El velador es un sistema? justifique

What are "open-loop" and "closed-loop" systems

Write a program that asks the user to enter the name of an input file. if the file does not exist, the program should prompt the user to enter the file name again. if the user types quit in any uppercase/lowercase combinations, then the program should exit without any further output.

Alison is having a hard time at work because hee inbox is flooded with emails every day. some of these emails are unsolicited. some of other she don’t need. which action should she take to better manager her emails?