diff --git a/src/SUDOKU.MID b/src/SUDOKU.MID
index 1512bff..f8ed85c 100644
--- a/src/SUDOKU.MID
+++ b/src/SUDOKU.MID
@@ -15,21 +15,31 @@ PDL:    BLOCK PDLLEN                   ;Reserve the stack memory
 BPTR==440700                           ;Define a byte pointer.
 
 CHTTYO==1                              ;Define a channel for TTY output.
+CHTTYI==2                              ;Define a channel for TTY input.
 
 START:  MOVE  P,[-PDLLEN,,PDL-1]       ;Initialize the stack.
         .OPEN CHTTYO,[.UAO,,'TTY]      ;Open an output channel on the TTY.
          .LOSE %LSFIL                  ;Gobble up any errors.
         MOVE  A,[BPTR,,HELLO]          ;Load A with a byte pointer to HELLO.
-        PUSHJ  P,OUTSTR                ;Print the out string.
+        PUSHJ  P,PUTLN                 ;Print the out string.
         JRST  DONE                     ;Jump to the end of the program.
+
+;Subroutine to print a string of text on the output.
+; Clobbers A and B.
 OUTSTR: HRLI  A,BPTR                   ;Ensure, A is a byte pointer.
 OUT:    ILDB  B,A                      ;Load the next byte from A.
         JUMPE B,OUTEX                  ;Exit the routine, if all bytes are done.
         .IOT  CHTTYO,B                 ;Print a character.
         JRST  OUT                      ;Jump back to print the next character.
-OUTEX:  .IOT  CHTTYO,[^M]              ;Print carriage return and
-        .IOT  CHTTYO,[^J]              ;newline characters.
-        POPJ  P,                       ;Return from the subroutine.
+OUTEX:  POPJ  P,                       ;Return from the output routine.
+
+;Subroutine to print an entire line of text, including a line break.
+;Clobbers A and B.
+PUTLN:  PUSHJ P,OUTSTR                 ;Calls the OUTSTR subroutine
+        .IOT  CHTTYO,[^M]              ;Print a carriage return
+        .IOT  CHTTYO,[^J]              ;and a new line
+        POPJ  P,                       ;before returning.
+
 DONE:   .LOGOUT  2,                    ;Exit point for the program.
 HELLO:  ASCIZ  /HELLO WORLD/           ;Define example string.  
 END     START