This paper describes a virtual system that emulates an ARM-based processor machine, created to replace a traditional hardware-based system for teaching assembly language. The virtual system proposed here integrates, in a single environment, all the development tools necessary to deliver introductory or advanced courses on modern assembly language programming. The virtual system runs a Linux operating system in either a graphical or console mode on a Windows or Linux host machine. Student feedback indicates that teaching with the virtual system has become progressively easier, clearer and more interesting while keeping staff support to a minimum. Since no software licenses or extra hardware are required to use the virtual system, students are able to carry their own ARM emulator with them on a USB memory stick. Institutions adopting this, or a similar, virtual system can also benefit by reducing the capital investment in hardware-based development kits, and by enabling distance-learning courses.