diff --git a/STATUS.md b/STATUS.md
index 952a0e9e..73bd6300 100644
--- a/STATUS.md
+++ b/STATUS.md
@@ -204,7 +204,7 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$B794`   | `convert_u8_A_to_FAC1` | DONE     |                                                    |
 | `$B7B5`   | `STRVAL`               | PARTIAL  | Only for 38k memory model                          |
 | `$B7F7`   | `convert_FAC1_to_ADDR` | NOT DONE |                                                    |
-| `$B849`   | `add_HALF_FAC1`        | DONE     |                                                    |
+| `$B849`   | `add_HALF_FAC1`        | DONE     | From the Microsoft BASIC, original name: FADDH     |
 | `$B850`   | `sub_MEM_FAC1`         | DONE     |                                                    |
 | `$B853`   | `sub_FAC2_FAC1`        | DONE     |                                                    |
 | `$B862`   | `add_align_exponents`  | DONE     |                                                    |
diff --git a/src/basic/math/b849.add_HALF_FAC1.s b/src/basic/math/b849.add_HALF_FAC1.s
index adb72fe7..e9fca350 100644
--- a/src/basic/math/b849.add_HALF_FAC1.s
+++ b/src/basic/math/b849.add_HALF_FAC1.s
@@ -3,15 +3,19 @@
 ;; #LAYOUT# *   BASIC_0 #TAKE
 ;; #LAYOUT# *   *       #IGNORE
 
-;
+; This file is under the MIT license, it contains code released by Microsoft Corporation.
+; See LICENSE for more information.
+
 ; Math package - add 0.5 to FAC1
 ;
+; This is verified to be identical to the original Microsoft implementation where it was named FADDH.
+;
 ; See also:
 ; - [CM64] Computes Mapping the Commodore 64 - page 112
 
 add_HALF_FAC1:
 
-	ldy #>const_HALF
 	lda #<const_HALF
+	ldy #>const_HALF
 
 	jmp add_MEM_FAC1
diff --git a/tools/similarity.c b/tools/similarity.c
index d608e378..c0360de4 100644
--- a/tools/similarity.c
+++ b/tools/similarity.c
@@ -22,7 +22,11 @@ int phase_mask[MAX_SIZE+MAX_SIZE];
 
 #define NUM_CHUNKS 1
 // Pairs of start, end memory addresses of known exact similarity with the open source Microsoft BASIC
-unsigned short microsoft_basic_chunks[NUM_CHUNKS * 2] = {0xBBFC, 0xBC1A};
+unsigned short microsoft_basic_chunks[NUM_CHUNKS * 2] = {
+    0xB849, 0xB84F,
+    0xBBFC, 0xBC1A
+};
+
 
 
 int main(int argc,char **argv)