Why Windows has both TMP and TEMP environment variables: A history of parallel evolution
By
Raymond Chen
An everything bagel for the brain. Substantive, layered, well-seasoned.
Summary
This article explores the historical reason why Windows (and earlier systems) have both TMP and TEMP environment variables pointing to temporary file locations. It traces back to the CP/M operating system from 1973, which had no environment variables, and explains how different operating systems and software ecosystems evolved in parallel — some adopting TMP, others TEMP. The article explains that both exist due to legacy compatibility and that modern Windows treats them as equivalent, with neither being more "right" than the other.
Key quotes
· 3 pulledIf you snoop around your environment variables, you may notice that there are two variables that propose to specify the location of temporary files.
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.
Since it had no environment variables, there was consequently neither a TMP nor a
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