# b4 virtual machine **Source:** https://github.com/tangentstorm/b4 GitHub - tangentstorm/b4: b4 : a tiny forth-like virtual machine [Skip to content](#start-of-content) ## Navigation Menu Toggle navigation [Sign in](/login?return_to=https%3A%2F%2Fgithub.com%2Ftangentstorm%2Fb4) Appearance settings * Platform + AI CODE CREATION - [GitHub CopilotWrite better code with AI](https://github.com/features/copilot) - [GitHub SparkBuild and deploy intelligent apps](https://github.com/features/spark) - [GitHub ModelsManage and compare prompts](https://github.com/features/models) - [MCP RegistryNewIntegrate external tools](https://github.com/mcp) + DEVELOPER WORKFLOWS - [ActionsAutomate any workflow](https://github.com/features/actions) - [CodespacesInstant dev environments](https://github.com/features/codespaces) - [IssuesPlan and track work](https://github.com/features/issues) - [Code ReviewManage code changes](https://github.com/features/code-review) + APPLICATION SECURITY - [GitHub Advanced SecurityFind and fix vulnerabilities](https://github.com/security/advanced-security) - [Code securitySecure your code as you build](https://github.com/security/advanced-security/code-security) - [Secret protectionStop leaks before they start](https://github.com/security/advanced-security/secret-protection) + EXPLORE - [Why GitHub](https://github.com/why-github) - [Documentation](https://docs.github.com) - [Blog](https://github.blog) - [Changelog](https://github.blog/changelog) - [Marketplace](https://github.com/marketplace) [View all features](https://github.com/features) * Solutions + BY COMPANY SIZE - [Enterprises](https://github.com/enterprise) - [Small and medium teams](https://github.com/team) - [Startups](https://github.com/enterprise/startups) - [Nonprofits](https://github.com/solutions/industry/nonprofits) + BY USE CASE - [App Modernization](https://github.com/solutions/use-case/app-modernization) - [DevSecOps](https://github.com/solutions/use-case/devsecops) - [DevOps](https://github.com/solutions/use-case/devops) - [CI/CD](https://github.com/solutions/use-case/ci-cd) - [View all use cases](https://github.com/solutions/use-case) + BY INDUSTRY - [Healthcare](https://github.com/solutions/industry/healthcare) - [Financial services](https://github.com/solutions/industry/financial-services) - [Manufacturing](https://github.com/solutions/industry/manufacturing) - [Government](https://github.com/solutions/industry/government) - [View all industries](https://github.com/solutions/industry) [View all solutions](https://github.com/solutions) * Resources + EXPLORE BY TOPIC - [AI](https://github.com/resources/articles?topic=ai) - [Software Development](https://github.com/resources/articles?topic=software-development) - [DevOps](https://github.com/resources/articles?topic=devops) - [Security](https://github.com/resources/articles?topic=security) - [View all topics](https://github.com/resources/articles) + EXPLORE BY TYPE - [Customer stories](https://github.com/customer-stories) - [Events & webinars](https://github.com/resources/events) - [Ebooks & reports](https://github.com/resources/whitepapers) - [Business insights](https://github.com/solutions/executive-insights) - [GitHub Skills](https://skills.github.com) + SUPPORT & SERVICES - [Documentation](https://docs.github.com) - [Customer support](https://support.github.com) - [Community