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Full Discussion: C header file and extern
Top Forums Programming C header file and extern Post 302851859 by tornow on Tuesday 10th of September 2013 12:11:34 AM
Old 09-10-2013
Thanks. Your explanation and example makes it more clear (also thanks for pointing out it may not be best praxis, but for now i just try to understand the general idea).

I think you say that: header files are (or can be ) used _instead of declaring the variable foo as extern in File2 and File3. foo is defined in File1 (and storage is set aside for it). File1 includes myheader.h too, and if foo is declared (File2 and File3) or defined (File1) is decided by the #ifndef Mainfile and #define Mainfile in File1.

I read in §The C Programming langauge"; (As "C A modern approach" was not clear on the subject) and in chapter 1 "External variables and scope" (page 33 for me) it says the following (or that is what i understand):
- a definition creates a variable and sets aside storage
- a declaration only announces the nature of a variable
- extern says that the definition is elsewhere and only declares
- header files include declarations, not definitions
Is both correct (What i understood of your post and what i understood of the book)?

I think i am getting closer to understand it. Let me rethink and read again.Really thanks.
 

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PAPS(1) 						      General Commands Manual							   PAPS(1)

NAME
paps - UTF-8 to PostScript converter using Pango SYNOPSIS
paps [options] files... DESCRIPTION
paps reads a UTF-8 encoded file and generates a PostScript language rendering of the file. The rendering is done by creating outline curves through the pango ft2 backend. OPTIONS
These programs follow the usual GNU command line syntax, with long options starting with two dashes (`-'). A summary of options is included below. --landscape Landscape output. Default is portrait. --columns=cl Number of columns output. Default is 1. Please notice this option isn't related to the terminal length as in a "80 culums terminal". --font=desc Set the font description. Default is Monospace 12. --rtl Do right to left (RTL) layout. --paper ps Choose paper size. Known paper sizes are legal, letter and A4. Default is A4. Postscript points Each postscript point equals to 1/72 of an inch. 36 points are 1/2 of an inch. --bottom-margin=bm Set bottom margin. Default is 36 postscript points. --top-margin=tm Set top margin. Default is 36 postscript points. --left-margin=lm Set left margin. Default is 36 postscript points. --right-margin=rm Set right margin. Default is 36 postscript points. --gutter-width=gw Set gutter width. Default is 40 postscript points. --help Show summary of options. --header Draw page header for each page. --markup Interpret the text as pango markup. --lpi Set the lines per inch. This determines the line spacing. --cpi Set the characters per inch. This is an alternative method of specifying the font size. --stretch-chars Indicates that characters should be stretched in the y-direction to fill up their vertical space. This is similar to the texttops behaviour. AUTHOR
paps was written by Dov Grobgeld <dov.grobgeld@gmail.com>. This manual page was written by Lior Kaplan <kaplan@debian.org>, for the Debian project (but may be used by others). April 17, 2006 PAPS(1)
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