999

The "extern int x;" declaration (not statement) is not necessary either
in main or in print_value.  The file-scope definition of x is visible in
both functions.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

Thread

A question on variable scope, coming from a relative beginner Jon Rossen <jonr17@comcast.net> - 2015-11-12 13:32 -0800
  Re: A question on variable scope, coming from a relative beginner John Gordon <gordon@panix.com> - 2015-11-12 21:57 +0000
    Re: A question on variable scope, coming from a relative beginner Jon Rossen <jonr17@comcast.net> - 2015-11-12 16:06 -0800
      Re: A question on variable scope, coming from a relative beginner James Kuyper <jameskuyper@verizon.net> - 2015-11-12 19:33 -0500
        Re: A question on variable scope, coming from a relative beginner Jon Rossen <jonr17@comcast.net> - 2015-11-12 20:22 -0800
          Re: A question on variable scope, coming from a relative beginner James Kuyper <jameskuyper@verizon.net> - 2015-11-13 08:08 -0500
  Re: A question on variable scope, coming from a relative beginner Richard Heathfield <rjh@cpax.org.uk> - 2015-11-12 21:57 +0000
    Re: A question on variable scope, coming from a relative beginner Jon Rossen <jonr17@comcast.net> - 2015-11-12 18:47 -0800
      Re: A question on variable scope, coming from a relative beginner James Kuyper <jameskuyper@verizon.net> - 2015-11-12 22:19 -0500
        Re: A question on variable scope, coming from a relative beginner Jon Rossen <jonr17@comcast.net> - 2015-11-12 22:05 -0800
          Re: A question on variable scope, coming from a relative beginner Richard Heathfield <rjh@cpax.org.uk> - 2015-11-13 07:10 +0000
          Re: A question on variable scope, coming from a relative beginner James Kuyper <jameskuyper@verizon.net> - 2015-11-13 08:33 -0500
            Re: A question on variable scope, coming from a relative beginner Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-13 12:24 -0800
            Re: A question on variable scope, coming from a relative beginner Keith Thompson <kst-u@mib.org> - 2015-11-14 11:58 -0800
              Re: A question on variable scope, coming from a relative beginner James Kuyper <jameskuyper@verizon.net> - 2015-11-14 15:27 -0500
  Re: A question on variable scope, coming from a relative beginner Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-12 14:00 -0800
    Re: A question on variable scope, coming from a relative beginner Richard Heathfield <rjh@cpax.org.uk> - 2015-11-12 23:55 +0000
  Re: A question on variable scope, coming from a relative beginner Keith Thompson <kst-u@mib.org> - 2015-11-12 17:11 -0800
    Re: A question on variable scope, coming from a relative beginner Jon Rossen <jonr17@comcast.net> - 2015-11-12 20:39 -0800
  Re: A question on variable scope, coming from a relative beginner Jon Rossen <jonr17@comcast.net> - 2015-11-12 20:38 -0800
    Re: A question on variable scope, coming from a relative beginner Keith Thompson <kst-u@mib.org> - 2015-11-12 22:13 -0800
      Re: A question on variable scope, coming from a relative beginner Jon Rossen <jonr17@comcast.net> - 2015-11-15 21:17 -0800

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