forum](https://github.com/orgs/community/discussions) - [Trust center](https://github.com/trust-center) - [Partners](https://github.com/partners) * Open Source + COMMUNITY - [GitHub SponsorsFund open source developers](https://github.com/sponsors) + PROGRAMS - [Security Lab](https://securitylab.github.com) - [Maintainer Community](https://maintainers.github.com) - [Accelerator](https://github.com/accelerator) - [Archive Program](https://archiveprogram.github.com) + REPOSITORIES - [Topics](https://github.com/topics) - [Trending](https://github.com/trending) - [Collections](https://github.com/collections) * Enterprise + ENTERPRISE SOLUTIONS - [Enterprise platformAI-powered developer platform](https://github.com/enterprise) + AVAILABLE ADD-ONS - [GitHub Advanced SecurityEnterprise-grade security features](https://github.com/security/advanced-security) - [Copilot for BusinessEnterprise-grade AI features](https://github.com/features/copilot/copilot-business) - [Premium SupportEnterprise-grade 24/7 support](https://github.com/premium-support) * [Pricing](https://github.com/pricing) Search or jump to... # Search code, repositories, users, issues, pull requests... 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Dismiss alert {{ message }} [tangentstorm](/tangentstorm) / **[b4](/tangentstorm/b4)** Public * [Notifications](/login?return_to=%2Ftangentstorm%2Fb4) You must be signed in to change notification settings * [Fork 4](/login?return_to=%2Ftangentstorm%2Fb4) * [Star 39](/login?return_to=%2Ftangentstorm%2Fb4) b4 : a tiny forth-like virtual machine [www.reddit.com/r/b4lang/](http://www.reddit.com/r/b4lang/ "http://www.reddit.com/r/b4lang/") [39 stars](/tangentstorm/b4/stargazers) [4 forks](/tangentstorm/b4/forks) [Branches](/tangentstorm/b4/branches) [Tags](/tangentstorm/b4/tags) [Activity](/tangentstorm/b4/activity) [Star](/login?return_to=%2Ftangentstorm%2Fb4) [Notifications](/login?return_to=%2Ftangentstorm%2Fb4) You must be signed in to change notification settings * [Code](/tangentstorm/b4) * [Issues 0](/tangentstorm/b4/issues) * [Pull requests 2](/tangentstorm/b4/pulls) * [Actions](/tangentstorm/b4/actions) * [Projects 0](/tangentstorm/b4/projects) * [Wiki](/tangentstorm/b4/wiki) * [Security 0](/tangentstorm/b4/security) * [Insights](/tangentstorm/b4/pulse) Additional navigation options * [Code](/tangentstorm/b4) * [Issues](/tangentstorm/b4/issues) * [Pull requests](/tangentstorm/b4/pulls) * [Actions](/tangentstorm/b4/actions) * [Projects](/tangentstorm/b4/projects) * [Wiki](/tangentstorm/b4/wiki) * [Security](/tangentstorm/b4/security) * [Insights](/tangentstorm/b4/pulse) # tangentstorm/b4 main [Branches](/tangentstorm/b4/branches)[Tags](/tangentstorm/b4/tags) Go to file Code Open more actions menu ## Folders and files | Name | | Name | Last commit message | Last commit date | | --- | --- | --- | --- | --- | | Latest commit History[1,568 Commits](/tangentstorm/b4/commits/main/) 1,568 Commits | | | | [b3a](/tangentstorm/b4/tree/main/b3a "b3a") | | [b3a](/tangentstorm/b4/tree/main/b3a "b3a") | | | | [bios](/tangentstorm/b4/tree/main/bios "bios") | | [bios](/tangentstorm/b4/tree/main/bios "bios") | | | | [doc](/tangentstorm/b4/tree/main/doc "doc") | | [doc](/tangentstorm/b4/tree/main/doc "doc") | | | | [electron](/tangentstorm/b4/tree/main/electron "electron") | | [electron](/tangentstorm/b4/tree/main/electron "electron") | | | | [etc](/tangentstorm/b4/tree/main/etc "etc") | | [etc](/tangentstorm/b4/tree/main/etc "etc") | | | | [jlang](/tangentstorm/b4/tree/main/jlang "jlang") | | [jlang](/tangentstorm/b4/tree/main/jlang "jlang") | | | | [js](/tangentstorm/b4/tree/main/js "js") | | [js](/tangentstorm/b4/tree/main/js "js") | | | | [lil](/tangentstorm/b4/tree/main/lil "lil") | | [lil](/tangentstorm/b4/tree/main/lil "lil") | | | | [mcp-b4i](/tangentstorm/b4/tree/main/mcp-b4i "mcp-b4i") | | [mcp-b4i](/tangentstorm/b4/tree/main/mcp-b4i "mcp-b4i") | | | | [pas](/tangentstorm/b4/tree/main/pas "pas") | | [pas](/tangentstorm/b4/tree/main/pas "pas") | | | | [ref](/tangentstorm/b4/tree/main/ref "ref") | | [ref](/tangentstorm/b4/tree/main/ref "ref") | | | | [.gitignore](/tangentstorm/b4/blob/main/.gitignore ".gitignore") | | [.gitignore](/tangentstorm/b4/blob/main/.gitignore ".gitignore") | | | | [ASSISTANTS.md](/tangentstorm/b4/blob/main/ASSISTANTS.md "ASSISTANTS.md") | | [ASSISTANTS.md](/tangentstorm/b4/blob/main/ASSISTANTS.md "ASSISTANTS.md") | | | | [README.org](/tangentstorm/b4/blob/main/README.org "README.org") | | [README.org](/tangentstorm/b4/blob/main/README.org "README.org") | | | | [b4-tests.org](/tangentstorm/b4/blob/main/b4-tests.org "b4-tests.org") | | [b4-tests.org](/tangentstorm/b4/blob/main/b4-tests.org "b4-tests.org") | | | | [b4i](/tangentstorm/b4/blob/main/b4i "b4i") | | [b4i](/tangentstorm/b4/blob/main/b4i "b4i") | | | | [b4i-tests.org](/tangentstorm/b4/blob/main/b4i-tests.org "b4i-tests.org") | | [b4i-tests.org](/tangentstorm/b4/blob/main/b4i-tests.org "b4i-tests.org") | | | | [b4ix](/tangentstorm/b4/blob/main/b4ix "b4ix") | | [b4ix](/tangentstorm/b4/blob/main/b4ix "b4ix") | | | | [b4s-tests.org](/tangentstorm/b4/blob/main/b4s-tests.org "b4s-tests.org") | | [b4s-tests.org](/tangentstorm/b4/blob/main/b4s-tests.org "b4s-tests.org") | | | | [bios-tests.org](/tangentstorm/b4/blob/main/bios-tests.org "bios-tests.org") | | [bios-tests.org](/tangentstorm/b4/blob/main/bios-tests.org "bios-tests.org") | | | | [goals.org](/tangentstorm/b4/blob/main/goals.org "goals.org") | | [goals.org](/tangentstorm/b4/blob/main/goals.org "goals.org") | | | | [init.b4i](/tangentstorm/b4/blob/main/init.b4i "init.b4i") | | [init.b4i](/tangentstorm/b4/blob/main/init.b4i "init.b4i") | | | | [plan.org](/tangentstorm/b4/blob/main/plan.org "plan.org") | | [plan.org](/tangentstorm/b4/blob/main/plan.org "plan.org") | | | | [pre-tests.org](/tangentstorm/b4/blob/main/pre-tests.org "pre-tests.org") | | [pre-tests.org](/tangentstorm/b4/blob/main/pre-tests.org "pre-tests.org") | | | | [test](/tangentstorm/b4/blob/main/test "test") | | [test](/tangentstorm/b4/blob/main/test "test") | | | | [test-b4-b4a](/tangentstorm/b4/blob/main/test-b4-b4a "test-b4-b4a") | | [test-b4-b4a](/tangentstorm/b4/blob/main/test-b4-b4a "test-b4-b4a") | | | | [test-b4-gd](/tangentstorm/b4/blob/main/test-b4-gd "test-b4-gd") | | [test-b4-gd](/tangentstorm/b4/blob/main/test-b4-gd "test-b4-gd") | | | | [test-b4-j](/tangentstorm/b4/blob/main/test-b4-j "test-b4-j") | | [test-b4-j](/tangentstorm/b4/blob/main/test-b4-j "test-b4-j") | | | | [test-b4-js](/tangentstorm/b4/blob/main/test-b4-js "test-b4-js") | | [test-b4-js](/tangentstorm/b4/blob/main/test-b4-js "test-b4-js") | | | | [test-b4-lil](/tangentstorm/b4/blob/main/test-b4-lil "test-b4-lil") | | [test-b4-lil](/tangentstorm/b4/blob/main/test-b4-lil "test-b4-lil") | | | | [test-b4-pas](/tangentstorm/b4/blob/main/test-b4-pas "test-b4-pas") | | [test-b4-pas](/tangentstorm/b4/blob/main/test-b4-pas "test-b4-pas") | | | | [test-b4i-js](/tangentstorm/b4/blob/main/test-b4i-js "test-b4i-js") | | [test-b4i-js](/tangentstorm/b4/blob/main/test-b4i-js "test-b4i-js") | | | | [test-b4i-lil](/tangentstorm/b4/blob/main/test-b4i-lil "test-b4i-lil") | | [test-b4i-lil](/tangentstorm/b4/blob/main/test-b4i-lil "test-b4i-lil") | | | | [test-b4i-pas](/tangentstorm/b4/blob/main/test-b4i-pas "test-b4i-pas") | | [test-b4i-pas](/tangentstorm/b4/blob/main/test-b4i-pas "test-b4i-pas") | | | | [test-b4s](/tangentstorm/b4/blob/main/test-b4s "test-b4s") | | [test-b4s](/tangentstorm/b4/blob/main/test-b4s "test-b4s") | | | | [test-bios](/tangentstorm/b4/blob/main/test-bios "test-bios") | | [test-bios](/tangentstorm/b4/blob/main/test-bios "test-bios") | | | | [test-pre](/tangentstorm/b4/blob/main/test-pre "test-pre") | | [test-pre](/tangentstorm/b4/blob/main/test-pre "test-pre") | | | | View all files | | | ## Repository files navigation * [README](#) # The b4 virtual machine # Demo [![ref/b4ix-rosetta.png](/tangentstorm/b4/raw/main/ref/b4ix-rosetta.png)](/tangentstorm/b4/blob/main/ref/b4ix-rosetta.png) The above screenshot is the `b4ix` enhanced interactive shell. The sceen is broken into three sections: * on top, a view into the systems video buffer, which is pre-initialized with a logo from the bios. * in the middle, an interactive shell for the `b4a` assembly language. * at the bottom, a view of stacks and section of the machine’s ram ## explanation of the demo code ``` # https://rosettacode.org/wiki/Loops/For :E lb 'e io rt # set up ^E to emit a character :I cd cd du dc sw dc rt # set up ^I to fetch outer loop counter :loop du .f du ^I sb c1 ad .f lb '. ^E .n lb '| ^E .n zp rt 5 loop ``` The `^E` syntax calls whatever function the `E` register is pointing at, and the assembler assigns it when it sees `:E`. Here, `^E` loads the byte `'e` (quoted ascii char) and sends that as a command to the `io` op, which prints the next character on the stack. The `^I` definition fetches the outer loop counter in a `.f` … `.n` (“for/next”) loop. Since it’s a function call, we have to dig deep into the control stack (`cd` means copy from control stack to data stack), (`du`)plicate the counter, and then (`sw`)ap it with the return address so we can push that back onto the control stack (`dc` means data -> control), and then `rt` (return). Then `:loop` dupes its argument and uses it as an argument to the `.f=/`.n= loop. During these loops, the loop counter is on the control stack, so `^I` grabs it as explained earlier, but there is also a copy of the original loop length (5 in this case) on the data stack. so `du ^I sb` duplicates the 5, subtracts the outer loop counter, and leaves the result on the stack. `c1` is an op that adds the constant 1 to the stack, and `ad` adds the top two values, so `c1 ad` adds 1 to the previous expression to get the length of the inner loop. `.f lb '. ^E .n` prints that many dots. `lb '| ^E .n` prints the pipe character and ends the outer loop. then `zp rt` removes that original `5` that’s been sitting on the stack the whole time (passed in when we explicitly called `5 loop`) and returns to the calling function (in this case, the interactive “b4ix” shell.) # About