Is Nand2Tetris Worth It? A Complete Review for Learning Computers From First Principles

Mar 21, 2026

Cowrie

Dev @ Bswen

Problem

Most developers use computers every day without understanding how they actually work. We write code in high-level languages, call APIs, and trust that somewhere beneath it all, magic happens. When something breaks at a low level—a memory leak, a stack overflow, a CPU instruction—we’re stuck.

I spent years in this state. I could build web applications, but I didn’t really understand what was happening underneath. What does a CPU actually do? How does memory store values? Why does a compiler need an assembler first?

Textbooks explain these concepts with diagrams and abstractions. But diagrams don’t build intuition. I needed to build a computer myself—from the ground up.

That’s what Nand2Tetris offers. The question is: is it worth 100+ hours of your time?

What is Nand2Tetris?

Nand2Tetris (officially “The Elements of Computing Systems”) is a course where you build a complete computer system from scratch. You start with a single NAND gate and progressively build:

• Logic gates (AND, OR, NOT, XOR, multiplexers)
• Arithmetic Logic Unit (ALU)
• Memory (RAM, registers)
• A complete CPU
• An assembler
• A virtual machine
• A compiler
• An operating system
• Applications (games, tools)

By the end, you’ve built every layer of a computer. No magic. No black boxes.

The course is free online, with optional paid certificates through Coursera. The book is optional but helpful for deeper explanations.

What You Actually Build

Here’s the complete project breakdown:

Project	What You Build	Key Concepts	Difficulty
1	Logic gates from NAND	Boolean algebra, combinational logic	Easy
2	Boolean arithmetic	Adders, ALU, combinational chips	Easy-Medium
3	Sequential logic	Flip-flops, RAM, program counter	Medium
4	Machine language	Hack assembly, I/O handling	Medium
5	Computer architecture	CPU, memory, instruction cycle	Medium-Hard
6	Assembler	Symbol table, binary translation	Medium
7	Virtual Machine I	Stack arithmetic, memory segments	Medium-Hard
8	Virtual Machine II	Program flow, function calling	Hard
9	High-level language	Jack language, OOP basics	Medium
10	Compiler I	Lexical analysis, parsing	Hard
11	Compiler II	Code generation, symbol tables	Hard
12	Operating System	Syscalls, memory management, math	Hard

Each project builds on the previous one. You can’t skip projects because your assembler won’t work without the computer, and your compiler won’t work without the virtual machine.

Why It Works: First-Principles Learning

The genius of Nand2Tetris is abstraction management. Each project introduces exactly one new abstraction layer:

NAND Gate
    ↓ (Project 1-2: Build gates, adders, ALU)
Hardware Platform
    ↓ (Project 3-4: Add memory, machine language)
Computer
    ↓ (Project 5-6: Build CPU, assembler)
Assembler Language
    ↓ (Project 7-8: Virtual machine, stack)
VM Language
    ↓ (Project 9-11: High-level language, compiler)
Jack Language
    ↓ (Project 12: Operating system)
Complete Computer System

You never have more than one black box at a time. When you build the CPU in Project 5, you already understand every component because you built them in Projects 1-4.

Code Examples: What You Actually Write

Building an AND Gate from NAND

In Project 1, you start with only NAND gates. Your first task: build everything else.

And.hdl

CHIP And {
    IN a, b;
    OUT out;

    PARTS:
    Nand(a=a, b=b, out=nandOut);
    Not(in=nandOut, out=out);
}

The logic is simple: NAND(a, b) = NOT(AND(a, b)), so AND(a, b) = NOT(NAND(a, b)). But implementing this yourself makes it real.

Building Memory: A Single Bit

Project 3 introduces sequential logic. Here’s a 1-bit register:

Bit.hdl

CHIP Bit {
    IN in, load;
    OUT out;

    PARTS:
    Mux(a=feedbackOut, b=in, sel=load, out=muxOut);
    DFF(in=muxOut, out=out, out=feedbackOut);
}

This blew my mind. A DFF (Data Flip-Flop) stores state by feeding its output back through a multiplexer. When load=1, it captures the new input. When load=0, it keeps the previous value.

