12/07/2014

C pointer variable

What is the difference between int* n and int *n

If int *n, that is a fallacy that there are 2 type of variables. In fact, variable is a place holder of data only, the variant is the type of data it holds.

int is data structure of 4 bytes while int* is the one of 8 bytes (for 64 bit system).


#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netdb.h>
#include <netinet/in.h>
#include <errno.h>
#include <string.h>

int main(int argc, char* argv[]){
 int fd = socket(AF_INET, SOCK_DGRAM, 0);
 unsigned int zero = 300;
 
 // building address structure 
 struct in_addr* ipaddr = malloc(sizeof(struct in_addr));
 if(ipaddr == NULL){
  perror(strerror(errno));
 }

 zero = *((unsigned int*)ipaddr);
 printf("size of struct in_addr*: %d\n", sizeof(struct in_addr*));
 printf("size of int*: %d\n",sizeof(int*));
 printf("%x\n",zero);
 printf("ipaddr = %x",*((int*)(ipaddr)));
 
 return 0;
}

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