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by zabzonk4 hours ago |
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upvoteby fooqux4 hours ago|
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"Rewind to 1973. The operating system common on microcomputers was CP/M. The CP/M operating system had no environment variables. That sounds like a strange place to start a discussion of environment variables, but it’s actually important."
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upvoteby flohofwoe4 hours ago|
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Just a few lines below:

"Over time, programs were written with MS-DOS as their primary target, and they started to realize that they could use environment variables as a way to store configuration data. In the ensuing chaos of the marketplace, two environment variables emerged as the front-runners for specifying where temporary files should go: TEMP and TMP."

And before that there are a few paragraphs describing the migration of applications from i8080/Z80 based CP/M towards x86 based DOS via mechanical translation.

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upvoteby Delk2 hours ago|
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Sounds like the short answer is "because there was no standard for the variable set by MS-DOS from the get go".

The background is that the issue hadn't existed in CP/M because there hadn't been environment variables. Perhaps if the issue had already been seen in CP/M, the developers of MS-DOS might have defined a standard variable to avoid it. Maybe. Other than that it doesn't seem to have much to do with CP/M specifically.

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upvoteby rendaw4 hours ago|
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I was curious seeing this thread, and I just looked and don't get it either. AFAICT the CP/M references could have been entirely omitted and nothing in the narrative about TMP and TEMP would change.
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upvoteby jodrellblank3 hours ago|
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Except that DOS was made to have its first programs ported from CP/M, so it’s relevant to explain that there were no environment variables to inherit from CP/M and no developer habits or program standards to inherit from CP/M programs.
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upvoteby drfloyd513 hours ago|
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Which is irrelevant to TMP or TEMP.

It could simply be: When envars were added to MSDOS…

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upvoteby jodrellblank3 hours ago|
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Multics had envars in the 1960s and Unix in the 1970s, why were they ‘added’ to DOS when it was so close to an older OS, why didn’t it inherit them from CP/M? Did it get TMP from CP/M and introduce TEMP because computers were bigger but then?
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upvoteby elch55 minutes ago|
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Did Multics actually have something really similar to the much later envars introduced in Unix?
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upvoteby imtringued1 hours ago|
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Those questions appear awfully overfit to the current blog post.
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upvoteby jodrellblank2 minutes ago|
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That comment feels awfully cherry-picked to the perfect untestable rebuttal based on what you want to be true.

How did you measure the fitness and decide it was 'over'?

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