- [[Terminal]] ## General - outermost layer of & interface to the [[Operating Systems|Operating System]] - the shell is a command interpreter that exposes the user to an interface that works with the underlying [[Operating Systems]] - allows you to execute operations using text/commands - more efficient than [[GUI]] (Graphical User Interface) - REPL stands for - READ - read command - EVAL - evaluate/run command - PRINT - output result of EVAL - LOOP - repeat https://www.ibm.com/docs/en/aix/7.2?topic=administration-operating-system-shells