2.1. Data Types

2.1.1. Scalar Data Types

The table below lists the size and range of each scalar type as supported in the tiarmclang compiler. Many of the minimum and maximum values for each range are available as standard macros in the C standard header file limits.h.

The storage and alignment of data types is described in Object Representation.

Type	Size	Min Value	Max Value
signed char	8 bits	-128	127
char unsigned char bool	8 bits	0	255
short signed short	16 bits	-32768	32767
unsigned short	16 bits	0	65535
int signed int long signed long	32 bits	-2147483648	2147483647
enum	packed	-2147483648	2147483647
unsigned int unsigned long wchar_t	32 bits	0	4294967295
long long signed long long	64 bits	-9223372036854775808	9223372036854775807
unsigned long long	64 bits	0	18446744073709551615
float	32 bits	1.175494e-38	3.40282346e+38
double long double	64 bits	2.22507385e-308	1.79769313e+308
pointers references data member ptrs	32 bits	0	0xFFFFFFFF

Notes:

• The “plain” char type has the same representation as either signed char or unsigned char. The -fsigned-char and -funsigned-char options control whether “plain” char is signed or unsigned. The default is unsigned.

• The wchar_t type has the same representation as unsigned int. The tiarmclang runtime libraries do not support a 16-bit wchar_t type. Attempts to use the tiarmclang -fshort-wchar option may cause issues when linked with the tiarmclang runtime libraries.

• 64-bit data types is aligned on a 64-bit (8-byte) boundary.

• Further discussion about the size of enum types can be found below in the Enum Type Storage.

• Specified minimum values for floating-point types in the table above indicate the smallest precision value > 0.

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

2.1.2. Enum Type Storage

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 the following table:

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 65535	256 to 65535	unsigned short
-128 to 1 -32768 to -129	128 to 32767 -32768 to 32767	signed short
0 to 4294967295	2147483648 to 4294967295	unsigned int
-32768 to -1 -2147483648 to -32769 0 to 2147483647	32767 to 2147483647 -2147483648 to 2147483647 65536 to 2147483647	signed int

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    = 30000
};