x86sim

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Simulator of x86 intel computer in a 16-bit real mode made for education purposes.

Made in svelte - sveltejs/component-template

Demo

You can try the simulator on this page

Features

• code editor
  • breakpoints
  • autocomplete
  • error checking
  • autosave, no need to manually save the project
• registers editor
  • implemented general-purpose registers (AX, BX, CX, DX), segment registers (CS, DS, SS, ES), flags (parity, zero, sign, overflow)
• memory editor
  • memory size 1 MB (so segment registers need to be used) - same as the largest memory addressable by Intel 8086
• stack segment (different view to the same memory)
• keyboard
  • read status (if keyboard has available input) at port 0x64
  • read input byte at port 0x60
• screen (text graphics adapter)
  • colors
  • memory-mapped from address 0xb8000
• running the code
  • infinite loop detection (simulator won't "freeze")
  • "instant" code executions or animated (delayed) code execution
  • follow IP register setting
  • ability to undo code execution ("step back" and "run backwards")
  • debugging mode - changes to registers, memory, and keyboard buffer are restored to the state before the "debugging mode"
• help and tutorial
  • 22 included tutorial projects
  • Guide directly inside simulator
• all projects saved in the browsers (permanent) localStorage
  • all projects can be exported as ZIP/JSON
  • exported projects can be imported by drag & drop to the window of the simulator
• English and Slovak internationalization
• Dark theme :)
• Speed
• Offline support using service worker (index.html can't be inside a subfolder of the webserver, subdomain is ok)

Limitations

• Variable-length instructions are not implemented (every instruction is 1 byte in length, but shouldn't be. x86 instructions can be up to 15 bytes in length)
• compiled assembly code cannot be seen inside the main memory
• not all flags from the flag register are implemented (missing carry flag, ac, ...)
• limited amount of implemented instructions
• doesn't work on touch devices ("ace" code editor needs to be updated, provide an alternative for drag & drop to import projects to the simulator)

Future plans

• Translate built-in guide to English
• Add support for touch devices
• Implement carry flag
• Implement ability to run multiple instances of application logic

Building from source

First setup

• git clone https://github.com/slatinsky/x86sim
• cd x86sim
• npm i

Development build

• npm run dev
• you are now ready to modify the code. The browser will be automatically reloaded
• if you add a new typescript file, you may need to restart npm run dev

Production build

to create optimized production build including service workers for offline support:

• npm run build
• copy files from the public folder to your webserver

Running tests

• npm t
• all .spec.ts files are test files

More in-depth development environment guide

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Found a bug? Please create an issue

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