Help on program

[rewclaus]

Hi ALL. Maybe someone can give me a hand. I was trying to write a CD collection program, and I got stuck while compiling the program. I came up with an error that said:

" c:\documents and settings\ishbu\desktop\c\cd3.c: line 84: illegal dereference 'add_it(cditem)'
aborting compile "


the whole code is here...so maybe someone can take a look in their spare time.

Also one other thing of note...in the switch process, the program never breaks when it is supposed to. I found that out by just testing bits of the code at a time.

Here it is:

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

struct cd_struct
  { char title[30];
    char artist[30];
  };

FILE *fp;

#define MAX 50
#define BELL '\x07'
#define FILENAME "CDs.dat"


void main(void);
void disp_menu(void);
void clear_sc(void);
void enter_cd(void);
void print_cd(void);
void err_msg(char err_msg[]);
void add_it(struct cd_struct cditem);
void pause_sc(void);
void pr_data(struct cd_struct cditem);


/******************************/
void main(void)
{
  struct cd_struct list[MAX];
  int num;
  
 do
    { disp_menu();
      scanf(" %d", &num);
      
      switch (num)
      { case 1 : { enter_cd();
                     break; }
        case 2 : { print_cd();
                     break; }
        case 3 : { break; }
        default : { err_msg("*** You need to enter");
                    printf(" 1 through 3 ***");
                    break; }
      }
     } while (num!=3);
     return;
}

/******************************/
void disp_menu()
{
  clear_sc();
  printf("\t\t*** CD LIST MANAGER ***\n");
  printf("\t\t    ---------------\n\n\n\n");
  printf("Do you want to:\n\n\n");
  printf("\t1. Add a CD to your collection\n\n\n");
  printf("\t2. Print info of CDs in your collection\n\n\n");
  printf("\t3. Exit this program\n\n\n");
  printf("What is your choice? ");
  return;
}

/******************************/
void clear_sc()
{
 int ctr;
 for(ctr=0;ctr<25;ctr++)
    { printf("\n"); }
 return;
}

/******************************/
void enter_cd(void)
{
  struct cd_struct cditem;
  char answ;
  do
  { fflush(stdin);
    printf("\n\n\n\n\nWhat is the TITLE? ");
    gets(cditem.title);
    printf("Who is the Artist? ");
    gets(cditem.artist);
    add_it(cditem);
    printf("\n\nDo you want to enter another CD? (Y/N) ");
    answ=getchar();
    getchar();
   }while (toupper(answ)=='Y');

   return;
}

/******************************/
void print_cd(void)
{
  struct cd_struct cditem;
  int s, linectr=0;

  s = sizeof(struct cd_struct);
  if((fp=fopen(FILENAME, "r"))==NULL)
     { err_msg("*** Read error--ensure file exists ***");
       return 0; }
  do
    { if(fread(&cditem, sizeof(struct cd_struct),1, fp)!=s)
     { if(feof(fp))
        { break; }
     }
       if (linectr>20)
       { pause_sc;
         linectr=0; }
       pr_data(cditem);
       linectr+=4;
    }while (!feof(fp));     
  fclose(fp);
  printf("\n- End of Collection -");
  pause_sc();
  return;
}

/******************************/
void err_msg(char err_msg[])
{
  printf("\n\n%s\n", err_msg);
  printf("%c", BELL);
  return;
}

/******************************/
void add_it(struct cd_struct cditem)
{
  if((fp = fopen(FILENAME, "a"))==NULL)
     { err_msg("*** Disk error--please check disk drive ***");
       return 0; }
  fwrite(&cditem, sizeof(cditem), 1, fp);
  fclose(fp);
  return;
}

/******************************/
void pause_sc()
{
  char ans;
  fflush(stdin);
  printf("\nPress the Enter key to continue...");
  ans=getchar();
  fflush(stdin);
  return;
}

/******************************/
void pr_data(struct cd_struct cditem)
{
  printf("\nTitle    :  %-30s\n", cditem.title);
  printf("Artist    :  %-30s\n", cditem.artist);
  return;
}

[quzah]

Read this.
Then read this.
While you're at it, read this.

That'll get you started.

Quzah.

