Why are there both TMP and TEMP environment variables, and which one is right?

Raymond Chen April 17, 2015 Apr 17, 2015 04/17/15

If you snoop around your environment variables, you may notice that there are two variables that propose to specify the location of temporary files. There is one called TMP and another called TEMP. Why two? And if they disagree, then who's right? Rewind to 1973. The operating system common on microcomputers was CP/M. The CP/M operating system...