The RAM chips stack these:

RAM8.hdl

CHIP RAM8 {
    IN in[16], load, address[3];
    OUT out[16];

    PARTS:
    DMux8Way(in=load, sel=address, a=l0, b=l1, c=l2, d=l3, e=l4, f=l5, g=l6, h=l7);
    Register(in=in, load=l0, out=r0);
    Register(in=in, load=l1, out=r1);
    Register(in=in, load=l2, out=r2);
    Register(in=in, load=l3, out=r3);
    Register(in=in, load=l4, out=r4);
    Register(in=in, load=l5, out=r5);
    Register(in=in, load=l6, out=r6);
    Register(in=in, load=l7, out=r7);
    Mux8Way16(a=r0, b=r1, c=r2, d=r3, e=r4, f=r5, g=r6, h=r7, sel=address, out=out);
}

Eight registers, three-bit addressing. Scale this to 16K and you have the RAM in your computer.

The ALU: Computing Everything

Project 2’s ALU performs all arithmetic and logic operations with just six control bits:

ALU.hdl

CHIP ALU {
    IN
        x[16], y[16],
        zx,   // zero the x input
        nx,   // negate the x input
        zy,   // zero the y input
        ny,   // negate the y input
        f,    // function: 1 = add, 0 = and
        no;   // negate the output
    OUT
        out[16],
        zr,   // 1 if out == 0
        ng;   // 1 if out < 0

    PARTS:
    // Implementation uses the control bits to transform inputs
    // then add or and them, then optionally negate
    Not16(in=x, out=notX);
    Mux16(a=x, b=notX, sel=nx, out=xAfterNx);
    // ... (full implementation continues)
}

Six control bits give you 18 operations: add, subtract, and, or, not, increment, decrement, and more. All arithmetic reduces to these operations.

The Assembler: Translating Symbols

Project 6 builds an assembler that converts Hack assembly to binary:

Assembly Input

@R0       // A-instruction: load address of R0
D=M       // C-instruction: D = RAM[0]
@R1       // A-instruction: load address of R1
D=D-M     // C-instruction: D = D - RAM[1]
@OUTPUT_FIRST  // Label (symbol)
D;JGT     // If D > 0, jump to OUTPUT_FIRST
@R1
D=M
@R2
M=D       // RAM[2] = RAM[1]
@END
0;JMP     // Unconditional jump
(OUTPUT_FIRST)
@R0
D=M
@R2
M=D       // RAM[2] = RAM[0]
(END)
@END
0;JMP     // Infinite loop

assembler.py

def assemble(input_file: str) -> list[str]:
    """Convert Hack assembly to binary machine code."""
    symbol_table = init_symbols()  # Predefined symbols
    binary_output = []
    rom_address = 0

    # First pass: build symbol table for labels
    for line in clean_lines(input_file):
        if line.startswith('('):
            label = line[1:-1]
            symbol_table[label] = rom_address
        else:
            rom_address += 1

    # Second pass: generate binary
    for line in clean_lines(input_file):
        if line.startswith('@'):
            # A-instruction
            symbol = line[1:]
            if symbol.isdigit():
                value = int(symbol)
            else:
                if symbol not in symbol_table:
                    symbol_table[symbol] = allocate_variable()
                value = symbol_table[symbol]
            binary_output.append(f'{value:016b}')
        elif not line.startswith('('):
            # C-instruction: dest=comp;jump
            binary_output.append(encode_c_instruction(line))

    return binary_output

The assembler handles two types of symbols:

• Labels: (LOOP), (END) - jump targets
• Variables: @counter, @sum - automatically allocated in RAM

The Jack Language: A Simple OOP Language

Project 9 introduces Jack, a simple object-oriented language:

Main.jack

class Main {
    function void main() {
        var Array a;
        var int length;
        var int i, sum;

        let length = 10;
        let a = Array.new(length);
        let sum = 0;
        let i = 0;

        while (i < length) {
            let a[i] = i * 2;
            let sum = sum + a[i];
            let i = i + 1;
        }

        do Output.printInt(sum);
        return;
    }
}

Jack compiles to VM code, which the VM translator converts to assembly, which the assembler converts to binary. You build every layer.

Time Investment vs. Value

Here’s the realistic time commitment:

Commitment Level	Projects	Hours	What You Get
Hardware only	1-5	~50	CPU, memory, machine code understanding
Part 1 Complete	1-6	~60	Full hardware + assembler
Part 2 Complete	7-12	~60	VM, compiler, OS
Full Course	1-12	~100-120	Complete computer system
Deep Dive	1-12 + extensions	~150+	All above + optimizations, games

Most people complete the course in 2-4 months, working 5-10 hours per week.

What Makes Nand2Tetris Different

I’ve tried learning computer architecture from textbooks. They show diagrams like this:

CPU ←→ Memory ←→ I/O

Nand2Tetris forces you to build the arrows. You understand what ”←→” actually means.

