1. Write a LC-3 subroutine for printing “Hello” for N times. Write a main program to input N from the keyboard, call the subroutine and then output “Hello” for N times.

Here is the LC-3 subroutine for printing "Hello" for N times:

; Subroutine to print "Hello" for N times
; Input: R0 = N (number of times to print)
; Output: None

HELLO_SUB:
    LD R1, HELLO_STR  ; Load address of "Hello" string
    AND R0, R0, #0   ; Clear R0
    ADD R0, R0, #10  ; Set R0 to 10
LOOP:
    BRz END_LOOP     ; If R0 is zero, exit loop
    ADD R0, R0, #-1  ; Decrement R0
    TRAP x22         ; Output "Hello"
    ADD R6, R6, #-1  ; Decrement stack pointer
    ST R1, R6, #0    ; Save address of "Hello" string on stack
    BRnzp LOOP       ; Continue looping
END_LOOP:
    RET              ; Return from subroutine

; String "Hello"
HELLO_STR .STRINGZ "Hello"

And here is the main program to input N from the keyboard, call the subroutine, and output "Hello" for N times:

; Main program to call HELLO_SUB and output "Hello" for N times

.ORIG x3000

; Prompt user for N
LEA R0, PROMPT_N
PUTS
GETC
OUT
IN
PUTS

; Convert input to decimal
LD R1, ASCII_ZERO
ADD R2, R0, #-10 ; Subtract 10 to convert from ASCII
ADD R2, R2, R1
ADD R0, R2, #0

; Call HELLO_SUB
JSR HELLO_SUB

; Output "Hello" for N times
LOOP:
    LD R1, HELLO_STR
    TRAP x22
    ADD R0, R0, #-1
    BRnzp LOOP

; String "Enter N: "
PROMPT_N .STRINGZ "Enter N: "

; ASCII value of zero
ASCII_ZERO .FILL x0030

.END

The program prompts the user to enter N, converts the input from ASCII to decimal, calls HELLO_SUB, and then outputs "Hello" for N times.