[dljsjr]

Caml 1.0 was released in '85 and OCaml (the O is for Object Orientation) was 1996. Multithreading wasn't a high priority for anybody back then. The JVM didn't even have threads until 1997 and those threads were green threads, OS threads came to Java later.

[pasc1878]

However this is all Unix and academia based. If you wrote code for Windows and OS/2 in the commercial world you were using threads sine '89 and thus did not want to use the languages that did not use threads e.g. python, OCaml

[cmrdporcupine]

In the late 80s and early 90s we wrote things with threads but they were primarily a kind of convenience to get multitasking behaviour and not any kind of performance boost.

Multicore / multiprocessor systems were not a mainstream thing in consumer hardware until the 21st century.

[int_19h]

It would be pretty difficult to write threaded code for Windows in 1989, since it didn't support threads until WinNT 3.1 (1993).

But even in late 90s it was still common for desktop Win9x apps to use the main window message loop for async processing (Win32 API itself heavily encouraged it at the time - e.g. that's how OS timers work) in lieu of threads.

[jeltz]

That was much later, in the mid 90s. But who did have threads in the mid 80s was Erlang which back then only existed in Ericsson's research lab. Ericsson had anpther internal language which Erlang drev inspiration from which also had support for concurrency.