What powerful operating system was created in 1970s that has now set the industry

Python write an expression that executes the loop body as long as the user enters a non-negative number. note: if the submitted code has an infinite loop, the system will stop running the code after a few seconds and report "program end never reached." the system doesn't print the test case that caused the reported message. sample outputs with inputs: 9 5 2 -1

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In which part of a professional email should you try to be brief, but highly descriptive?