Public | Automated Build

Last pushed: a year ago
Short Description
6502 Assembler and Simulator
Full Description


JBit comes in two main versions:

  • midp: A small java application for old feature phones (MIDlet)
    that gives you a programmable 8-bit microcomputer. You can edit, save, run and
    debug assembly (6502) programs directly on your phone.
    Note that this is not an app for modern Android/iPhone phones.

  • native: A 6502 assembler / simulator for the command line.
    On Linux(-like) systems it gives you easy access to a simplified subset
    of their kernel (read, fork, exec, etc...). This is also available to
    use on Android terminal apps.

Sharing some code with the native version is a new version of JBit:

  • io2sim: A libretro core simulating an
    useable subset of the midp version. A self-contained win32 executable
    linked with a minimal libretro front-end is also available.

Getting JBit

There is usually no need for you to build JBit from source.

A binary archive is available from
sourceforge and it
contains the most common binaries for midp, native (win32,
linux/android) and io2sim (win32), together with some documentation
and a few samples.
See dists/bin/template/README.txt for
more information.

If you need to download JBit directly from a feature phone, there is
a WAP site that you can use:
The main JBit web site is a XHTML site
designed with feature phones in mind and it is also very lightweight.

Building notes to generate the io2sim libretro core or to build the native
version of JBit on a Linux(-like) system can be found in


The native version of JBit is usually tested on the latest debian stable
and/or on ubuntu xenial (Bash on Windows).
In the past, it has been tested on:

  • Windows 95
  • Windows 10
  • Wine 1.6.2
  • DosBox v0.74
  • Slackware 2.2.0
  • NetBSD 1.6.2
  • OpenBSD 5.8
  • Mac OS X 10.8
  • Android 1.5+
  • Fire OS 5.1

The io2sim version of JBit is usually tested on Windows 10.
Occasionally, it is tested on:

  • RetroArch
  • Windows 95
  • DosBox v0.74

When the midp version of JBit is updated, it is usually tested on a
Samsung E2121B.
Occasionally, it is tested on:

  • Nokia 2630
  • Sony Ericsson K550
  • Motorola V360


A few docker images are available to ease
cross development (efornara/jbit):

main     Development setup for native (and basic documentation)
midp     Development setup for midp (Oracle WTK still needed)
droid    Development setup for Android (NDK cross compiler)
win32    Development setup for Win32 (mingw32 cross compiler)
dos      Development setup for MS-DOS (djgpp/watcom cross compilers)
doc      Development setup for extra documentation (sheets and mobi)

Even if you don't use docker, reading the files in
dists/docker can give you a few hints on how to setup
your own development environment.

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