With the two diodes reversed and a 910 Ohm resistor removed, a NOR gate is created. The next step was to build a S-R latch using the NAND gates and inverters, which holds some basic memory.

Texas Instruments’ 5400 and 7400 TTL quad 2-input NAND gate has been in continuous production since 1964 and is the progenitor of what is probably the most numerous breed of integrated circuits ...