One interesting thing that caught my eye was this:
> Hardware bugs also happened, through component or engineering failure; TX-2 was, after all, an experimental computer. The quickest way to get a bug fixed was to write a very simple program that failed in spite of obvious correctness, and the easiest way to “explain” this bug to the hardware engineers was to show them a Polaroid photograph of the panel of toggle switches that “stored” 24 words of 38 bits each and the console lights. Leaving a program in toggle switch memory that should obviously work, but failed, was a sure way to get the hardware people to fix a bug.
I checked out a memorandum on the toggle switch storage system (http://www.bitsavers.org/pdf/mit/tx-2/6M-5661_Toggle_Switch_...). From what I understand, it allowed direct manual input of data and instructions into memory through these switches. TX-2 had 24 registers, each 37 bits long. Sixteen of these could be manipulated using the toggle switches on the main control panel. So, programmers could directly alter instructions.
The system involved some kind of resistor-switch matrix (not sure exactly what it does though!). But it enabled switches to toggle between 0 (ground position) and 1 (connected to some kind of resistor driver) - this, in turn, would help represent individual bits. Neat stuff!
If anyone has fun stories related to all this, I'd love to hear them!