Hack Assembler (nand2tetris) — C++ / wxWidgets

A small assembler for the Hack computer from the nand2tetris course.

It translates Hack assembly (.asm) into Hack machine code (.hack). The project also includes a simple wxWidgets GUI for loading/pasting code, assembling it, previewing the output, and saving the result.

About this repo: This started as a student project while learning nand2tetris.

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What it can do

• Assemble Hack assembly (.asm) → machine code (.hack)
• Classic two-pass assembler
  • Pass 1: collect labels (LOOP) and resolve ROM addresses
  • Pass 2: translate A/C instructions and allocate variables
• Symbol table
  • Predefined symbols: SP, LCL, ARG, THIS, THAT, R0..R15, SCREEN, KBD
  • User labels: (LABEL)
  • User variables: allocated starting at RAM[16]
• GUI
  • open .asm file or paste code
  • assemble
  • preview .hack output
  • save output
  • shows a simple symbol-table dump (SymbolTable.txt)

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How it works (quick overview)

Main pipeline is implemented in Assembler.cpp:

1. Cleanup (Assembler::asmEdit)
   • removes comments (// ...)
   • removes spaces
   • stores non-empty lines in a queue
2. First pass (Assembler::firstPass)
   • detects labels like (LOOP)
   • stores label -> ROM address
   • produces a second queue without label lines
3. Second pass (Assembler::secondPass)
   • translates each instruction via Parser::parseInst
   • writes 16-bit machine code to the output file

A-instructions

• @123 → 0 + 15-bit value
• @symbol → resolved with the symbol table
  • new variables are allocated starting at address 16

C-instructions

Encoded as:

• 111 + comp (7 bits) + dest (3 bits) + jump (3 bits)

The lookup tables for comp, dest, jump are implemented in Parser.cpp.

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Project structure

• Assembler.* — two-pass assembler pipeline + symbol dump (SymbolTable.txt)
• Parser.* — parsing A/C instructions + comp/dest/jump dictionaries
• SymbolTable.* — predefined symbols + label/variable allocation
• MainFrame.*, App.* — wxWidgets GUI
• testAsm/ — small example programs for manual testing

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Building / running (Windows)

This repository contains a Visual Studio project:

• V45k3 - Assembler.vcxproj

General steps:

1. Open the .vcxproj in Visual Studio
2. Install/configure wxWidgets for your toolset
3. Build and run

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Examples

Example input programs can be found in testAsm/ (Counting to 10, Fibonacci, etc.).

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Notes / limitations

• Hack is intentionally small; some computations do not exist.
  • Example: testAsm/Parity of number.asm contains D=D%A as a reminder/test case.
• The GUI currently writes temporary files into the working directory (e.g. temp.asm, output.hack, SymbolTable.txt).

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License

MIT — see LICENSE.