[net.micro.cpm] writing w/o opening

ciaraldi@Rochester.ARPA (01/24/84)

From:  Mike Ciaraldi <ciaraldi@Rochester.ARPA>

Under MP/M, there is a checksum in the FCB.
This gets set when you open the file, and you cannot
read or write on the file unless this checksum is correct.
So, the problem of wiping out your directory by not
opening the file first should not occur.

I don't know if this technique is used in newer products
such as CP/M-86 or CP/M-Plus

Mike Ciaraldi
ciaraldi@rochester

POURNE%mit-mc@sri-unix.UUCP (02/16/84)

From:  Jerry E. Pournelle <POURNE@mit-mc>

it's not. sigh
    Date: 24 Jan 84 15:06:00 EST (Tue)
    From: Mike Ciaraldi <ciaraldi at Rochester.ARPA>
    To:   Info-Cpm at brl-vgr.ARPA, w8sdz at brl.ARPA
    Re:   writing w/o opening

    Under MP/M, there is a checksum in the FCB.
    This gets set when you open the file, and you cannot
    read or write on the file unless this checksum is correct.
    So, the problem of wiping out your directory by not
    opening the file first should not occur.

    I don't know if this technique is used in newer products
    such as CP/M-86 or CP/M-Plus

    Mike Ciaraldi
    ciaraldi@rochester