graphics: preventing cursorxy(32,80) from scrolling the screen

assets/bios/quick.js

@@ -0,0 +1,32 @@
+
+// probe bootable device
+
+var _BIOS = {};
+
+// Syntax: [Port, Drive-number]
+// Port #0-3: Serial port 1-4
+//      #4+ : Left for future extension
+// Drive-number always starts at 1
+_BIOS.FIRST_BOOTABLE_PORT = [0,1]; // ah screw it
+
+Object.freeze(_BIOS);
+
+///////////////////////////////////////////////////////////////////////////////
+
+// load a bootsector using 'LOADBOOT'
+let portNumber = 0;
+let driveStatus = 0;
+while (portNumber < 4) {
+    if (com.areYouThere(portNumber)) {
+        com.sendMessage(portNumber, "LOADBOOT");
+        driveStatus = com.getStatusCode(portNumber);
+        if (driveStatus == 0) break;
+    }
+    portNumber += 1;
+}
+if (portNumber < 4) {
+    eval(com.fetchResponse(portNumber).trimNull());
+}
+else {
+    printerrln("No bootable medium found.");
+}