I also remember the first version of Smalltalk from Digitalk that was character based and windowed. It was called Methods. I can’t seem to find any reference to it on the web now.
"Methods, our character-based Smalltalk, is now available for $79- It has all of the features of Smalltalk/V except graphics, rules, source-level debugger, and object-swapping. However, it supports color, includes the communication package, and does not require a mouse."
I'm not sure if it qualifies as mixing logical levels but I once tracked down a printer bug where the PDF failed to print.
The culprit was an embedded TrueType font that had what (I think) was a strange but valid glyph name with a double forward slash instead of the typical single (IIRC whatever generated the PDF just named the glyphs after characters so /a, /b and then naturally // for slash). Either way it worked fine in most viewers and printers.
The larger scale production printer on the other hand, like many, converted to postscript in the processor as one of its steps. A // is for an immediately evaluated name in postscript so when it came through unchanged, parsing this crashed the printer.
So we have a font, in a PDF, which got turned into Postscript, by software, on a certain machine which presumably advertised printing PDF but does it by converting to PS behind the scenes.
A lot of layers there and different people working on their own piece of the puzzle should have been 'encapsulated' from the others but it leaked.
security with cryptography is mostly about logical level problems, where each key or operation forms a layer or box. treating these as discrete states or things is also an abstraction over a seqential folding and mixing process.
debugging a service over a network has the whole stack as logical layers.
most product management is solving technical problems at a higher level of abstraction.
a sequence diagram can be a multi-layered abstraction rotated 90 degrees, etc.
As an “enterprise” developer in the 80’s, we all had beepers to go along with our suits and ties. People often thought we must be doctors, but we were just corporate mainframe developers.
I worked for a few banks starting in the 1980’s. It was all MVS. End user applications were created using CICS and IMS. What we used to call OLTP (online transaction processing).
