If you aren’t old enough to remember when computers had front panels, as [Patrick Jackson] found out after he built a replica Altair 8800, their operation can be a bit inscrutable. After figuring it out he made a pair of videos showing the basics, and then progressing to a program to add two numbers.
Even when the Altair was new, the days of front panels were numbered. Cheap terminals were on their way and MITS soon released a “turnkey” system that didn’t have a front panel. But anyone who had used a minicomputer from the late 1960s or early 1970s really thought you needed a front panel.
You may never program an Altair by the front panel, but it is still an interesting glimpse into what computing looked like only a few decades ago. While you might think that the front panel was a mere curiosity, it was not unusual to have to key in a bootloader program manually so you could then load other software — often a better bootloader — from paper or magnetic tape. Some computers even had the early bootloader code printed on the front panel for reference.
A front panel can also help you debug programs and hardware problems since you are probably looking right at the bus in a real computer. Of course, with an emulator, the emulator is just driving the front panel for make-believe, but it still works the same way.
We did our own front panel tutorial for the PDP/8. The operation is similar, but not exactly the same. The front panel for the BLUE computer was especially fun because it used the limited lights and switches available to the FPGA board it lived on. You can see it in a video in this post about the real-world implementation of a fake educational computer.