Nand2Tetris Overview

This section guides you through implementing the Nand2Tetris course using Hardcaml. You’ll build a complete computer starting from a single NAND gate.

What is Nand2Tetris?

Nand2Tetris (also known as “The Elements of Computing Systems”) teaches you how computers work by having you build one from scratch:

1. Project 1 - Boolean Logic (NOT, AND, OR, XOR, MUX, DMUX)
2. Project 2 - Arithmetic (HalfAdder, FullAdder, ALU)
3. Project 3 - Memory (DFF, Register, RAM)
4. Project 5 - CPU and Computer

Why Hardcaml?

The original N2T course uses HDL (Hardware Description Language). Hardcaml provides:

• Type safety - Catch wiring errors at compile time
• Better tooling - Real IDE with syntax highlighting
• Powerful testing - Waveform visualization built-in
• Real HDL output - Generate Verilog for synthesis

How It Works

The N2t_chips Library

All chips are available through the N2t_chips module:

(* Use helper functions for concise syntax *)
let not_a = N2t_chips.not_ scope i.a
let and_ab = N2t_chips.and_ scope i.a i.b

(* Or use modules directly *)
let o = N2t_chips.Not.create scope { N2t_chips.Not.I.a = i.a }

Exercise Structure

Each chip has:

• Stub - Template code you complete (Nand2Tetris exercises)
• Solution - Reference implementation (Nand2Tetris Solutions)
• Test - Pre-written tests to verify your implementation

Key Convention

N2T and Hardcaml have different MUX conventions:

Convention	sel=0	sel=1
N2T	out = a	out = b
Hardcaml mux2	out = low	out = high

The mux16_ helper follows N2T convention, so use it for clarity.

Getting Started

1. Open the IDE
2. Select a chip from “Nand2Tetris” dropdown
3. Implement the create function using N2t_chips.Nand.nand
4. Click Run to test
5. Check “Nand2Tetris Solutions” to compare

Project Overview

Project 1: Logic Gates

Build all basic gates from NAND: NOT, AND, OR, XOR, MUX, DMUX, plus 16-bit variants.

Project 2: ALU

Build arithmetic circuits: HalfAdder, FullAdder, Add16, Inc16, and the ALU.

Project 3: Memory

Build sequential circuits: DFF, Bit, Register, RAM8 through RAM16K, and PC.

Project 5: CPU and Computer

Build the complete Hack computer: Memory (RAM/Screen/Keyboard), CPU, and the full Computer system.

Tips for Success

1. Start simple - NOT is just NAND(a, a)
2. Build hierarchically - Use previous chips to build new ones
3. Check waveforms - Visual debugging is your friend
4. Compare solutions - Learn from the reference implementations