Using Mars. Develop a command processor using modules from earlier assignments as outlined below.

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Develop and test a simple command processor for MARS that will support at least $3$ commands:

"help":

display the list of commands supported by your command processor and a few words describing each command, it's parameters $($if any$),$ and function.

"echo"

display the text following the command

"exit"

shut down the command processor.

Use the following functions from previous assignments and demos:

String copy demo $($Module $04$ Demo$),$

String parse procedure Assignment $($Assignment $04),$

String compare assignment $($Midterm I Project$),$

String read and write assignment using memory mapped I$/$O $($Assignment $06).$

$($Do not use syscall I$/$O$)$

Consistent with typical command processors your main program should:

prompt the user for a command $($something like $">")$

read the command line entered by the user at the keyboard

echo the command line entered by the user to the display

parse the first "token" to find the command name

using the string compare code in a previous assignment find the correct entry point in a table of commands and entry points

if the command is not found in the table write an error message and loop

execute the command passing the input line as a parameter $($be sure to follow system register saving and parameter passing conventions$)$

repeat this process until the user enters the "exit" command.

You may implement additional commands for extra credit of $10$ to $20$ points.$$ Submit your extra credit proposal to Lou via email for comment$/$approval prior to implementation.