True First Principles

Every other course starts with assumptions. “Assume you have a CPU.” “Assume you have memory.” Nand2Tetris starts with NAND:

NAND = NOT(AND)

Everything else derives from this. You prove it by building it.

Hands-On Every Step

No slides. No passive videos. You write code for every project. The simulator runs your chips and tells you exactly what’s wrong:

Test Output

Comparison failure at line 23:
  Expected: 0000000000000001
  Actual:   0000000000000000

This immediate feedback loop accelerates learning.

Complete Vertical Slice

Most courses teach one layer deeply. Nand2Tetris teaches all layers connected:

High-level Language (Jack)
         ↓
      Compiler
         ↓
   Virtual Machine
         ↓
     Assembler
         ↓
   Machine Code
         ↓
    CPU (you built)
         ↓
  Memory (you built)
         ↓
 Logic Gates (you built)
         ↓
     NAND Gate

You see how high-level code becomes electrical signals.

Common Mistakes to Avoid

Based on my experience and the community forums:

Mistake	Why It Hurts	What to Do Instead
Rushing through projects	Each layer depends on previous ones	Take time to understand before moving on
Skipping hardware projects	You won’t understand what the CPU does	Complete Projects 1-5 thoroughly
Expecting professional tools	Hack is simplified for learning	Embrace the simplicity; it teaches concepts
Going alone without community	You’ll get stuck on trivial issues	Join Discord, use forums
Copying solutions	No learning happens	Struggle first, then peek if needed
Not finishing the OS	The payoff comes at the end	Push through Projects 10-12

The biggest mistake: treating this like a tutorial. It’s not. It’s a construction project. You’re building something real.

Who Should Take Nand2Tetris

Strong fit:

• Software engineers wanting deeper understanding
• CS students supplementing coursework
• Self-taught developers filling knowledge gaps
• Anyone curious about how computers work
• Career changers entering tech

Weaker fit:

• Complete programming beginners (learn basic coding first)
• Those wanting immediate job skills (not practical for day-to-day)
• People who learn better from videos than building

Prerequisites? None officially. But familiarity with basic programming helps. If you’ve never written a for-loop, start with a programming course first.

What You Gain

After completing Nand2Tetris:

Demystified Computing: The “magic” is gone. You know how a CPU executes instructions, how memory stores data, how a compiler translates code.

Debugging Superpowers: When you see a stack overflow, you understand the stack. When you see a memory error, you know what RAM looks like.

Interview Confidence: CPU questions, memory management, compilation—topics that used to intimidate you become answerable.

Foundation for Advanced Topics: Operating systems, compilers, computer architecture courses all become accessible.

Portfolio Piece: You built a computer. That’s a conversation starter.

How to Approach the Course

Based on my experience:

1. Set up your environment properly. Use their provided tools first, then explore alternatives.

2. Read the book chapters. The projects assume you’ve read the theory. Skipping leads to frustration.

3. Start each project by understanding the test cases. The .tst and .cmp files tell you exactly what success looks like.

4. Debug systematically. When your chip fails, isolate which output bit is wrong and trace backward.

5. Use the community. The Discord and forums have thousands of people who’ve hit the same walls.

6. Take breaks. Some projects (especially 7-8 and 10-11) are mentally taxing. Step away and return fresh.

7. Celebrate milestones. When your CPU boots its first program, that’s a real achievement.

Summary

In this post, I reviewed whether Nand2Tetris is worth the investment. The answer is yes—for anyone who wants to truly understand how computers work.

The course takes approximately 100 hours, requires no prerequisites beyond basic programming, and gives you hands-on experience building a complete computer system from NAND gates to an operating system. You implement every layer: logic gates, ALU, memory, CPU, assembler, virtual machine, compiler, and OS.

What makes it unique: true first-principles learning, hands-on construction at every step, and a complete vertical slice through all computing layers. No black boxes remain.

The value isn’t in job skills—it’s in deep understanding. After Nand2Tetris, you’ll never look at a computer the same way. Every abstraction becomes concrete. Every mystery becomes machinery.

Final Words + More Resources

My intention with this article was to help others share my knowledge and experience. If you want to contact me, you can contact by email: Email me

Here are also the most important links from this article along with some further resources that will help you in this scope:

• 👨‍💻 Nand2Tetris Official Website
• 👨‍💻 The Elements of Computing Systems (Book)
• 👨‍💻 Nand2Tetris Course on Coursera
• 👨‍💻 Nand2Tetris Community on Discord

Oh, and if you found these resources useful, don’t forget to support me by starring the repo on GitHub!

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