To begin coding in C++ using the micro:bit, you will need to set up the relevant toolchains on your computer.
This may be different depending on which variant of the micro:bit you are compiling for.
The micro:bit runtime (DAL) provides documentation for the offline toolchain which can be used with V1 boards.
The micro:bit V2 samples repository provides instructions on how to build for V2 boards.
Examples
These repositories contain sample programs that you can compile for each board variant.
V1
https://github.com/lancaster-university/microbit-samples
V2
https://github.com/lancaster-university/microbit-v2-samples
Keywords for search: C, C++, runtime, DAL, lancaster, IDE, mbed, compile