vault backup: 2022-08-01 10:30:55

content/notes/6809.md

@@ -54,7 +54,7 @@ message:
 	.byte "HELLO WORLD", 0
 
 START:
-	ldy #message                                 ; load 
+	ldy #message                                 ; load "message", into the y register
 	bsr puts                                     ; branch to the "puts" subroutine
 	rts                                          ; return
 
@@ -67,14 +67,14 @@ PUTS:
 	pshs a,x,y        ; save a, x, and y          ; store the contents of the a, x, and y registers so they are not overwritten
 	ldx #screen       ; start of screen           ; load the hex value of the memory location of the screen ($0400) into the x register
 more: 
-	lda 0,y+          ; current char -> A         ; load 
+	lda 0,y+          ; current char -> A         ; load the contents of the Y register into the A register and increment Y by one
-	cmpa #$00         ; was it a zero? 
+	cmpa #$00         ; was it a zero?            ; if the character loaded into A was a zero set the equal flag
-	beq done          ; if it was 0 then return 
+	beq done          ; if it was 0 then return   ; if the equal flag is set, branch to the "done" subroutine
-	sta 0,x+          ; write 
+	sta 0,x+          ; write                     ; otherwise, store the contents of the A register into memory at the location (hex value) defined in the X register, and increment the hex value stored in the X register
-	bra more          ; repeat 
+	bra more          ; repeat                    ; branch to the "more" subroutine as there are more character to write
 done: 
-	puls a,x,y        ; restore a, x, y 
+	puls a,x,y        ; restore a, x, y           ; re load the stored values of the a, x, and y registers that were saved earlier
-	rts               ; return from this routine
+	rts               ; return from this routine  
 ```
 
 # Hello World