Re: Emacs history, and "Is Emacs difficult to learn?"

[Óscar Fuentes]

Rustom Mody <rustompmody@gmail.com> writes:

> b. If you are saying jumping into the middle of an instruction can be
> useful, well I confess this is beyond my ken. For one I believe that
> in assembly alone with arithmetic on the location-counter that should
> be possible. On the other hand I dont know how to do that without
> getting into undefined instruction issues.

When I was a kid with a Sinclair ZX Spectrum, I found that cracking
videogames was more fun than playing them. One common obfuscation
technique consisted on prefixing chunks of instructions with bytes that
confused the disassembler.

But one day confronted a self-decryption method that processed the
game's binary, then jumped into itself but at a "wrong" instruction
offset, which had the effect of executing a very different sequence of
instructions that performed another decrypting round with a different
method.

The show of byte-mingling capability and the displayed mastery on Z80
machine code was truly impressive, but in the end it was fairly easy to
crack, albeit quite a bit boring after the first impression waned.