A Shareware Timelock

 BBS: Inland Empire Archive
Date: 04-11-92 (11:30)             Number: 132
From: RICHARD VANNOY               Refer#: 122
  To: JIM TANNER                    Recvd: NO  
Subj: A Shareware Timelock           Conf: (2) Quik_Bas
JT>OK... so how do you know when/where a "blind spot" exists.?

First you have to know how long the BIO.SYS file is.  That
can be obtained from reading the directory file size.
Next you need to know how many 512 byte sectors are in a
cluster (usually 1, 2 or 4).  I don't know how to do this
in QB, but it is available through an interrupt call.

So, suppose BIO.SYS is 23,456 bytes and the cluster size is
2 sectors or 1024 bytes.

Divide 23,456 by 1024 = 22.90
So the file takes 23 full clusters (since the next file to
be written MUST go at the start of the NEXT cluster).

So  23 * 1024 = 23,552
minus file size 23,456
              =     96

So there are 96 bytes "invisible" to DOS, at the end of
cluster 23.

Note that I have never done this.  I am presuming from my
knowledge of DOS and common sense and my limited knowledge
of DOS interrupts that writing to those bytes is possible.
If I'm correct, then I've done the easy part, the theory.
Next would come learning enough to write the code.
(Translation:  I'm just thinking out loud, so don't come
hollering to me if you try some of this stuff and it
trashes your hard disk!  <grin>)

> MegaMail 2.1b #0:Support FREE software!  Write it yourself!

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