c pointer understanding issue

Question

Please have a look at the following code and tell me where does ***ptr locates ? i.e. i have a feelings that ***ptr actually locates at ptr[0][0][0] Am I wrong ? The following is a 3d representation of pointer. where I am trying to assign some characters and later i wanted to test what is the index of ***ptr? will be waiting

#include<stdio.h>
#include<conio.h>
#define row 5
#define rw 3
#define col 10


char ***ptr;
int i,j,k;


void main()
{

clrscr();

ptr=(char *)malloc(row*sizeof(char *));

for(i=0;i<row;i++)
    {
        *(ptr+row)=(char *)malloc(rw*sizeof(char *));
        printf("\t:\n");

           for(j=0;j<rw;j++)
           {
           *(*(ptr+row)+rw)=(char *)malloc(col*sizeof(char *));
           if(i==0 && j==0)
               {       //   *(*(ptr+row)+rw)="kabul";
            **ptr="zzz";

               }
           else
            *(*(ptr+row)+rw)="abul";
           printf("\taddress=%d %d%d = %s\n",((ptr+row)+rw),i,j,*(*(ptr+row)+rw));

           }

         printf("\n");
    }


printf("%c %d",***ptr,ptr);
getch();
}

Answer 1

First of all, I find your coding style extremely hard to read.

Answering your question, yes, ptr[0][0][0] is a synonym of ***ptr. Thats because a[b] is by definition equal to *(a+b), so ptr[0] is equal to *ptr, etc.

Said that, here is my version of your code:

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#define row 5
#define rw 3
#define col 10


char ***ptr;

int main()
{
    int i, j;

    ptr = (char***)malloc(row * sizeof(char **));

    for(i = 0; i < row; i++)
    {
        ptr[i]= (char**)malloc(rw * sizeof(char *));
        printf("\t:\n");

        for(j = 0; j < rw; j++)
        {
            ptr[i][j] = (char*)malloc(col * sizeof(char));
            if (i == 0 && j == 0)
            {
                strcpy(ptr[i][j], "zzz");
            }
            else
            {
                strcpy(ptr[i][j], "abul");
            }
            printf("\taddress=%p %d,%d = %s\n", ptr[i][j], i, j, ptr[i][j]);

        }
        printf("\n");
    }
    return;
}

Note the following changes:

• Never write void main in C or C++. And throw away any book that prints it.
• The argument of malloc is usually the number of elements times the size of the element. Place special attention to the real type that you intend to use.
• The return of malloc is usually cast to the type pointer-to-the-type-of-the-element.
• The index in the arrays should be i and j, not row and rw.
• Why all the *(ptr + x) stuff? That's why we have the ptr[x] syntax.
• You probably want to use strcpy to fill your strings, but difficult to say without explaining the problem.
• When you want to printf a pointer, use %p.
• If you use malloc, include <stdlib.h>.
• Prefer local variables (i, j) to global ones, particularly for loops.
• And a few other minor changes here and there...

PS. <conio.h>? Really? Are you still using Turbo-C or what?