Question : what is hosts and bootptab file in HP-UX?

how are /etc/hosts and /etc/bootptab files in HP-UX different from each other? we use bootptab file in order for computer on our LAN to connect to the internet?
we add entries to the bootptab file in order for pc's on our LAN to connect to internet. what is hosts file use for then?

Answer : what is hosts and bootptab file in HP-UX?

bootp is obsolete protocol for configuring network parameters of ethernet machines.

Install random Linux distribution, like one from Mandriva or anything recent called BSD and it will run bootp's modern day replacement called ISC DHCPD.
There you have one config file to replace whatever bootptab did and add a bit more.

Make sure you teach DHCPD to update DNS records, so you do not have to use hosts file any more.

bootptab takes capability database file:

hostname:option=value:
 :option=value:
...
 :option=value

hostname:
...

Capabilities are these:
     bf   Bootfile
     bs   Bootfile size in 512-octet blocks
     cs   Cookie server address list
     df   Merit dump file
     dn   Domain name
     ds   Domain name server address list
     ef   Extension file
     gw   Gateway address list
     ha   Host hardware address
     hd   Bootfile home directory
     hn   Send client's hostname to client
     ht   Host hardware type (see Assigned Numbers RFC)
     im   Impress server address list
     ip   Host IP address
     lg   Log server address list
     lp   LPR server address list
     ns   IEN-116 name server address list
     nt   NTP (time) Server (RFC 1129)
     ra   Reply address override
     rl   Resource location protocol server address list
     rp   Root path to mount as root
     sa   TFTP server address client should use
     sm   Host subnet mask
     sw   Swap server address
     tc   Table continuation (points to similar "template" host entry)
     td   TFTP root directory used by "secure" TFTP servers
     to   Time offset in seconds from UTC
     ts   Time server address list
     vm   Vendor magic cookie selector
     yd   YP (NIS) domain name
     ys   YP (NIS) server address
(above is taken form FreeBSD manual pages)

dhcp can offer many more options.