All data items are held in the native byte order of the AVR processor. The plain character type is signed by default. The floating-point types float and double are implemented as 32-bit and 64-bit IEEE floating-point.

Data Type Size in bytes Alignment in bytes
char, signed char, and unsigned char 1 1
int and unsigned int 2 1
short and unsigned short 2 1
long and unsigned long 4 1
long long and unsigned long long 8 1
float and double (compiled with -msd) 4 1
double and long double 8 1
type * (pointer) 2 1
enum (enumeration) 2 1