While digging through some old IBM technical reports, I ran into something that didn’t quite fit the usual pattern. Buried between dry charts and assembler notes were these odd references to an “experimental modular assembler.” At first, I figured it was just another obscure internal tool — IBM had tons of those back then. But the more I read, the stranger it got. The fragments kept pointing toward something bigger, almost like a forgotten programming language. After weeks of connecting dots across journals, archives, and even some old interviews, I think I’ve stumbled across traces of CAL — Combined Assembly Language, a short-lived hybrid that seems to have existed between 1959 and 1964.

From what I’ve pieced together, CAL was a mix of raw assembly and higher-level constructs. Imagine writing assembly but with IF...ENDIF, FOR...ENDFOR, even modules and macros baked in — stuff that wouldn’t become mainstream until years later. The idea was that you’d write CAL, run it through a translator to turn it into assembly, and then feed that into the normal assembler. In other words: early attempts to bridge the brutal low-level control of assembly with the readability of structured programming.

Here’s a reconstructed example based on notes I found:

MODULE CalculatePi DECLARE Pi VALUE 3.14159 BEGIN FOR Count FROM 1 TO 100 IF Count > 50 PRINT Count, Pi * Count ENDIF ENDFOR END ENDMODULE

What makes this even wilder is the trail of evidence. A 1965 IBM Systems Journal article talks about “an experimental modular assembler allowing intermixed macros and structured operators.” No mention of CAL by name, but it lines up almost perfectly. The underground Black Programming Guide from the 1970s (a kind of hackerish student handbook floating around MIT and Stanford) mentions programmers using a “CAL method” with a nonstandard translator. Then, in 2018, while digitizing Carnegie Mellon’s archives, a box labeled ADC Seminar 1963 turned up — inside were handwritten notes with MODULE/ENDMODULE directives, stamped Algorithm Development Consortium — C.A.L. And if that’s not enough, in a 2001 interview for an IBM retirees’ magazine, engineer David L. Siemen casually recalled: “We experimented with what we called a combined assembler… but it was too avant-garde for the hardware of the time.”

So why did CAL vanish? Probably because it was too weird and too far ahead. Programmers were either deep in pure assembly or moving to Fortran, and IBM itself didn’t back CAL officially. By the time people were ready for structured programming, COBOL and ALGOL were already stealing the show.

Still, I think CAL matters. Even if it never went beyond prototypes and seminar notes, it shows that the urge to mix low-level control with high-level structure was alive way earlier than most of us realize. CAL might have been a dead end — or maybe it was just a few decades too early.

Now I’m wondering: has anyone else ever run into CAL, or other “ghost languages” that only survive in scraps, rumors, or forgotten manuals?