5.5 Data Types

Table 5-1 lists the size, representation, and range of each scalar data type for the ARM compiler. Many of the range values are available as standard macros in the header file limits.h.

Table 5-1 ARM C/C++ Data Types

			Range
Type	Size	Representation	Minimum	Maximum
signed char	8 bits	ASCII	-128	127
char ⁽¹⁾	8 bits	ASCII	0 ⁽¹⁾	255 ⁽¹⁾
unsigned char	8 bits	ASCII	0	255
bool, _Bool	8 bits	ASCII	0 (false)	1(true)
short, signed short	16 bits	Binary	-32 768	32 767
unsigned short, wchar_t ⁽²⁾	16 bits	Binary	0	65 535
int, signed int	32 bits	Binary	-2 147 483 648	2 147 483 647
unsigned int	32 bits	Binary	0	4 294 967 295
long, signed long	32 bits	Binary	-2 147 483 648	2 147 483 647
unsigned long	32 bits	Binary	0	4 294 967 295
long long, signed long long	64 bits⁽³⁾	Binary	-9 223 372 036 854 775 808	9 223 372 036 854 775 807
unsigned long long	64 bits⁽³⁾	Binary	0	18 446 744 073 709 551 615
enum (TI_ARM9_ABI and TIABI only) ⁽⁴⁾	32 bits	Binary	-2 147 483 648	2 147 483 647
float	32 bits	IEEE 32-bit	1.175 494e-38⁽⁵⁾	3.40 282 346e+38
double	64 bits⁽³⁾	IEEE 64-bit	2.22 507 385e-308⁽⁵⁾	1.79 769 313e+308
long double	64 bits⁽³⁾	IEEE 64-bit	2.22 507 385e-308⁽⁵⁾	1.79 769 313e+308
pointers, references, pointer to data members	32 bits	Binary	0	0xFFFFFFFF

(1) "Plain" char has the same representation as either signed char or unsigned char. The --plain_char option specifies whether "plain" char is signed or unsigned. The default is unsigned.

(2) This is the default type for wchar_t. You can use the --wchar_t option to change the wchar_t type to a 32-bit unsigned int type.

(3) 64-bit data is aligned on a 64-bit boundary.

(4) For details about the size of an enum type, see Section 5.5.1. Also see Table 5-2 for sizes.

(5) Figures are minimum precision.

Negative values for signed types are represented using two's complement.

The type of the storage container for an enumerated type is the smallest integer type that contains all the enumerated values. The container types for enumerators are shown in Table 5-2.

Table 5-2 Enumerator Types

Lower Bound Range	Upper Bound Range	Enumerator Type
0 to 255	0 to 255	unsigned char
-128 to 1	-128 to 127	signed char
0 to 65 535	256 to 65 535	unsigned short
-128 to 1	128 to 32 767	short, signed short
-32 768 to -129	-32 768 to 32 767	short, signed short
0 to 4 294 967 295	2 147 483 648 to 4 294 967 295	unsigned int
-32 768 to -1	32 767 to 2 147 483 647	int, signed int
-2 147 483 648 to -32 769	-2 147 483 648 to 2 147 483 647
0 to 2 147 483 647	65 536 to 2 147 483 647

The compiler determines the type based on the range of the lowest and highest elements of the enumerator. For example, the following code results in an enumerator type of int:

   enum COLORS
{  green  = -200,
   blue   = 1,
   yellow = 2,
   red    = 60000
};

The following code results in an enumerator type of short:

   enum COLORS
{  green  = -200,
   blue   = 1,
   yellow = 2,
   red    = 3
};