Assembly Studio

Write, build, run and debug 8086 assembly programs, in one window, fully offline.

Assembly Studio is a free, open-source Windows IDE for learning assembly language. Write a DOS .COM program in NASM syntax, build it with the bundled NASM, run it on an emulated 8086 PC, then step through it while registers, flags, memory, the stack and your variables update, with every change marked.

Website: https://assembly-studio-one.vercel.app

Download

Get AssemblyStudio-1.0.1-setup.exe from the latest release.

• SHA-256: 17f4f02ed28c69f0a155f2106ab76d7a3303b424e4a15026c2efa5d780990370
• No administrator rights needed. It installs for your Windows account and downloads nothing. The .NET runtime and NASM 3.02 are included.
• The installer is not code-signed, so Windows SmartScreen may warn you. Choose More info, then Run anyway. See the install guide.

Features

• Editor:
  • NASM syntax highlighting, line numbers, the current line marked;
  • undo and redo, block indent;
  • find and replace, go to line, zoom;
  • tabs, recent files, and recovery of unsaved edits after a crash.
• Build with one key:
  • errors and warnings appear on their source lines, each with a plain next step;
  • a hint when the code looks like MASM or TASM.
• Run safely:
  • programs run inside an emulated 8086 (1 MB, real mode) and can never touch your files or network;
  • an instruction budget pauses endless loops, and the IDE never freezes.
• Debug:
  • Step Into, Step Over, breakpoints;
  • the current instruction with its disassembly, and an execution history.
• See inside the machine:
  • registers (with their 8-bit halves) in hex, decimal or binary;
  • flags, memory (hex and ASCII) and the stack;
  • a Variables panel that lists your program's data labels with their values.
• DOS text services: INT 21h functions 00h, 01h, 02h, 07h, 08h, 09h, 0Ah and 4Ch, INT 20h and Ctrl-C, with a console that accepts keyboard input.
• Learn: 8 sample programs, 5 tutorials, an instruction and concept reference, and help pages, all offline.
• Accessible:
  • every workflow by keyboard, with a visible focus;
  • screen-reader names and announcements;
  • dark, light and high-contrast themes.

Quick start

1. Install and start Assembly Studio.
2. Open the Learn sidebar (View → Learn Sidebar, or Ctrl+Alt+L) and choose the sample Hello, World.
3. Press F5 to build and run it. The output appears in the Console panel.
4. Press F11 to step one instruction at a time and watch the registers change.

The Hello, World sample:

org 100h                    ; a .COM program starts at offset 100h

    mov dx, message         ; DS:DX = address of the text
    mov ah, 09h             ; DOS function 09h: print text up to the '$'
    int 21h

    mov ax, 4C00h           ; DOS function 4Ch: end the program, exit code 0 (AL)
    int 21h

message db 'Hello, World!', 13, 10, '$'   ; 13, 10 = carriage return, line feed

Key	Action
Ctrl+Shift+B	Build
F5	Run / Continue
F11 / F10	Step Into / Step Over
F9	Toggle breakpoint

What is supported

• Processor: Intel 8086, real mode. Every documented 8086 instruction except IN, OUT and the 8087 (ESC) instructions.
• Programs: DOS .COM programs of up to 65,278 bytes, in NASM syntax.
• Services: the DOS text functions above. No files, disks, clock or BIOS services (INT 10h, INT 16h).
• Windows: 64-bit Windows 11, or Windows 10 21H2 or later. Releases 1.0.0 and 1.0.1 were tested on Windows 11.

See the known limitations and the release notes.

Build from source

You need: Windows 10 or 11 x64, the .NET SDK 10.0.403 (pinned in global.json) and PowerShell.

git clone https://github.com/Ahmad4085/assembly-studio.git
cd assembly-studio
powershell -ExecutionPolicy Bypass -File build/fetch-nasm.ps1           # NASM 3.02, checked against its SHA-256
dotnet build AssemblyStudio.slnx -c Release
dotnet run --project src/AssemblyStudio.App -c Release

Tests:

powershell -ExecutionPolicy Bypass -File build/fetch-singlesteptests.ps1   # 8086 hardware test data for the engine tests
powershell -ExecutionPolicy Bypass -File build/test.ps1                    # the whole suite

Installer:

powershell -ExecutionPolicy Bypass -File build/fetch-innosetup.ps1
powershell -ExecutionPolicy Bypass -File build/installer/build-installer.ps1

build-installer.ps1 also regenerates the third-party notices, the license inventory and the SBOM from the published files.

How it is built

• Platform: C# on .NET 10, WPF with MVVM, and AvalonEdit for the editor.
• Execution: a custom 8086 core, checked against hardware test data (SingleStepTests).
• Assembler: the bundled NASM.

The parts are separate projects behind interfaces:

Project	Role
AssemblyStudio.Engine.I8086	The CPU
AssemblyStudio.Runtime	Memory, the loader, interrupts
AssemblyStudio.Os.Dos	DOS services
AssemblyStudio.Toolchain.Nasm	NASM integration and source mapping
AssemblyStudio.Debugging	Debug sessions
AssemblyStudio.Content	Samples, tutorials and help
AssemblyStudio.App	The WPF user interface

A rule throughout: the panels only ever show state produced by the real engine, never invented values.

The project follows a documentation-driven, phase-gated process:

• requirements, architecture decisions (ADRs), design, plan, test and QA reports are all in docs/;
• the rules for contributors and AI coding agents are in AGENTS.md.

License

Assembly Studio is released under the MIT License. It includes:

• the Microsoft .NET runtime and WPF;
• AvalonEdit, CommunityToolkit.Mvvm and Iced;
• NASM 3.02.

Their licenses are listed in THIRD-PARTY-NOTICES.txt and in the app under Help → About. Six .NET runtime files are under Microsoft's terms, which you accept in the installer.