This is avr-libc. It is a C library implementation for use with GNU GCC and GNU binutils for development of programs for Atmel's AVR microcontrollers. This library implements a subset of common C library functions, some Atmel AVR specific additions (like handling AVR's IO facilities, EEPROM etc.), as well as a 32-bit floating point math library (-lm). Everything is designed and implemented to cooperate with avr-gcc and avr-binutils. For details on installing and using AVR Libc, see the users manual in the doc/api directory or online at: http://savannah.nongnu.org/projects/avr-libc/