From 7a37b76d10976c935c4bbfaec5da52260999d43d Mon Sep 17 00:00:00 2001
From: Rikard Nordgren <hrn@posteo.net>
Date: Mon, 30 Mar 2026 21:19:15 +0200
Subject: [PATCH] Add mov_RES_FAC1 (MOVFR)

---
 STATUS.md                              |  1 +
 src/aliases/,aliases_ram_lowmem.s      |  2 +-
 src/basic/math_mov/bb8f.mov_RES_FAC1.s | 24 ++++++++++++++++++++++++
 tools/similarity.c                     |  2 +-
 4 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 src/basic/math_mov/bb8f.mov_RES_FAC1.s

diff --git a/STATUS.md b/STATUS.md
index 71f5293c..c251fc18 100644
--- a/STATUS.md
+++ b/STATUS.md
@@ -227,6 +227,7 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$BAFE`   | `div10_FAC1_p`         | DONE     |                                                    |
 | `$BB0F`   | `div_MEM_FAC1`         | DONE     |                                                    |
 | `$BB12`   | `div_FAC2_FAC1`        | DONE     |                                                    |
+| `$BB8F`   | `mov_RES_FAC1`         | DONE     | From the Microsoft BASIC, original name: MOVFR     |
 | `$BBA2`   | `mov_MEM_FAC1`         | DONE     | From the Microsoft BASIC, original name: MOVFM     |
 | `$BBA6`   | `get_FAC1_via_INDEX`   | DONE     | From the Microsoft BASIC, no label                 |
 | `$BBC7`   | `mov_r_FAC1_TMP2`      | DONE     | From the Microsoft BASIC, original name: MOV2F     |
diff --git a/src/aliases/,aliases_ram_lowmem.s b/src/aliases/,aliases_ram_lowmem.s
index dbd6664e..571ee14d 100644
--- a/src/aliases/,aliases_ram_lowmem.s
+++ b/src/aliases/,aliases_ram_lowmem.s
@@ -33,7 +33,7 @@
 	!addr TEMPST    = $19 ; $19-$21  temporary string stack descriptors
 	!addr INDEX     = $22 ; $22-$23  INDEX1 vector
 	!addr INDEX2    = $24 ; $24-$25  INDEX2 vector
-	!addr RESHO     = $26 ; $26-$2A  temporary variables, [!] our usage might be different
+	!addr RESHO     = $26 ; $26-$2A  floating point result
 	!addr TXTTAB    = $2B ; $2B-$2C  start of BASIC code
 	!addr VARTAB    = $2D ; $2D-$2E  end of BASIC code, start of variables
 	!addr ARYTAB    = $2F ; $2F-$30  pointer to start of array storage
diff --git a/src/basic/math_mov/bb8f.mov_RES_FAC1.s b/src/basic/math_mov/bb8f.mov_RES_FAC1.s
new file mode 100644
index 00000000..9a8624e2
--- /dev/null
+++ b/src/basic/math_mov/bb8f.mov_RES_FAC1.s
@@ -0,0 +1,24 @@
+;; #LAYOUT# STD *       #TAKE
+;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
+;; #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 - Copy RES to FAC1
+;
+; This is verified to be identical to the original Microsoft implementation where it was named MOVFR.
+;
+
+
+mov_RES_FAC1:
+    lda RESHO
+    sta FAC1_mantissa
+    lda RESHO+1
+    sta FAC1_mantissa+1
+    lda RESHO+2
+    sta FAC1_mantissa+2
+    lda RESHO+3
+    sta FAC1_mantissa+3
+    jmp normal_FAC1
diff --git a/tools/similarity.c b/tools/similarity.c
index d8ec935b..bd3067cc 100644
--- a/tools/similarity.c
+++ b/tools/similarity.c
@@ -28,7 +28,7 @@ unsigned short microsoft_basic_chunks[NUM_CHUNKS * 2] = {
     0xB849, 0xB97D,
     0xB983, 0xB9BB,
     0xBA8C, 0xBAB6,
-    0xBBA2, 0xBC1A,
+    0xBB8F, 0xBC1A,
     0xBC2B, 0xBCF2,
 };