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in-browser compiler for BBC micro:bit

On November 18th, we rolled out the latest refresh of the BBC micro:bit web site and editors. It contains a bunch of fixes and improvements that were gathered through the various CAS hub training around the UK.

Making it easier to compile scripts...

Following the feedback from teachers, the following improvements were made:
  • compile without signing in
  • compile offline
  • save and load code using files

A new in-browser compiler

The compilation from the script to the ARM machine code is now done entirely in the browser thanks to the ARM thumb assembler written by Michał Moskal (read the in depth story about building the compiler). The new compiler is used by the Block Editor, Touch Develop and Code Kingdoms to create the .hex file on the fly without having to rely on an cloud-based C++ compiler.
The BBC micro:bit compilation process (see page 10 in the Quick Start book) has been updated below to reflect the new compiler architecture.
As a result of running the entire compilation process in the browser, the new compiler works completely offline.

Save and load code using files

The BBC micro:bit automatically saves and synchronizes scripts for signed in users through the cloud. Unfortunately, this scenario would not work always so we decided to also support files. Users are now able to import and export scripts as files. For example, they can simply email it or submit them in their classroom portal.
Compiled .hex files can also be imported back into the web site. This make it easy for a teacher to review the source of a script by simply drag and dropping the file into the editor.