Save some bytes

Makefile

@@ -6,7 +6,7 @@ PYTHON = python3
 
 all: ponydos.img
 
-FS_FILES = wallpaper.bin shell.bin
+FS_FILES = bg.bin shell.bin
 
 ponydos.img: ponydos.bin $(FS_FILES)
 	$(PYTHON) assemble_floppy.py $@ ponydos.bin $(FS_FILES)

ponydos.asm

@@ -72,8 +72,8 @@ load_wallpaper:
 	; TODO: error management? Surely this works...
 
 load_shell:
-	mov ax, 0x1000
-	mov es, ax
+	push word 0x1000
+	pop es
 	mov si, shell_name
 	call open_file
 	xor bx, bx
@@ -118,15 +118,20 @@ mainloop:
 draw_wallpaper:
 	pusha
 	push es
+	push ds
 
-	mov bx, 0xb800
-	mov es, bx
+	xor ax, ax
+	mov ds, ax
+
+	push word 0xb800
+	pop es
 
 	mov si, WALLPAPER
 	xor di, di
 	mov cx, 80*25
 	rep movsw
 
+	pop ds
 	pop es
 	popa
 	ret
@@ -135,8 +140,8 @@ flip_mouse_cursor:
 	pusha
 	push es
 
-	mov bx, 0xb800
-	mov es, bx
+	push word 0xb800
+	pop es
 
 	; Column
 	xor bh, bh
@@ -224,7 +229,7 @@ modify_sector:
 	ret
 
 	.error:
-		; Reset the disk system unconditinoally, as we have no
+		; Reset the disk system unconditionally, as we have no
 		; kernel panic handler to go to after 3 tries and proper
 		; error handling would take too much code
 		xor ah, ah
@@ -235,7 +240,7 @@ modify_sector:
 ; Filesystem
 ; ------------------------------------------------------------------
 
-wallpaper_name: db 'wallpaper.bin', 0
+wallpaper_name: db 'bg.bin', 0
 shell_name: db 'shell.bin', 0
 
 ; in: