##### Interactive

In the interactive mode of operation, the NeXtMidas shell is explicitly entered (after nmstart is run) with the operating system command

    > nm

Commands are then entered in response to the `nM>` shell prompt. Any command not recognized by NeXtMidas is automatically passed on to the operating system for possible execution there.

There are several advantages to interactive mode that are lost when one-shot commands are executed by an ephemeral NeXtMidas shell:

Command Recall - A durable NeXtMidas shell remembers the commands it executed and provides both history listing services and shortcuts for retrieving, modifying, and re-executing previous commands.

Parameter Prompting - When the NeXtMidas shell receives an interactive command that ends with a single '?' character, it fetches parameter names and default values from the command's dictionary entry and prompts the user for any missing parameters.

Result Table Durability - The NeXtMidas shell maintains a table of calculated data values that can be referred to by name on command lines. The result table only exists during an interactive session.

Concurrent Command Execution and Communication - In a piped macro, commands execute concurrently and communicate with each via messages passed through the shell.

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