4 bit calculator built using individual transistors

A 4-bit calculator is built using different types of logic gates for each full adder. It is able to add up to 31. The inputs and outputs are shown by lighting up LEDs.

The first full adder is built with integrated circuits that consist of XOR gates, AND gates, and OR gates. Next, the second full adder is built with individual transistors using the same logic gates as full adder 1. The third full adder is built with all NAND gates. Finally, the fourth full adder is built with all NOR gates.

Each input is changed by moving a dip switch up or down on the breadboard. The full adders have a sum bit and carry out bit. The sum bit lights up an LED while the carry out bit is sent as an input into the next full adder. In the last full adder the carry out lights an LED when it is in the on state.