AVR programming

The Baud rate: number of bytes per second. Typical is 9600

IMPORTANT HARDWARE REGISTERS:
DDRx: data-direction registers (port x)
  -configuration for input or output (data direction)
  -0 is input, 1 is output
  -default all 0s
  -ex value: 0b00100101 (0b: means binary literal next)
PORTx: port x data registers
  -on output: 1 - high, 0 - low 
  -on input: 1 - has internal pull-up resistor, 0 - hi-Z (high impedance state), disconnected from circuit (but can sense voltage)
  -default all 0s
PINx: port x input pins address
  -read only for input pins: 1 - high, 0 - low

*****Variables:
typedef signed char   int8_t
typedef unsigned char   uint8_t
typedef signed int  int16_t
typedef unsigned int  uint16_t
typedef signed long int   int32_t
typedef unsigned long int   uint32_t
typedef signed long long int  int64_t
typedef unsigned long long int  uint64_t

*****Headers for AVR:
find the include paths by typing: avr-cpp -v
  /usr/local/Cellar/avr-gcc/4.9.2/lib/gcc/avr/4.9.2/include
  /usr/local/Cellar/avr-gcc/4.9.2/lib/gcc/avr/4.9.2/../../../../avr/include
(http://www.amelek.gda.pl/avr/libc/avr-libc-reference.html#cos)
ctype.h Character type test functions
eeprom.h  EEPROM access functions
errno.h Error handling
ina90.h Compatibility header for IAR C
interrupt.h Interrupt handling routines
inttypes.h  Defines for different int data types
io-avr.h  Includes the correct ioXXX.h header
io.h  Includes other I/O-Headers
ioXXX.h I/O-Defines for various AVR microcontrollers
iomacros.h  Several macros for I/O access
math.h  Various mathematical functions
pgmspace.h  Compatibility header for IAR C
progmem.h Alias for pgmspace.h
setjmp.h  Provides functions for long jumps
sig-avr.h AVR interrupt and signal handling
signal.h  Alias for sig-avr.h. Should no longer be used.
stdlib.h  Miscellaneous routines
string-avr.h  String manipulation functions
string.h  More string manipulation routines
timer.h Timer control functions
twi.h ATmega163 specific defines
wdt.h Watchdog Timer control functions