Date   : Mon, 14 May 2001 16:46:42 +0100
From   : "Richard Gellman" <r.gellman@...>
Subject: Re: Loading locked files

>
>Quoting Thomas Harte (t.harte@...):
>
>> I noticed that some games (Millionaire from Incentive, Karate Combat from
>> Superior) use an OSFILE command to load a locked file. How come this is
>> allowed?
>
>I don't specifically remember how those two games did it, but I seem to
>recall that this was usually achieved by installing an interrupt-driven
>routine which over-wrote the locked bit when the header was read into
>memory, so the OS would see the file as locked if the loader program wasn't
>run first.
>
>James

I think it's far simpler than that.

According to my BBC Master 128 Reference Manual part 1 (Page H.3-7 if any1's
interested), OSFILE only has two functions with the tape filing system
anyway, *SAVE (A=0) and *LOAD (A=255). I would think *LOAD just checks on
the locked bit after loading, and denies any further action if set.

-- Richard Gellman