Thread: Dereferncing Void Pointer

Hi, so that I could understand void pointers I created the following program:

Code:

#include <stdio.h>
#include <string.h>

int main(void) {

    char word[] = "Zero";
    int number = 0;
    void *ptr = NULL;

    printf("number = %d\t[%p]\n",number,&number);
    printf("word   = %s\t[%p]\n",word,&word);

    /* Point to number. */
    ptr = &number;

    printf("*ptr   = %d\t[%p]\n",*((int *)ptr),(int *)ptr);

    /* Modify value of number. */
    *((int *)ptr) = 1;


    /* Point to word. */
    ptr = &word;

    printf("*ptr   = %s\t[%p]\n",(char **)ptr,(char *)ptr);

    /* Modify value of product */
    strcpy(ptr,"One");

    printf("number = %d\t[%p]\n",number,&number);
    printf("word   = %s\t[%p]\n",word,&word);

    return 0;

}

The program works fine, however i really want to fully understand what is going on with the deferencing of the void pointer, for example:

With the following code:

Code:

    ptr = &number; 
    *((int *)ptr) = 1;

Why can't you just do:

Code:

    ptr = &number;    
    *(int *)ptr = 1;

And again with this code, (i'm guessing it's becuase its a pointer to a pointer?):

Code:

    ptr = &word;
    strcpy(ptr,"One");

Could someone please explain why this is neccessary or if you can point me at
an explaination I would be most grateful for any assistace.

Thanks
~P

Hi, it was the additional brackets that I had issue with, earlier in the program, I had compilation errors without them, clearly I must have done something wrong.

Thanks for your assistance.

~P