Going from old to new:
You might learn techinques to be conservative with memory usage or execution times, but then again on systems with gigabytes of RAM and fast, multiple cores where you will want to do a threaded application most of that is redudant or not applicable.
Going from new to old:
Some of the algorithm and data structure concepts will apply even to 8-bit stuff, though the programming languages and methods will be different from what today is state of the trade. The newer Atari stuff you're getting into, the more alike modern tools it will become.
If you're thinking from a career perspective, a very small amount of people today get hired and can make a living on programming games for older systems while many do it on their spare time and sometimes even get commercially published, though usually not making a load of money from that. If you have had a dream about making your own programs, you might as well want to try it if time permits.
I'm a bit confused what a career application developer is though. Have you been working with smartphone apps, though not the core programming but rather the functional and UI design of those? Google fails to explain this term to me. Or have you been working with developing career application forms, like a curriculum vitae expert?
Edited by carlsson, Thu Oct 12, 2017 1:04 AM.