@@ -1,53 +0,0 @@ 
-.include "devices.xyw"
-
-; ;ain program: calculate and print factorial of 5
-$5 fact JSRw 
-print8 JSRw
-$0A terminal.output STB
-end JMPw
-
-; Factorial subroutine
-; a8 -- | [xy]
-.label fact
-  ; Save argument to both registers
-  POPxy
-  .label fact.loop 
-    PSHy $0 EQU fact.end0 JCNw
-    PSHy $1 EQU fact.end1 JCNw
-    ; Decrement y and multiply
-    DECy PSHx PSHy MULx POPx
-    fact.loop JMPw
-  .label fact.end0
-    ; Edge case: factorial of 0 is 1
-    $1
-    CLRxy
-    RTS
-  .label fact.end1
-    ; Return result
-    PSHx
-    CLRxy
-    RTS
-
-; Printing subroutine
-; a8 -- | [xy]
-.label print8
-  POPx 
-  ; If value is less than 10, print single digit
-  PSHx $A LTH print8.single JCNw
-  ; Divide by 10: stack becomes [remainder, quotient]
-  PSHx $A DIV
-  ; Save remainder to y for later
-  SWP POPy
-  ; Call print8 recursively with quotient (still on stack)
-  print8 JSRw
-  ; Print the saved remainder
-  PSHy $30 ADD terminal.output STB
-  CLRxy
-  RTS
-  .label print8.single
-    ; Print single digit
-    PSHx $30 ADD terminal.output STB 
-    CLRx
-    RTS
-
-.label end

@@ -0,0 +1,35 @@ 
+.include "devices.xyw"
+
+; Main program: calculate and print factorial of 7
+$00 $07 fact JSRw 
+print16 JSRw
+$0A terminal.output STB
+end JMPw
+
+; Factorial subroutine
+; a16 -- | [xy]
+.label fact
+  ; Save argument to both registers
+  POPxyw
+  .label fact.loop 
+    ; Need to work with 16-bit comparisons
+    ; but JCN only works with 8-bit values, so remove high byte first
+    PSHyw $00 $00 EQUw SWP POP fact.end0 JCNw
+    PSHyw $00 $01 EQUw SWP POP fact.end1 JCNw
+    ; Decrement y and multiply
+    DECyw PSHxw PSHyw MULxw POPxw
+    fact.loop JMPw
+  .label fact.end0
+    ; Edge case: factorial of 0 is 1
+    $1
+    CLRxyw
+    RTS
+  .label fact.end1
+    ; Return result
+    PSHxw
+    CLRxyw
+    RTS
+
+.include "print16.xyw"
+
+.label end

@@ -1,6 +1,6 @@ 
 .include "devices.xyw"
 
-; ;ain program: calculate and print factorial of 5
+; Main program: calculate and print factorial of 5
 $5 fact JSRw 
 print8 JSRw
 $0A terminal.output STB

@@ -20,5 +20,3 @@ ; Print single digit (need low byte of XW since value is 0-9)
     PSHxw SWP POP $30 ADD terminal.output STB
     CLRxw
     RTS
-
-.label end

@@ -8,6 +8,7 @@ "run_test d6.xyw assert_output_in_range 1 6"
   "run_test on-error.xyw assert_output_equals \$'Error: Division by zero.\\nError: Unknown error.\\n'"
   "run_test print-args.xyw test1 test2 -- assert_output_equals \$'print-args.xim, test1, test2\\n'"
   "run_test factorial8.xyw assert_output_equals \$'120\\n'"
+  "run_test factorial16.xyw assert_output_equals \$'5040\\n'"
 )
 
 ### Helper functions