[code]
#include
#include
WSADATA wsaData;
WORD version;
int error;
version = MAKEWORD( 2, 0 );
error = WSAStartup( version, &wsaData );

if (argc < 2) {
printf("Usage: %s hostname", argv[0]);
exit(-1);
}[/code]

To summarize all those cosmetics changes I would recommend the following:

/* for inet_ntoa() */
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdlib.h>
#include <stdio.h>
int main(int argc, char **argv) {
 if (argc < 2) {
   fprintf(stderr,"Usage: %s hostname\n", argv[0]);
   exit(1);
 }
 struct hostent *hp = gethostbyname(argv[1]);
 if (hp == NULL) {
   fprintf(stderr,"gethostbyname() failed\n");
   exit(1);
 } else {
   printf("%s = ", hp->h_name);
   unsigned int i=0;
   while ( hp -> h_addr_list[i] != NULL) {
     printf( "%s ", inet_ntoa( *( struct in_addr*)( hp -> h_addr_list[i])));
     i++;
   }
   printf("\n");
   exit(0);
 }
}