Keywords
The following words are defined as keywords and should not be redefined in a sketch:
defined(ARDUINO) 1
defined(__AVR__) 1
defined(__AVR_ATMEGA168__) 1 for Uno or 0 for Mega
defined(NUM_ANALOG_INPUTS) 6 for Uno or 16 for Mega
FALSE 0
TRUE 1
LOW 0
HIGH 1
ARDUINO 100
TOTAL_ANALOG_PINSX // unused - default return value of 1
TOTAL_PORTS 14
INPUT 0
OUTPUT 1
INPUT_PULLUP 2
TOTAL_PINSX 20
SD_CARD_TYPE_SD1 1
SD_CARD_TYPE_SD2 2
SD_CARD_TYPE_SD3 3
PI 3.1415926535897932384626433832795
HALF_PI 1.570796326794896619231321691639
TWO_PI 6.283185307179586476925286766559
DEG_TO_RAD 0.017453292519943295769236907684886
RAD_TO_DEG 57.295779513082320876798154814105
NUM_ANALOG_INPUTS 6 for Uno or 16 for Mega
TCC 0
NULL 0
DAC0 66
DAC1 67
ARDUINO 100
__AVR__ 1
__AVR_ATmega328P__ 1 or 0
__AVR_ATMEGA168__ 0
NUM_ANALOG_INPUTS 6 or 16
__AVR_ARCH__ 100
__AVR_ENHANCED__ 0
false 0
true 1
__GNUC__ 4
__GNUC_MINOR__ 3
__INT_MAX__ 6
RASPBERRY_PI 0
WL_IDLE_STATUS 0
WL_CONNECTED 1
WL_NO_SHIELD -1
MAX_SOCK_NUM 4
PINA-L (no PINI)
DDRA-L (no DDRI)
PORTA-L (no PORTI)
defined( ... )