Difference between select and poll

/*
@file name : poll.c
@brief: poll for data in to stdin
*/

#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/poll.h>

#define MAX 100
#define TO_MS(val) (val*1000)

int main()
{
        char      line[MAX];
        int       ret;
        struct pollfd   fd[1];

        while(1)
        {

                fd[0].fd = 0;
                fd[0].events = POLLIN | POLLPRI | POLLERR | POLLHUP | POLLNVAL ;

                ret = poll(fd,1,TO_MS(6));
                printf("poll ret[%d]\n",ret);
                if ( ret > 0 && fd[0].revents)
                {
                        printf("event occur\n");
                }
                if(ret < 0 )
                {
                        printf("error [#%d,%s]\n",errno,strerror(errno));
                        return -1;
                }
                if(ret == 0)
                {
                        printf("time out\n");
                        return 0;
                }
                fgets(line,MAX,stdin);
                printf("%s",line);
        }
        return 0;
}



/*
@file name : select.c
@brief: select for data in to stdin
*/


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

#include <sys/select.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>


#define MAX 100
#define TO_MS(val) (val*1000)

int main()
{
        char      line[MAX];
        int       ret,fd=0;
        fd_set readfds;
        struct timeval timeout;

        while(1)
        {
                /* set the time out */
                timeout.tv_sec = 2;
                timeout.tv_usec = 0 ;

                /* initialize the fd set*/
                FD_ZERO(&readfds);

                /*set the action to the fd - here stdin*/
                FD_SET(0, &readfds);


                ret = select(fd + 1, &readfds, NULL, NULL, &timeout);
                if (ret == 0)
                {
                  /* timed out, return */
                        printf("Time out happend.!!\n");
                        break ;
                }
                else if (ret < 0)
                {
                        /* there is an error, return */
                        printf("Error Occurs Err[#%d,%s]\n",errno,strerror(errno));
                        break ;
                }
                else
                {
                        if (FD_ISSET (0, &readfds))
                        {
                            printf("data in to read\n");
                        }
                        else
                        {
                          printf("Strange..!! No Data available after fd set\n");
                          continue;
                        }
                }

                fgets(line,MAX,stdin);
                printf("%s",line);
        }

      return 0;
}