Data Storage Formats

This section describes the storage formats of the data types available in the Cx51 compiler. The Cx51 compiler offers a number of basic data types to use in your C programs. The following table lists these data types along with their size requirements and value ranges.

Data Type	Bits	Bytes	Value Range
Bit	1	—	0 to 1
signed char	8	1	-128 to +127
unsigned char	8	1	0 to 255
Enum	8 / 16	1 or 2	-128 to +127 or -32768 to +32767
signed short	16	2	-32768 to +32767
unsigned short	16	2	0 to 65535
signed int	16	2	-32768 to +32767
unsigned int	16	2	0 to 65535
signed long	32	4	-2147483648 to 2147483647
unsigned long	32	4	0 to 4294967295
Float	32	4	±1.175494E-38 to ±3.402823E+38
data , idata , pdata *	8	1	0x00 to 0xFF
code, xdata	16	2	0x0000 to 0xFFFF
generic pointer	24	3	Memory type (1 byte); Offset (2 bytes) 0 to 0xFFFF

Other data types, like structures and unions, may contain scalars from this table. All elements of these data types are allocated sequentially and are byte-aligned due to the 8-bit architecture of the 8051 family.