Writing a mere string out to a file on a non-UNIX was nowhere near as easy as ‘fd = open (“a file”, O_WRONLY); write (fd, p_aString, strlen (p_aString)); close (fd);’ on UNIX. Many systems required either a block-oriented or a fixed-record (with the record structure to be defined first) to be opened, the block or the record to be written out and then the file to be closed. Your record-oriented file has grown very large? Brace yourself for a coffee break after you invoke the “file close” system call on it. Did you process get killed off or just died mid-way through? Well, your file might have been left open and would have to be forcefully closed by your system administrator, if you could find one. Your string was shorter than the block size, and now you want to append another string? Read the entire block in, locate the end of the string, append a new one and write the entire block back. Wash, rinse and repeat. Oh, quite a few systems out there wouldn’t allow one to open a file for reading and writing simultaneously.
Flawed make? Try to compile a 100 file project using JCL or DEC’s IND using a few lines of compilation instructions. Good luck if you want to have expandable variables, chances are there wouldn’t be any supported. You want to re-compile a kernel? Forget about it, you have to “generate it” from the vendor supplied object files after answering 500+ configuration related questions and then waiting for a day or two for a new “system image” (no, there were no kernels back then outside UNIX) to get linked.
Awkward UNIX shell? Compared to crimes a numbers of vendors out there committed, even JCL was the pinnacle of “CLI” design.
No matter how perfect or imperfect some things were in UNIX back then, hordes of people ended up running away screaming from their proprietary systems to flock to UNIX because suddenly they could exchange the source code with their friends and colleagues who could compile it and run within minutes, even if some changes were required. Oh, they could also exchange and run shell scripts someone else wrote etc. In the meantime, life on other planets was difficult.
That was well before I met AS/400 and MVS.
And then I had contact with a Burroughs A-series and it's appropriately named OS, MCP.
OTOH, I love the 3270s.