You will first need the mBed serial port driver available on your machine. In Windows 10, Windows Update will fetch the driver. 

For earlier versions,  or if you have used mBed before and upgraded, you may need to re-install the driver. 

Once you have installed this driver, the micro:bit will also appear in device-manager as a COM port, and you can use any terminal emulator program to send and receive data to and from the micro:bit over the USB serial lead, using the 'serial' language capabilities of many of our standard coding languages.

When installing the Windows mbed driver, you should make sure that the micro:bit is plugged into the USB port first, before trying to install the driver - some users have experienced 'unknown install errors' of this driver, and it seems to be related to not having the micro:bit actually plugged in at the time you do the install. You will also need full admin rights on your PC to install the driver.  

For example in Tera Term:

  1. Plug in micro:bit and open Tera Term
  2. Select Serial as the port
  3. Choose Setup > Serial port from the setting menu and configure these settings:
  •  Baud rate  = 115200
  • Data = 8 bits
  • Parity  = none
  • Stop  = 1 bit

You should now see serial data output in the console.

Further Information

mBed documentation 

Keywords for search: USB, serial port, Windows, REPL, Mu