$6\mathrm{.}12$ a$.$ Write an LC$-3$ machine language routine that echoes the last

character typed at the keyboard. If the user types an $R,$ the program

then immediately outputs an $R$ on the screen.

b$.$ Expand the routine from part a such that it echoes a line at a time. For

example, if the user types:

The quick brown fox jumps over the lazy dog.

then the program waits for the user to press the Enter key $($the ASCII

code for which is $x0A)$ and then outputs the same line.