The Preprocessor; Using the #include statement

[tiger6425]

I am doin the 13.3 program in Programming in C by Stephen G. Kochran. I put out the program like it supposed to.

/* Program to illustrate the use of the #include statement
   Note: This program assumes that definitions are
   set up in a file called metric.h             */

#include <stdio.h>
#include "metric.h"

int main (void)
{
	float liters, gallons;

	printf ("*** Liters to gallons ***\n\n");
	printf ("Enter the number of liters: ");
	scanf  ("%f", &liters);

	gallons = liters * QUARTS_PER_LITER / 4.0;
	printf ("%g liters = %g gallons\n", liters, gallons);

	return 0;
}

and I gettting the errors:


1>------ Build started: Project: Program 13.3, Configuration: Debug Win32 ------
1>Compiling...
1>13-3.c
1>f:\c programming\program 13.3\program 13.3\13-3.c(6) : fatal error C1083: Cannot open include file: 'metric.h': No such file or directory
1>Build log was saved at "file://f:\C Programming\Program 13.3\Program 13.3\Debug\BuildLog.htm"
1>Program 13.3 - 1 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

I have Microsoft Visual C++ 2008 compiler, how come it doesn't know what #include "metric.h" is?

[kermit]

Do you have metric.h in the same directory as .c source file?

[tiger6425]

I don't know if I do, how do you know if its in the directory, its probably not in there, how do you insert metric.h in the same directory?

[Bayint Naung]

Where is your source file ( .c file) ? Is it :\c programming\program 13.3\program 13.3\13-3.c(6) :? Then the header file matric.h should be also in that folder.

[Elysia]

This is normal file system business we're talking about here. Like you have a directory where you store all your music, your pictures, your videos, whatever. Likewise your project is in a directory and your source file, as well. Put the .h file in the very same directory as the source file. Then it will work.

[tiger6425]

I added the metric.h in the source files like in the image. The program still doesn't work, what should I correct to make the program work?

[Elysia]

It seems that QUARTS_PER_LITER is not defined anywhere. Considering this should be an example, it might help if you showed the contents of the header file metric.h?
Otherwise you'd have to define QUARTS_PER_LITER manually. What it's supposed to be, however, I don't know.

[tiger6425]

I looked back in the book and it said I had to define the measurements in a attached file which I attached and had nothing in the file. In the metric.h file below I put in:

#define INCHES_PER_CENTIMETER 0.394
#define CENTIMETERS_PER_INCH  1 / INCHES_PER_CENTIMETER

#define QUARTS_PER_LITER   1.057
#define LITERS_PER_INCH	   1 / QUARTS_PER_LITER

#define OUNCES_PER_GRAM    0.035
#define GRAMS_PER_OUNCE    1 / OUNCES_PER_GRAM

Then I runned the program with start without debugging and got the program to work. Thank you Elysia so much , I am new to Preprocessors, giving me that clue to show the metric.h file gave me the idea which I looked back into the book and told me I had to put the #define statements in the metric.h file to have the program understand where the information was coming from.

[Elysia]

Hmm. Well, the point of headers are that you can put information inside them that can be shared between different source files. If two or more files need those defines, then it's a good idea to put them in the header. Including a header simply pastes the information inside it into the source file.