Lit. Buffer overruns 1719

CP-M. You're correct.

Though I believe Kildall actually got it from the system he used to develop CP-M, the name of which I can't recall right now.

Yes, though on most system they were logical rather than physical sectors.

Prior to CP-M 3.x, the minimum the system could resolve a file size to was 128 bytes. A sector. Even after 3.x came along, a lot of programs didn't support the ability to process the exact resolution byte so, functionally, we all kept using the old method along with the new one.

Correct again. If you needed the length of a text file, you'd open it, get the length, read in the last "sector" then scan it looking for Control-Z.

I recall hearing several explainations for this at the time. One was that there was a need to be able to store NULs in the file. One of the more convincing ones I recall was that the ^Z was chosen because it was the last alpha control key (^A, ^B, ... ^Y, ^Z) and thus was supposed to be a mnemonic for "last character" in the file. With some of the very earliest tools, you actually typed in that ^Z to terminate the file. And if you were doing command line to file creation of a .SUB file, for example, the only way to terminate the input was with an explicit ^Z.

- Bill