Uxn is the virtual machine powering the Hundred Rabbits software.

This one-page computer, programmable in Uxntal, is an portability layer with a focus on hosting graphical tools and games. It lives at the heart of the Varvara ecosystem.

• Uxn Instructions: Reference, Tests
• Varvara Devices: Reference, Tests

This wiki along with most of the audio-visual projects documented on it are running on Uxn.

Memory

Uxn utilizes two circular stacks of bytes, the return stack allows it to tunnel through 128 subroutines and find its way back, and 64kb of addressable working memory. It can interface with up to 16 peripherals, such as screens and controllers. Uxn's has no undefined behaviors, and cannot error.

Basic Emulator

Here is an implementation of a basic Uxn emulator in 150 lines of C which includes the Console device and passes the opcode tests. The complete emulator used to build this wiki can be found here.

cc uxnmin.c -o uxnmin view raw

Basic Assembler

Here is a self-hosted implementation of the assembler in 400 lines of Uxntal, capable of assembling itself.

cat uxnasm.tal | uxncli uxnasm.bin > uxnasm-bootstrap.rom view raw

Here is the 1.4kb binary data of the assembler above, alternatively, a new one can be created with uxnasm.c.

xxd -r -p uxnasm.rom uxnasm.tal view raw

Stack-machines programming make for an habitable bedrock abstraction for this scale of personal computing as one can comfortably write programs in assembly to tackle most computation projects with what feels like high-level abstractions.

Original illustrations created
by Rekka Bellum.

• Official Site
• Run in Browser
• Communities: Mailing List • Forum • irc.libera.chat #uxn
• Social: Discord • Github

• 17P04 — Uxn Specification Frozen
• 15B13 — Uxn is born!

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