Duncan Bayne

Binary Half Adder in The Incredible Machine

I’m sure most geeks my age remember The Incredible Machine. I’ve been playing this (and other) old DOS games using DOSBox, relaxing during this long weekend.

Then it occurred to me … I bet I can build a binary half-adder using TIM.

Three and a half hours later, success! A bit of Googling also turned up an alternative implementation, as well as a full adder implemented using lasers in TIM2.

You can see my TIM binary half-adder here. I demonstrate adding 0+0, 0+1, 1+0, and finally 1+1.

The trick to doing the 1+1 addition is the XOR gate consisting of two bellows and a balloon between them. The way it works is that if either bellows is pushed, the balloon moves and the light is triggered. If both are pushed, the balloon stays in the centre and the light stays dark. Obviously, if neither bellows are pushed the balloon also stays in the centre.

Geek joy!