INT 21,22 - Random Write Using FCB

AH = 22h

DS:DX = far pointer to an opened ~FCB~

on return:

AL = 00 if write successful

= 01 if diskette full or read only

= 02 if ~DTA~ is too small

- write records to random location in file opened with FCB

- FCB must be setup with drive id, filename, extension,

record position and record length before call

- current record position field in FCB is not updated