.orig x3000

LD R6, CONVTO
LEA R0, PROMPT
PUTS

GETC
OUT
LD R1, SUB_NUM_ONES_3200
JSRR R1
LD R0, NEWLINE
OUT

LEA R0, RESULT
PUTS
ADD R0, R4, #0
OUT
LEA R0, RESULT_2
PUTS
ADD R0, R2, R6
OUT
LD R0, NEWLINE
OUT

HALT
;---------------
; Local data
;---------------
SUB_NUM_ONES_3200   .FILL x3200
PROMPT      .STRINGZ "Enter a single character: "
RESULT      .STRINGZ "The number of 1's in '"
RESULT_2    .STRINGZ "' is: "
NEWLINE     .FILL   '\n'
CONVTO      .FILL #48
;------------
; Subroutine
;------------
.ORIG x3200
;-------------------------
; Subroutine Instructions
;-------------------------
ST R7, BACKUP_R7_3200
LD R1, DEC_0
LD R2, DEC_0
LD R3, COUNTER

ADD R1, R0, #0
ADD R4, R0, #0

ZERO_OR_ONE
  ADD R1, R1, #0
  BRzp ZERO
  BRn ONE

ZERO
  ADD R1, R1, R1
  ADD R3, R3, #-1
  BRz FINISH
  BRp ZERO_OR_ONE

ONE
  ADD R1, R1, R1
  ADD R2, R2, #1
  ADD R3, R3, #-1
  BRz FINISH
  BRp ZERO_OR_ONE

FINISH
  LD R7, BACKUP_R7_3200

  RET
;-----------------
; Subroutine data
;-----------------
BACKUP_R7_3200      .BLKW #1
DEC_0           .FILL #0
COUNTER         .FILL #16

.end