Problem $4$

An LC$-3$ assembly language program is given below. Carefully read the program and answer the questions that follow. Adding comments will help in partial credit. Label Assembly language instruction

START LDIR$1,$ KBSR

BRzp START

LDI R$0,$ KBDR

LOOP LDI R$1,$ DSR

BRzp LOOP

STI$0,$ DDR

HALT

KBSR $.$FILL xFE$00$

KBDR $.$FILL xFE$02$

DDS $.$FILL xFE$04$

DDR $.$FILL xFE$06$

$.$END

a$.$ What does this program do$?$

b$.$ What is the purpose of the KBSR and KBDR$?$