I remember this one. I successfully extracted the data from this disk back in the day, but using a much less complicated method. My memory is a bit hazy after 30 years, but basically it went like this:
Reboot, let it load for a few seconds, then open the disk drive door. It will print "I/O ERROR" and drop to the basic prompt. At this point, the autorun flag is set, but you can clear it by typing "FP". Close the disk drive, then you can load any of the basic programs and list them. If you look through the listings, you will find some CALLs, which switch the RWTS. So I just loaded the files, switched the RWTS, and saved them to a normal disk. Ta-da!
Did you read the whole article? What about the calls from the program itself which check that you are running the modified DOS? Might you be confusing this with another copy protected program?
I was running the modified DOS. Initially I booted the Math Blaster disk and ran from there. Later I realized I could boot normal DOS, and then swap the DOS in memory. I don't recall if I had to mess with zero page. I think those calls did it automatically, but I don't remember.
This also explains why the BASIC programs were obfuscated. Once you find the calls to switch the RWTS, the rest is easy. Getting around the obfuscation wasn't too hard though. I just ran the program and then interrupted it.
I do suspect that I had a different version. The directory listing looks a bit different, and I don't recall so many control characters in the filenames. It's possible that they published an updated version with more obfuscation (although it's also possible that I've just forgotten after so many years).
As as aside, I wasn't primarily interested in reverse-engineering the copy protection when I did this. I was more interested in their graphics drivers. The program had a thing where it would override the standard functions for drawing characters to the screen, so you could use the standard PRINT command and instead of using text mode, it would draw bitmapped characters into the graphics page. I thought it was rather clever.
From the link mentioned in another comment as a more stable and permanent URL: ""Math Blaster" is a 1983 educational game programmed by Richard Eckert and Janice Davidson, Ph.D. and distributed by Davidson & Associates."
Wow. The timing of this post was opportune, because just yesterday I had a chance to see (again) Bob Davidson, the husband of Janice (Jan) Davidson and a leader of Davidson & Associates, at a meet-up of alumni of various Davidson Institute for Talent Development programs for young people. The Math Blaster software was an early example of successful edutainment software, and it led to quite a bit of revenue that funded other software titles developed in-house or acquired over the years by Davidson & Associates.
Jan and Bob Davidson timed the Dot Com boom perfectly in choosing a time to leave active management of Davidson & Associates and begin funding philanthropy, which for them has been most devoted to developing programs for unusually bright young people in the United States. The best-known program of the Davidson Institute is the Davidson Fellows program, which gets in the news at least once a year as new Davidson Fellowship awards are announced, but the biggest program by number of young people involved is the Davidson Young Scholars program, which includes several alumni and I think some current members who are active participants here on Hacker News.
We talk here on Hacker News about some other software entrepreneurs who get in the news a lot these days for their philanthropic efforts, but I thought I should give a shout-out to one of the early adopters of a career change to full-time philanthropy funded by a software fortune, the Davidsons, because their philanthropy has a direct influence on the Hacker News community.
Interestingly, the text itself is modern (at the very least, it mentions a Google Groups URL), but it's still wrapped at 40 columns.
I find that very nostalgic for some reason, and it doesn't seem to hurt readability at all.
Interesting how the app store era (especially in Apple's ecosystem) has made it much more difficult to copy software.
I remember in '80s and '90s copy protection was a major focus (for software companies and legislators alike). As a kid of that era, I remember looking for cracks on Usenet and FidoNet.
More info on Copy Protection here:
Honestly, it's not particularly difficult to copy programs from the app store. With a jailbroken phone, you can just grab an app off the phone's file system.
I think the real difference is the constant, relentless change in platforms presented to mobile phone consumers. Every year, it's a new phone, a major operating system upgrade, or something else disrupting the ecosystem, so that no out-of-band trade in raw files can take root.
When you have a zombie fanbase chasing the latest glitter, and disruptive changes introduced every six months, it's tough to gain traction when you have expend so much energy just to keep up with the herd.
Not to mention that in that era, titles were often US$39, $49 (or more) and in today's dollars that would be much higher. Compare to most apps on the app store that are typically $4.99 or less... certainly makes paying for titles a lot more palatable for the would-be pirate.
... and that today's $4.99 is actually something like $1-$2 in 80's dollars.
There's also the fact that you have to jailbreak it first, which is going to be scary and difficult for many (most) users.
When DRM was only enforced by the software, you just patched over the software and were good to go. Now that it's enforced by the operating system, it no longer appears so simple to the average user.
I'd say copy protection, in the spirit of this particular article, still lives on in the type of copy protection applied to video content provided on optical media.
Walled gardens, and the like, are really about server side retention of discrete copies, requiring a user to stream content by means of a continuous connection, or loading content onto a trusted (locked) system that the end user cannot (or rather, should not) directly control.
They're different models of control, but both have been around for a while.
With a walled garden model, you're visiting a restaurant and the food comes to you already prepared.
With copy-protected content, you can buy and keep as many packets of instant food, and mix with water whenever you want, but you're prevented from understanding how to formulate the mix yourself from raw precursor ingredients, although no one can stop you from trying.
This is a level of dedication I fear we lost somewhere in the 90s. That, or being a cracker teaches you more about how computers work than most jobs.
I especially love where the author likens resuming a crack attempt after giving up for months to a detective picking up a cold case.