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Core Dump

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Core Dump - Work In Progress

Episode 45

October 9, 1997 : Blade Lords CD-Rom edition

Document the features of your games!

A few years ago, when I'd finished a game, I threw away most of the notes I had made. Nowadays I try to keep everything. I have this huge filing system with all the notes concerning my games.

But that does not mean that I don't lose stuff. Such as "how did I code the Blade Lords copy-protection?" and the (very important...) "Blade Lords source files". Both things were lost.

Blade Lords: MCCM CD-ROM edition

And now I wanted to remove the copy-protection. Ok. I knew how the file system worked (directory in sector 1; 3 bytes per file; every file has a unique number) but that wasn't enough. I just couldn't find the sector checks.

Five hours later I'd found them. Not by some clever trick, but just because I recognised a coding trick I sometimes use for protections (ADD HL,BC; ADD HL,BC; JP (HL)). It works like this: by jumping to an address that is the result of some computation, hackers cannot be really sure where the jump will lead to. Because the computation can be a difficult one. Also, even if they find the address of some suspicious sector-read, they cannot be sure where the routine is being called from (Searches on "CALL routine" or "JP routine" will yield no results as the address is the result of a computation).
To make it even safer, I used a system that locks if the sector-read routine is blocked (e.g. because some hacker put a "RET" instruction in front). Anyway, it was proven that it is indeed an ingenious system, because even I had to scratch my head to crack it, and I coded the damn thing!

As I had now removed the protection, I made a DOS-2 compatible version that can be installed on Harddisk. Also, I removed the bug in world 1-10 (where bonusses appeared in the wall) and I put a little platform in 2-9. Goody.

I will postpone the release of this MCCM CD-rom edition until I know something more about the release date of that MCCM.

Core Dump

With Core Dump, I've got this huge stack of notes. But still most of it is in my head. I would have to take more time to document everything, and although this is my honest intention, it never happens.

But, e.g. the scroll routine (including sprite routines) is quite well documented. As are the main routines. But the overall layout of everything changes all the time, and is scattered over 30 pages or something.

Obsession with pictures?

I also received a very interesting E-mail last week. Because nothing is sure yet, I can't reveal the details. But there is a good possibility... thirst-priority!!!

As Winnie-the-Pooh says:

"...for I am a Bear of Very Little Brain, and long words Bother me."

Go on...

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