Since we're dealing with fiction, from a Deepness in the Sky:
>The Qeng Ho's computer and timekeeping systems feature the advent of "programmer archaeologists":[1] the Qeng Ho are packrats of computer programs and systems, retaining them over millennia, even as far back to the era of Unix programs (as implied by one passage mentioning that the fundamental time-keeping system is the Unix epoch):
>>Take the Traders' method of timekeeping. The frame corrections were incredibly complex - and down at the very bottom of it was a little program that ran a counter. Second by second, the Qeng Ho counted from the instant that a human had first set foot on Old Earth's moon. But if you looked at it still more closely ... the starting instant was actually about fifteen million seconds later, the 0-second of one of Humankind's first computer operating systems.
>This massive accumulation of data implies that almost any useful program one could want already exists in the Qeng Ho fleet library, hence the need for computer archaeologists to dig up needed programs, work around their peculiarities and bugs, and assemble them into useful constructs.
So to answer your question, a mess of standards going back millennia with glue-code everywhere. I blame the separation of documentation and code for the coming dark age.
One of the many interesting things about the Zones of Thought is that all of those problems with software you describe are explicitly there to protect the likes of humans from what can exist on the other side of the singularity.
Since we're dealing with fiction, from a Deepness in the Sky:
>The Qeng Ho's computer and timekeeping systems feature the advent of "programmer archaeologists":[1] the Qeng Ho are packrats of computer programs and systems, retaining them over millennia, even as far back to the era of Unix programs (as implied by one passage mentioning that the fundamental time-keeping system is the Unix epoch):
>>Take the Traders' method of timekeeping. The frame corrections were incredibly complex - and down at the very bottom of it was a little program that ran a counter. Second by second, the Qeng Ho counted from the instant that a human had first set foot on Old Earth's moon. But if you looked at it still more closely ... the starting instant was actually about fifteen million seconds later, the 0-second of one of Humankind's first computer operating systems.
>This massive accumulation of data implies that almost any useful program one could want already exists in the Qeng Ho fleet library, hence the need for computer archaeologists to dig up needed programs, work around their peculiarities and bugs, and assemble them into useful constructs.
So to answer your question, a mess of standards going back millennia with glue-code everywhere. I blame the separation of documentation and code for the coming dark age.