Hidden in plain sight: How Dave Staugas got away with hiding a text message inside TOS?

People who worked on TOS are very clever.

Sure, it's very easy to make fun of them. We all know the shortcomings of The Operating System (which is what the acronym stands for, according to a recent Leonard Tramiel interview): allegedly slow, allegedly buggy, gets in the way when you want to write games or demos. We all heard (or said) things like these at some point in our lives.

But, without going into much detail, as someone who's spent quite some time pouring over the TOS source code, I can say that I've been very pleasantly surprised by it. For sure, any programmer who gets seriously close to the ST hardware can pretty much beat TOS in almost every respect in terms of speed. But what people don't realise is that the TOS team had to stuff as much generic functionality as they could (because that's what an Operating System does: it sacrifices speed for reusability and generability), inside a limited amount of space, on an unknown plaform that was being developed as they were programming it, in a very limited amount of time (it was reported that they shipped v1.0 in 6 months).

One person from that team was Dave Staugas. You might recognise him from a humble art package he developed.

But this is not the focus of this article. Instead we're going to talk about this little snippet coming from a hex dump of TOS:

1C 1E 00 00 1E 1E 20 20 44 61 76 65 20 53 74 61             Dave Sta
55 67 61 73 20 6C 6F 76 65 73 20 42 65 61 20 48     Ugas loves Bea H
61 62 6C 69 67 20 4E 75 08 00 00 01 67 2C 3D 79     ablig Nu  
g,=y

I'm sure everyone has heard or seen this hidden message. The question we'll try to answer is: how did he pull it off? Because even back then, if someone tried to hide a message the naive way, it'd get found out by others and then removed.

Let's take this step by step. In assembly language the naive way to include a message like this would be to just include the string, like so:

dc.b "Dave StaUgas loves Bea Hablig"

And just be done with it. But again, this is easily found out by others at any point. A second thing to try would be a bit more sneaky:

dc.b $44, $61, $76, $65, $20, $53, $74, $61, $55, $67, $61, $73, $20, $6C, $6F, $76, $65, $73, $20, $42, $65, $61, $20, $48, $61, $62, $6C, $69, $67, $20

So pretty much just grab the hex values of the message and include those. But, again, this is too easy - especially for people in the 80s who used to be much more hardware about code, this would very easily be discovered by others as being ASCII characters, and be discarded.

This is what Dave did (note: this is wild speculation on my side, but I'm confident that this is pretty much what happened). Firstly, he found a really big file that had gnarly code and probably nobody wanted to touch it in fear of breaking something. The file in question is resposible for printing text in GEM - and if you've seen the capabilities of GEM text printing, you can imagine the complexity. I'll just say that the file is about 2500 lines, which was gigantic for the machines of the time.

 He then jumped around the middle of the file and found a good spot for the code: some tables are there: