Inside Macintosh: Mac OS Runtime Architectures /

Chapter 4 - PowerPC Runtime Conventions

Data Types

Table 4-1 lists the binary data types and their sizes in the PowerPC runtime environment.

Table 4-1 Data types in the PowerPC runtime environment

Type	Size (bytes)	Alignment (bytes)	Range	Notes
UInt8	1	1	0 to 255
SInt8	1	1	-128 to 127
SInt16	2	2	-32,768 to 32,767
UInt16	2	2	0 to 65,535
SInt32	4	4	-2-31 to 231 -1
UInt32	4	4	0 to 232-1
Boolean	1	1		0 = false, nonzero = true
float	4	4	±(2-149 to 2127)	IEEE 754 standard
double	8	8	±(2-1074 to 21023)	IEEE 754 standard
Pointer	4	4	0 to FFFFFFFF

All numeric and pointer data types are stored in big-endian format (that is, high bytes first, then low bytes). Signed integers use two's-complement representation.

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© Apple Computer, Inc.
11 MARCH 1997