Make output code work also on the original IBM PC

bootsect.asm

@@ -67,6 +67,29 @@ _start:
 	; Save bootdrive
 	mov [drivenumber], dl
 
+select_os:
+	mov si, prompt
+	.print:
+		lodsb
+		test al, al
+		jz .end
+		; On the original IBM PC BIOS the int 0x10 will clobber this
+		mov ah, 0xe
+		int 0x10
+		jmp .print
+	.end:
+
+	xor ax, ax
+	int 0x16
+
+	cmp al, 'e'
+	jne calc_constants
+
+	mov si, ettinos_kernel_name
+	mov di, kernel_name
+	mov cx, 11
+	rep movsb
+
 calc_constants:
 	; Disk organization:
 	; Reserved sectors (MBR)
@@ -310,9 +333,9 @@ chs:
 	pop ax
 	ret
 
-%include "hexprint.inc"
-
+prompt: db "Select OS. 'e' for EttinOS, any other key Nor86.", 0
 kernel_name: db "KERNEL  BIN"
+ettinos_kernel_name: db "SYSTEM  BIN"
 
 times 510-($-$$) db 0
 db 0x55, 0xaa