Virtualisation is used to run operating systems which use the same hardware as the real computer on which the software is running, but if you want to run an old operating system that used completely different hardware, you need an emulator. Here we'll show you how to emulate the classic BBC Micro.
Emulation is often used to bring old computers (and games consoles) back to life. If you’ve been using computers for longer than you care to remember, this could be a trip down memory lane. Alternatively emulation provides a means of learning about the early days of computing.
Unlike virtualisation packages which allow to you run any compatible operating system, emulators tend to recreate either a single machine and its operating system or, perhaps, a family of computers. Because emulation involves translating every single processor instruction it’s an inherently slow method but, given that it’s used to recreate old and hence slow computers, it’s more than fast enough on modern hardware.
In the main, you’ll be using emulation, as opposed to virtualisation, to run programs for computers that are no longer available. For example, you can emulate the venerable BBC Micro which was produced by Acorn for use in education. It was also extremely popular as a home computer back in the early 80s which was when the home computer revolution was just taking off.
The emulator we’re using is BeebEm which you can download for the Mac from www.g7jjf.com/beebemmac.htm. This software emulates the BBC Micro's hardware including its 6502 processor. It also includes the ROM-based software which was roughly equivalent to both a PC’s BIOS and its operating system, since the BBC Micro could be used without a disk drive. Technically, the inclusion of this software is illegal but, in reality, we’d have to question whether the copyright holder would really be interested in enforcing their rights on 30-year-old software.
David Bradforth contributed to this article.
1. Run BeebEm and a window will appear showing the BBC Micro’s start up page with 80s style chunky white lettering on a black background. The introductory text shows that the BBC Micro had 32KB of memory (that's about 256,000 times less than a PC with 8GB of RAM) and that it was running the BASIC programming language.
2. The > symbol is the same as the command prompt you'll find even in Windows 8 today. Start by entering and running a very simple BASIC program which was common way of using home computers in the 80s. Type ‘10 FOR N=1 TO 10’ (without the quotation marks) followed by the Enter key on the first line, ‘20 PRINT “HELLO WORLD” ‘ on the second, and ‘30 NEXT N’ on the third. Now to execute the program, type ‘RUN’.
3. Now load a program from the BBC Micro’s emulated floppy disk drive disk which, in reality, is a Windows file. BeebEm comes with several such disk images. Select ‘Run Disc’ from BeebEm’s File menu, select games.ssd and click on Open. To prove that the BBC Micro genuinely did have a colour display, a colour menu will be displayed giving you the option of four different games.
4. To appreciate something of the sophistication of 80s gaming, enter 4 to experience the wonders of Cylon Attack. After this quick introduction, if you want to learn more about the BBC Micro, which truly was a ground breaking machine in its day, we suggest that you do so with reference to the BBC Micro’s original user manual that you can download from here.