Type Cast

[ram619]

Could anyone please tell me whats happenning in line number 10 and 12. The output of this code is 2 and 0.

#include<stdio.h>
#include<conio.h>

void main()
{
 int arr[3]={2,3,4};
 char *p;
 clrscr();
 p=arr;
 p=(char*)((int*)(p));
 printf("%d\n",*p);
 p=(int*)(p+1);
 printf("%d",*p);
 getch();
}

[DeanMSands3]

Well, look at what's happening to your pointer and it'll let you know.
I modified your code to do this.

#include<stdio.h>
#include<conio.h>

void main()
{
 int arr[3]={2,3,4};
 char *p;
 //clrscr();
 p=arr;
 printf("*p:%d, p: %ld\n",*p, p);
 p=(char*)((int*)(p));
 printf("*p:%d, p: %ld\n",*p, p);
 p=(int*)(p+1);
 printf("*p:%d, p: %ld\n",*p, p);
 //getch();
}

It gave me this.

*p:2, p: 2293552
*p:2, p: 2293552
*p:0, p: 2293553

Let's take it one step further.

#include<stdio.h>
#include<conio.h>

void main()
{
 int arr[3]={2,3,4};
 char *p;
 //Int size is 4 on 32-bit so cast arr as char* before adding.
 char *end=((char*)arr)+sizeof(arr);  for(p=(char*)arr;p<end;p++){
  printf("*p:%d, p: %ld\n",*p, p);
 }
 //getch();
}

Which, on a little-endian 32-bit system yields:

*p:2, p: 2293548
*p:0, p: 2293549
*p:0, p: 2293550
*p:0, p: 2293551
*p:3, p: 2293552
*p:0, p: 2293553
*p:0, p: 2293554
*p:0, p: 2293555
*p:4, p: 2293556
*p:0, p: 2293557
*p:0, p: 2293558
*p:0, p: 2293559

(Notice that the pointer shifted from 2293552 to 2293548. This is unimportant except to know that there are differences between the two programs.)

Hopefully, this is clear as mud and just as tasty.

Happy coding!

[ram619]

DeanMSands3.....Thanks a Lot...........