This binary file holds the last received BIDs. The number of records of this
file is defined in the INIT.SRV file. This file is very important and must
not be edited or changed otherwise the list of the messages could be lost.
This file can only be opened for reading.

 It is organized with records, each record containing information on a BID.
This is a circular file and the first record of the file contains the pointer
of the last overwritten record in the msg_number field. Never modify this
file while the BBS is running.

 Structure of one record (C language) :

typedef struct {

  char  mode         ;  /* 1   Type of message (A,B,P,T)       */
  char  fbid[13]     ;  /* 13  BID of the message              */
  long  msg_number   ;  /* 4   Number of the message           */

} bidfwd             ;  /* 18  bytes = length of one record    */

In C language, all strings are ended with a NULL (00 hex) character.