$6\mathrm{.}12$

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 x$0$A$)$ and then outputs the same line.