b4 **b4** is a tiny virtual machine, with a forth-like flavor. There are currently five implementations: * [./jlang/](/tangentstorm/b4/blob/main/jlang), implemented in [J](https://code.jsoftware.com/wiki/Main_Page). * [./pas/](/tangentstorm/b4/blob/main/pas), implemented in [free pascal](https://www.freepascal.org/). * [./lil/](/tangentstorm/b4/blob/main/lil), implemented in [lil](https://beyondloom.com/decker/lil.html). * [./js/](/tangentstorm/b4/blob/main/js), implemented in javascript. * [b4-gd](https://github.com/tangentstorm/b4-gd), implemented in GDScript for [Godot 4](https://docs.godotengine.org/en/stable/). The implementations are kept in sync through the tests in [./b4-tests.org](/tangentstorm/b4/blob/main/b4-tests.org) See [./bios/bios.b4a](/tangentstorm/b4/blob/main/bios/bios.b4a) for an example of b4 assembly language. # Links * [b4 github repo](https://github.com/tangentstorm/b4) * twitter: [@tangentstorm](https://twitter.com/tangentstorm) / [#b4lang](https://twitter.com/#!/search/realtime/%23b4lang) * reddit: [/r/b4lang](http://reddit.com/r/b4lang) # Background B4 is a forth-like virtual machine. Quick **intros to forth** (free and online): * [Programming a Problem-Oriented Language](http://www.colorforth.com/POL.htm) * [Starting Forth](http://www.forth.com/starting-forth/) B4 was strongly influenced by the [ngaro virtual machine](http://retroforth.org/docs/The_Ngaro_Virtual_Machine.html) from retroforth 11, as well as the [forth chips from greenarrays](https://www.greenarraychips.com/home/documents/index.php#architecture). ## About b4 : a tiny forth-like virtual machine [www.reddit.com/r/b4lang/](http://www.reddit.com/r/b4lang/ "http://www.reddit.com/r/b4lang/") ### Resources [Readme](#readme-ov-file) ### Uh oh! There was an error while loading. Please reload this page. [Activity](/tangentstorm/b4/activity) ### Stars [**39** stars](/tangentstorm/b4/stargazers) ### Watchers [**6** watching](/tangentstorm/b4/watchers) ### Forks [**4** forks](/tangentstorm/b4/forks) [Report repository](/contact/report-content?content_url=https%3A%2F%2Fgithub.com%2Ftangentstorm%2Fb4&report=tangentstorm+%28user%29) ## [Releases](/tangentstorm/b4/releases) No releases published ## [Packages 0](/users/tangentstorm/packages?repo_name=b4) No packages published ### Uh oh! There was an error while loading. Please reload this page. ## [Contributors 3](/tangentstorm/b4/graphs/contributors) ### Uh oh! There was an error while loading. Please reload this page. ## Languages * [Pascal 34.8%](/tangentstorm/b4/search?l=pascal) * [Python 22.4%](/tangentstorm/b4/search?l=python) * [JavaScript 10.7%](/tangentstorm/b4/search?l=javascript) * [TypeScript 8.5%](/tangentstorm/b4/search?l=typescript) * [Forth 7.8%](/tangentstorm/b4/search?l=forth) * [J 5.9%](/tangentstorm/b4/search?l=j) * Other 9.9% ## Footer © 2026 GitHub, Inc. ### Footer navigation * [Terms](https://docs.github.com/site-policy/github-terms/github-terms-of-service) * [Privacy](https://docs.github.com/site-policy/privacy-policies/github-privacy-statement) * [Security](https://github.com/security) * [Status](https://www.githubstatus.com/) * [Community](https://github.community/) * [Docs](https://docs.github.com/) * [Contact](https://support.github.com?tags=dotcom-footer) * Manage cookies * Do not share my personal information You can’t perform that action at this time.