Thread: Pointer to pointer question

What is the difference between

Code:

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

int dothings(char **k){
 printf("%c",*k);
}

int main(){
  char* c='h';
  dothings(&c);
}

and

Code:

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

int dothings(char *k){
 printf("%c",*k);
}

int main(){
  char* c='h';
  dothings(&c);
}

The output is the same,but i dont understand why.Can you provide an example where the first occasion would be usefull.Thanks

In C, all parameters are passed by copying. To create a pass by reference, we use pointers or & (address of) operators - because an address, and a copy of that address, have exactly the same value. That is to say, whether I give you the note saying get the mail from mailbox 123, or I make a copy of that note with the mailbox address of 123, the net result is the same. You know to go to mailbox 123, either way.