Thread: Problem with structured array.

Hi, I have problem with my coding. I'm using structured array.

For the first loop, everything is fine. Until, I enter 'Y' for second.
I enter the input as usual, and it is stuck at quantity. Suppose to be a runtime error. Anyone, could please enlighten the problem to me?

Thank you in advance.

Code:

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




struct product
{
    int id, quantity, reorder, i;
    char name[20];
    float price;
};


void gotoxy( int column, int line );
void addPRODUCT();
void displayPRODUCT();


COORD coord = {0, 0};




void gotoxy (int x, int y)
{
coord.X = x; coord.Y = y; // X and Y coordinates


SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE), coord);
}




void main()
{
addPRODUCT();
//displayPRODUCT();
}




void addPRODUCT()
{


    int i=0;
    struct product a[i];
    system("cls");


    char checker;




    do
    {
        gotoxy(20,5);
        printf("\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2 ADD PRODUCTS \xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2");


        gotoxy(20,15);
        printf("\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2");


        gotoxy(20,7);
        printf("Enter product ID : ");
        scanf(" %d", &a[i].id);


        gotoxy(20,9);
        printf("Enter product name : ");
        scanf(" %s", a[i].name);


        gotoxy(20,11);
        printf("Enter product quantity : ");
        scanf(" %d", &a[i].quantity);


        gotoxy(20,13);
        printf("Enter product price : ");
        scanf(" %f", &a[i].price);


        gotoxy(20,17);
        printf("Record saved!\n\n");


        gotoxy(20,19);
        printf("Do you want to enter new product? Y / N : ");
        scanf(" %c", &checker);
        checker = toupper(checker);


        i++;


        system("cls");
    }
    while(checker=='Y');


    }
}

Originally Posted by Salem

Having a member variable called i, and a loop variable called i, will surely lead to confusion.

Also, main returns and int, not void.

Originally Posted by GReaper

You have misunderstood how variable-length arrays work. In a nutshell, changing "i" won't change the size of the array after it was declared. You will have to use "realloc()" for that.

Alright. Now I am using the FILE to store the data.
Problem came after 1st loop where, run time error occur, after I put : fprintf(fp, "%d %s %d %f", a[i].id, a[i].name, a[i].quantity, a[i].price);

What is the problem actually ? Thanks in advance.

Code:

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


void gotoxy( int column, int line );
void addPRODUCT();
int displayPRODUCT();


struct product
{
    int quantity, reorder, i;
    char name[20];
    float price, id ;
};




COORD coord = {0, 0};


void gotoxy (int x, int y)
{
coord.X = x; coord.Y = y; // X and Y coordinates


SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE), coord);
}




/*void main()
{
addPRODUCT();
displayPRODUCT();
}*/




int main()
{
    FILE * fp;
    
    int i=0;
    struct product a[i];
    system("cls");
    
    char checker;


    do
    {
        gotoxy(20,5);
        printf("\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2 ADD PRODUCTS \xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2");


        gotoxy(20,15);
        printf("\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2");


        gotoxy(20,7);
        printf("Enter product ID : ");
        scanf(" %d", &a[i].id);


        gotoxy(20,9);
        printf("Enter product name : ");
        scanf(" %s", a[i].name);


        gotoxy(20,11);
        printf("Enter product quantity : ");
        scanf(" %d", &a[i].quantity);


        gotoxy(20,13);
        printf("Enter product price : ");
        scanf(" %f", &a[i].price);


        fp = fopen("addproduct.txt","a");
        fprintf(fp, "%d %s %d %f", a[i].id, a[i].name, a[i].quantity, a[i].price); //Without this line. No problem with looping.


        gotoxy(20,17);
        printf("Record saved!\n\n");


        fclose(fp);


        gotoxy(20,19);
        printf("Do you want to enter new product? Y / N : ");






        scanf(" %c", &checker);
        checker = toupper(checker);




        i++;






        system("cls");
    }
    while(checker=='Y');


return(0);
}

Originally Posted by Salem

> int i=0;
> struct product a[i];
You mis-understood what GReaper was saying.

This creates an array of ZERO length.

Simply doing i++ later in the program doesn't make the array any bigger!

Start simple.
struct product a[20];
and make sure your loop exits when you reach 20 entries.

> gotoxy(20,5);
> printf("\xB2\xB2\xB2\xB2\xB2\xB2\xB2\xB2
Here's a tip.
Remove ALL the eye-candy pretty formatting until the rest of the program is FULLY debugged and working.
You'll waste no end of time trying to keep it pretty while you're still trying to get the basics sorted out.

Alright. Thank you for replying.
May I ask, what if I want the input expandable ? More than 20.

I'm trying to let the user enter the data, and exit whenever they want.
Do you have any tips ?

Thank you in advance.

Originally Posted by GReaper

Like I said, "realloc()" should be used for that. It can change the size of a dynamically allocated array.

Your approach as I see it though is to save each entry to a file. That's fine, albeit inefficient, but you have to choose a method. There's no point in allocating all that memory when you need only a single struct variable.

Hi Greaper, can I use this code as an example ?
But, I can see the code need to input N value. Can i just use loop and counter for N value inside

ptr=(struct name*)malloc(n*sizeof(struct name)); ?

Code:

#include<stdio.h>
#include<stdlib.h>
struct name {
   int a;
   char c[30];
};
int main(){
   struct name *ptr;
   int i,n;
   printf("Enter n: ");
   scanf("%d",&n);

/* Allocates the memory for n structures with pointer ptr pointing to the base address. */
   ptr=(struct name*)malloc(n*sizeof(struct name));
   for(i=0;i<n;++i){
       printf("Enter string and integer respectively:\n");
       scanf("%s%d",&(ptr+i)->c,&(ptr+i)->a);
   }
   printf("Displaying Infromation:\n");
   for(i=0;i<n;++i)
       printf("%s\t%d\t\n",(ptr+i)->c,(ptr+i)->a);
   return0;}

Output
Enter n: 2 <------ I need this to be dynamic.
Enter string and integer respectively:
Programming
22
Enter string, integer and floating number respectively:
Structure
33

Displaying Information:
Programming 22
Structure 33