This library contains a few example that shows how to write "pure" AVR C code using the Arduino IDE. It also contains a fairy large keywords.txt file which contains all register and bit names (and most library functions and definitions) for all microcontrollers supported by the MicroCore. The keywords file will make Arduino IDE highlight these bit and register names, making it easier to read and write AVR code using the IDE.

If you're using Arduino IDE 1.6.5 or lower, you'll have to select the ATtiny13 and restart the IDE in order to highlight the keywords.

There are some minor differences between the ATmega13 and the ATtiny13A. Read more about these differences in the AVR520 application note: http://www.atmel.com/Images/doc8157.pdf
