Typical sizes of basic C data types

Signed	Unsigned	32-bit	64-bit
C declaration	C declaration	Bytes	Bytes
[signed] char	unsigned char	1	1
short	unsigned short	2	2
int	unsigned	4	4
long	unsigned long	4	8
int32_t	uint32_t	4	4
int64_t	uint64_t	8	8
char *		4	8
float		4	4
double		8	8

Observation

• The size of an object changes with the word size of the processor where the program is run.
• Using fixed size integer types like int32_t and int64_t is the best way to have close control over data representation regardless of the processor the compiler is run.

Ranges of various C data types

32-bit programs

64-bit programs

Sources

• Computer Systems - A Programmer’s Perspective

Related Notes

• Encoding unsigned integers as binary
• Encoding signed integers as binary