The BBC Micro bit an ARM-based embedded system designed by the BBC for use in computer education in the UK. The device has been given away free […] [to every 11 years old pupil] in the UK, and is also available for purchase by anyone.

This is the wikipedia definition.

With a 5×5 led matrix, two buttons, a compass and a 3-axis accelermeter, this small unit has a lot of interesting suff packed for less then 17€ on Amazon

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The core is an ARM CortexM with 16KB of RAM and 256KB of static flash for the code.

The Microbit web site offers a very huge set of videos and teaching material. But to regster you need to got an authorization code, because the site seems teacher-oriented, at least for publishing code samples.

It is not very easy to search for code samples, even if there is a bizzarre “site” index, who rememebrs me a 1995 web site :)

The micro:bit is plug and play: when you connect it on a PC  USB, a magic drive will appear. Simply copy your “hex” code on it and…no other steps are needed!

Comparing with an Arduino uno:

Pros

1. Four different web editor (Microsoft Blocks, Microsoft Touch Develop, Code Kingdoms JavaScript and MicroPython) to start.
   No C language knowledge required.
   Install nothing and get ready in seconds.
   Very easy upload procedure (is a simple drive copy!)
2. A lot more RAM then arduino (16Ks vs 2kBs)
3. 3-more pin on the bottom and +3V and GND to attach extra leds/sensor and so on
4. MicoPython-ready
   Very good collections of examples and demo at https://github.com/bbcmicrobit/micropython.The python runtime has a good hardware coverage too.
5. Low power: only 3Volt needed for operation (Arduino needs at least double as far as I know, anyway can work in a wider range and can output 3.xV and 5V).
6. Quite aggressive price.

Cons

1. Very difficult to download an off-line editor. The online editors use a custom format to save your code. In general the platform seems a bit too close for “ordinary” people. Arduino is much more open. Anyway the micropython is open source and only need a free account on ARM web site (mbed.org). Also my attempt to build the python editor was unsuccessful. The python editor lacks compilation checks anyway.
   I was able to build Micropython with a bit of work on MacOSX
2. Very very tiny.  For a 6/7 years old child is only “small”, for an adult is “tiny”.
3. To access the smaller pins like I2C you need additional stuff and/or precise soldering

Anyway I was very impressed. Every Europe school should get one.