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's an example LC-3 subroutine and main program that will print "Hello" for N times:

; Subroutine to print "Hello" for N times
;
; Input: R0 contains the number of times to print "Hello"
; Output: None

    .ORIG x3000

PRINT_LOOP:
    LD R1, HELLO_STRING   ; Load address of "Hello" string into R1
    LD R2, ASCII_NEWLINE  ; Load newline character into R2
    ADD R0, R0, #-1       ; Decrement N
    BRz PRINT_EXIT        ; If N = 0, exit the loop
    PUTS                 ; Print "Hello"
    ADD R0, R0, #-1       ; Decrement N again
    BRz PRINT_EXIT        ; If N = 0, exit the loop
    OUT                  ; Print newline
    BRnzp PRINT_LOOP      ; Loop back to start

PRINT_EXIT:
    RET                  ; Return from subroutine

; Data section
;
; Define the "Hello" string and newline character in ASCII

HELLO_STRING .STRINGZ "Hello"
ASCII_NEWLINE .FILL x0A

    .END

; Main program to input N and call the subroutine
;
; Input: None
; Output: None

    .ORIG x4000

MAIN:
    LEA R0, N             ; Load address of N into R0
    IN                  ; Read N from keyboard
    JSR PRINT_HELLO      ; Call subroutine to print "Hello" for N times
    HALT                 ; Halt the program

; Subroutine to print "Hello" for N times
;
; Input: R0 contains the number of times to print "Hello"
; Output: None

PRINT_HELLO:
    ST R0, SAVE_R0       ; Save R0 on the stack
    JSR PRINT_LOOP       ; Call the "Hello" printing loop
    LD R0, SAVE_R0       ; Restore R0 from the stack
    RET                  ; Return from subroutine

; Data section
;
; Define the input variable N and a temporary storage location

N .BLKW 1
SAVE_R0 .BLKW 1

    .END

To run this program:

1. Assemble the code using LC-3 assembler.
2. Load the resulting .obj file into the LC-3 simulator.
3. Run the program and enter a value for N when prompted.
4. The program will print "Hello" for N times.