Using Multiple files

File 1 - main.c

/***************************************************************
*                                                              *
*  Author: Brenda Sonderegger                                  *
*  Last modified: Sept. 21, 1999                               *
*  Purpose: provide an example of using multiple files within  *
*           a project.                                         *
*  Functions: main()                                           *
*             others that are specific to this application     *
*                                                              *
*  Functions called: get_int() in "myio_c.h"                   *
*                                                              *
***************************************************************/
 
#include <stdio.h>
#include "myio_c.h"

int main(void)
{
  int i = 0;

  while (i != 5)
  {
    printf("\n5 to quit ");
    get_int(&i);
  }

  return (0);
}

File 2 - header file named myio_c.h

#ifndef _MYIO_C_H
#define _MYIO_C_H

#include <stdio.h>
#include <ctype.h>

/*****************************************************
*                                                    *
* File Name: myio_c.h                                *
* Author: Brenda Sonderegger (all functions)         *
* Contents:                                          *
*    get_int()                                       *
*    get_int_low()                                   *
*    get_int_bound()                                 *
*                                                    *
*****************************************************/  

  /*****************************************************
  * void get_int(int *value)                           *
  * Author: Brenda Sonderegger                         *
  * Last Modified: Sept. 22, 1998                      *
  * Parameters: single address                         * 
  * Return value: none                                 *
  * Side Effect: puts an integer value into the memory *
  *              location specified by the address and *
  *              if an error occurs, the input stream  *
  *              is emptied                            *
  * Description: guarantees that the input value is an *
  *              integer.  Inputs of a, 23c, 2.4 are   *
  *              all considered to be illegal          *
  *****************************************************/
void get_int(int *value);



  /*****************************************************
  * void get_int_low(int *value, int low)              *
  * Author: Brenda Sonderegger                         *
  * Last Modified: Sept. 16, 1998                      *
  * Parameters: single address, and single integer     * 
  * Return value: none                                 *
  * Side Effect: puts an integer value into the memory *
  *              location specified by the address that*
  *              if guaranteed to be greater than or   *
  *              equal to the low value                *
  * Description: guarantees that the input value is an *
  *              integer greater than or equal to low  *
  * Functions called: get_int()                        *
  *****************************************************/
void get_int_low(int *value, int low);



  /*****************************************************
  * void get_int_bound(int *value, int low, int high)  *
  * Author: Brenda Sonderegger                         *
  * Last Modified: Sept. 16, 1998                      *
  * Parameters: single address, and two integers       * 
  * Return value: none                                 *
  * Side Effect: puts an integer value into the memory *
  *              location specified by the address that*
  *              if guaranteed to be greater than or   *
  *              equal to the low value and less than  *
  *              or equal to the high value            *
  * Description: guarantees that the input value is an * 
  *              integer greater than or equal to low  *
  *              and less than or equal to high        *
  * Functions called: get_int()                        *
  *****************************************************/
void get_int_bound(int *value, int low, int high);
 
#endif

File 3 - source code for all prototypes in myio_c.c

#include "myio_c.h"

/*****************************************************
*                                                    *
* File Name: myio_c.c                                *
* Author: Brenda Sonderegger (all functions)         *
* Contents:                                          *
*    get_int()                                       *
*    get_int_low()                                   *
*    get_int_bound()                                 *
*                                                    *
*****************************************************/  

  /*****************************************************
  * void get_int(int *value)                           *
  * Author: Brenda Sonderegger                         *
  * Last Modified: Sept. 22, 1998                      *
  * Parameters: single address                         * 
  * Return value: none                                 *
  * Side Effect: puts an integer value into the memory *
  *              location specified by the address and *
  *              if an error occurs, the input stream  *
  *              is emptied                            *
  * Description: guarantees that the input value is an *
  *              integer.  Inputs of a, 23c, 2.4 are   *
  *              all considered to be illegal          *
  *****************************************************/
void get_int(int *value)
{
 
   scanf("%d", value);
   /** the robust version should be substituted for this **/

}



  /*****************************************************
  * void get_int_low(int *value, int low)              *
  * Author: Brenda Sonderegger                         *
  * Last Modified: Sept. 16, 1998                      *
  * Parameters: single address, and single integer     * 
  * Return value: none                                 *
  * Side Effect: puts an integer value into the memory *
  *              location specified by the address that*
  *              if guaranteed to be greater than or   *
  *              equal to the low value                *
  * Description: guarantees that the input value is an *
  *              integer greater than or equal to low  *
  * Functions called: get_int()                        *
  *****************************************************/
void get_int_low(int *value, int low)
{
   do
   {
     get_int(value);
     if (*value < low)
       printf("\nValue must be >= %d.  Try again.\n", low);
   }
   while (*value < low);
}


  /*****************************************************
  * void get_int_bound(int *value, int low, int high)  *
  * Author: Brenda Sonderegger                         *
  * Last Modified: Sept. 16, 1998                      *
  * Parameters: single address, and two integers       * 
  * Return value: none                                 *
  * Side Effect: puts an integer value into the memory *
  *              location specified by the address that*
  *              if guaranteed to be greater than or   *
  *              equal to the low value and less than  *
  *              or equal to the high value            *
  * Description: guarantees that the input value is an *
  *              integer greater than or equal to low  *
  *              and less than or equal to high        *
  * Functions called: get_int()                        *
  *****************************************************/
void get_int_bound(int *value, int low, int high)
{
   do
   {
     get_int(value);
     if ((*value < low) || (*value > high))
       printf("\nValue must be between %d and %d, inclusive.  Try again.\n", 
                 low, high);
   }
   while ((*value < low) || (*value > high));
} 
 

Compiling multiple files

• PC environment - usually you are using some Integraded Development Environment (IDE) that provides the idea of a project. When you set up a project, you actually are setting up the program to compile all the parts (files) of your program into an executable whole. Simply specifying the project option and following the directions should be sufficient.
• Unix - you usually don't have an IDE which gives you a project option so you have to provide it for yourself. The most effective method is to use makefiles (there is a lab on this). The idea here is to create a program (make) which when run, will gather all the information about the various files in your project and make a single executable from them. The language used to create the make is a scripting language that has some odd syntax (MUST TAB - can't use spaces at certain places.) The nice part is that once the make is created correctly, it only recompiles the files that have been modified since the last time the program was "made". This saves compile time, especially if you have several files and/or some very large files.
• Unix - if you haven't learned to do makefiles, then you can take the brute force method below.

      %cc file1.c file2.c file3.c 
      

  You get a single executable (a.out) in this case; however, each file will be compiled from scratch whether or not it has been modified since the last compile. This is not as efficient as a make but "works".

  For the listed files in this example, you would use

      %cc main.c myio_c.c
      

  
  For a group of files that have included the math.h library, use

      %cc main.c file1.c -lm