INT 21,F - Open a File Using FCB

AH = 0F

DS:DX = pointer to unopened ~FCB~

on return:

AL = 00 if file opened

= FF if unable to open

- opens an existing file using a previously setup FCB

- the FCB fields drive identifier, filename and extension

must be filled in before call

- sets default FCB fields; current block number is set to 0;

record size is set to 80h; file size, date and time are set

to the values from the directory

- does not create file, see ~INT 21,16~

- DOS 2.x allows opening of subdirectories, DOS 3.x does not