The Locked Door

I still remember the first time I came across the symbol of a NAND gate in my notes. A simple curve, a line, and a tiny circle at the end. At first glance, it seemed ordinary, almost insignificant compared to the more “logical”

AND, OR, and NOT gates that carried obvious meaning. AND felt like cooperation, OR felt like choice, NOT felt like
rebellion. But NAND? It was simply an AND gate that had been flipped upside down. A contradiction born out of

the most straightforward operation.

Back then, it looked like nothing more than a locked door, an unnecessary twist in an already strict world of 0s and 1s. Yet, as I dug deeper into the heart of digital logic, I realized that this locked door was, in fact, a master key.

The paradox fascinated me: the gate that seemed most restrictive, most redundant, turned out to be the most

powerful of them all. With only NAND, I could recreate every other gate, every circuit, every processor, every

system that fuels the devices we live with today. It was like discovering that a single note on a piano, when

repeated and arranged, could compose an infinite symphony And in that paradox, I found not just logic,

but life itself.

The Paradox Unfolds – NAND in Action

It all begins with a small paradox: a single gate that seems too simple to matter, yet powerful enough to build

everything: the NAND gate. At first glance, its truth table looks ordinary, just an AND followed by a negation:

Nothing special, right? But hidden in this table is a strange power. Feed the same input into both sides, and

something unexpected happens:

From sameness, we create opposition. Out of redundancy, a NOT gate is born.
With NOT in hand, the puzzle deepens. Use NAND again, and the AND gate, seemingly destroyed at first, rebuilds

itself:

A paradox inside a paradox: NAND cancels AND, only to resurrect it. And through De Morgan’s laws, OR follows:

Once NOT, AND, and OR are possible, all of digital logic unfolds. Every arithmetic circuit, every processor core, every instruction your computer executes, rebuilt from this single outsider gate.

From Denial to Memory: The Cross-Coupled Latch

At first sight, NAND is just a gate of refusal:

But when two NANDs are cross-coupled, their outputs loop into each other. What emerges is no longer simple

rejection… it is memory. This circuit, called the SR Latch, responds to inputs S (Set) and R (Reset):

A Set forces Q to 1. A Reset forces Q to 0. And when left alone, the circuit remembers its previous state. Two gate

that reject togetherness suddenly embody persistence. They give digital systems the power to remember past

inputs, a cornerstone of computation. Every flipflop, every register, every clocked sequence in your processor

descends from this humble latch.

The Keeper of the World: NAND Flash Memory

Zoom out further, and the paradox only grows. The storage in your phone or laptop relies on NAND, not as a gate, but as NAND flash memory. At its heart lies the floating-gate MOSFET: a transistor that can trap or release
electrons on an insulated gate, shifting its threshold voltage. This allows information to be stored as charge:

• Program (write): electrons pushed onto the floating gate.
• Erase: electrons removed.
• Read: current flow is sensed, revealing “0” or “1.”

Billions of these cells are chained into NAND arrays, packing extraordinary density into tiny chips. NAND was

chosen over NOR not for speed, but for its efficiency, higher density, and lower cost per bit. That is why NAND

flash dominates SSDs, USB drives, smartphones, and cloud servers.

Think of the paradox here: the gate whose name means “not-and” has become the medium that holds the

affirmations of our digital lives, our photos, our documents, our systems, our collective memory.

Projection – From Logic to Life

We live in a world full of limitations. Resources run out, time runs short, and paths often look blocked. At first

glance, these constraints feel like dead ends, much like NAND once seemed like nothing more than a restricted

AND. But in reality, they are the same kind of hidden universality. Limitations often force us to create, to

reimagine, to build something we didn’t think was possible.

In the silence of billions of NAND gates switching inside a processor, I saw a reflection of the contradictions we

carry in our own lives. The “no” that eventually becomes a bigger “yes.” The failure that leads to reinvention. The

paradoxes that sharpen innovation. Just as NAND, in its apparent simplicity, can give birth to the entire

complexity of computation, our own contradictions often shape the universality of who we are.

What feels like a locked door might be the master key. So every time I face a challenge, I remember NAND, not as a gate, but as a reminder

Universality can be hidden in constraint, and contradiction is not the end of logic, but the beginning of creation!