[Draco]

try experimenting with the brackets in your switch statement

[Emmanuel Delaha]

Here it is: <...>

First of all, you sould learn how to configure your compiler for a better analysis :

Compiling MAIN.C:
Error MAIN.C 28: main must have a return type of int
Warning MAIN.C 63: 'list' is declared but never used
Warning MAIN.C 105: Code has no effect
Warning MAIN.C 122: Void functions may not return a value
Warning MAIN.C 135: Code has no effect
Warning MAIN.C 145: Both return and return with a value used
Warning MAIN.C 162: Void functions may not return a value
Warning MAIN.C 166: Both return and return with a value used
Warning MAIN.C 178: 'ans' is assigned a value that is never used

That said, there are several flaws in your code, mainly a bad use of the input functions. I recommend to use solid input functions based on fgets() or fgetc(), and to stick them into some personal library.

Here is a revisited version of your code using such a library code (ful references given further).

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

#include "ed/inc/io.h"

struct cd_struct
{
   char title[30];
   char artist[30];
};

#define MAX 50
#define BELL '\a'
#define FILENAME "CDs.dat"

/******************************/
static void clear_sc (void)
{
#if 1
   /* MS-DOS/Windows */
   system ("cls");
#else
   /* Unix-like */
   system ("clear");
#endif
}

/******************************/
static void disp_menu (void)
{
   clear_sc ();
   printf ("\t\t*** CD LIST MANAGER ***\n"
           "\t\t    ---------------\n\n\n\n"
           "Do you want to:\n\n\n"
           "\t1. Add a CD to your collection\n\n\n"
           "\t2. Print info of CDs in your collection\n\n\n"
           "\t3. Exit this program\n\n\n"
           "What is your choice? ");
}

/******************************/
static void err_msg (char err_msg[])
{
   printf ("\n\n%s\n", err_msg);
   printf ("%c", BELL);
}

/******************************/
static int add_it (struct cd_struct const *p_cditem)
{
   int ok = 1;
   FILE *fp = fopen (FILENAME, "ab");

   if (fp == NULL)
   {
      err_msg ("*** Disk error--please check disk drive ***");
      ok = 0;
   }
   else
   {
      fwrite (p_cditem, sizeof *p_cditem, 1, fp);
      fclose (fp);
   }
   return ok;
}

/******************************/
static void enter_cd (void)
{
   struct cd_struct cditem;
   int answ;
   do
   {
      printf ("\n\n\n\n\nWhat is the TITLE? ");
      get_s (cditem.title, sizeof cditem.title);
      printf ("Who is the Artist? ");
      get_s (cditem.artist, sizeof cditem.artist);
      add_it (&cditem);
      printf ("\n\nDo you want to enter another CD? (Y/N) ");
      answ = get_c ();
   }
   while (toupper (answ) == 'Y');
}

/******************************/
static void pause_sc (void)
{
   printf ("\nPress the Enter key to continue...");
   (void) get_c ();
}

/******************************/
static void pr_data (struct cd_struct const *p_cditem)
{
   printf ("\nTitle    :  %-30s\n", p_cditem->title);
   printf ("Artist    :  %-30s\n", p_cditem->artist);
}

/******************************/
static int print_cd (void)
{
   int ok = 1;
   struct cd_struct cditem;
   int linectr = 0;
   size_t s = sizeof (struct cd_struct);
   FILE *fp = fopen (FILENAME, "rb");

   if (fp == NULL)
   {
      err_msg ("*** Read error--ensure file exists ***");
      ok = 0;
   }
   else
   {
      do
      {
         if (fread (&cditem, sizeof (struct cd_struct), 1, fp) != s)
         {
            if (feof (fp))
            {
               break;
            }
         }

         if (linectr > 20)
         {
            pause_sc ();
            linectr = 0;
         }
         pr_data (&cditem);
         linectr += 4;
      }
      while (!feof (fp));
      fclose (fp);
      printf ("\n- End of Collection -");
      pause_sc ();
   }
   return ok;
}

/******************************/
int main (void)
{
   int num;

   do
   {
      disp_menu ();
      {
         long x;
         get_l (&x);
         num = (int) x;
      }

      switch (num)
      {
      case 1:
         {
            enter_cd ();
            break;
         }
      case 2:
         {
            print_cd ();
            break;
         }
      case 3:
         {
            break;
         }
      default:
         {
            err_msg ("*** You need to enter");
            printf (" 1 through 3 ***");
            break;
         }
      }
   }
   while (num != 3);
   return;
}

The missing code is here:

http://mapage.noos.fr/emdel/clib.htm
Module IO

Feel free to ask for details.

Note also that storing raw structures is not portable in C. It only works by chance on a very closed system (same machine, same compiler, same options, same phases of moon...)

The usual way is to use a text format.