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Trainers - or hacking into a game...

PostPosted: Mon Mar 19, 2012 8:57 pm
by Harvey
I'm no programmer - so hacking a game, for me is hit and miss.

I thought I would have a go at it, anyway - and I wrote an article in Page 6 magazine about this, and was semi-successful with a lot of trial and error.
Something that was done quite often, was to use LDA to set the number of lives to say 5? or whatever.
This could be done on the disk file of the game - but you never knew exactly where it was? Usually it may be near the beginning - making it easier to find.
Because it was just a diskcopy - it does not matter if the game crashed. Sooner or later you could find the exact byte that controlled the lives - if you were
lucky and the programmer used LDA for this..
Some games were so impossibly hard - that without cheating you couldn't get that far at all. eg. Kissin' Kousins and Shamus on the Atari 800.

A quicker way to narrow it down, is to change several LDA's with different values - and if the lives changed - you would know where exactly it was. Crashing the game would happen frequently this way.

This was the only way I could finish Necromancer - adding a lot of lives to the game.

Re: Trainers - or hacking into a game...

PostPosted: Tue Mar 20, 2012 6:49 pm
by Harvey
Of course, when looking at a disk sector - you don't actually see "LDA" there - it's token (representation) is A9 - and from memory? It is something like - A9 00 03, where it is setting up 3 lives for the game start. Of course, there are other possible ways of setting the lives counter, without using LDA to do so. This technique works also for 68000 computers, but you would look for FC 00 03, or was it, FC 00 00 03 instead... With the Atari 800, I could look at a source listing published in ANALOG Computing - and change the lives for one of their arcade games published with the magazine. Anyway - I somehow did this by my own detective work, and on my own... Andrew did take note of how easy it can be to hack into a game to make it easier - and I think he made sure that Hawkquest, could not be hacked into so easily that way... That he set up the lives count differently.