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3. Data Types and Sizes

3.1 Numeric Data Types

C has a small family of datatypes: Numeric (int, float, double), Character (char), and User defined (struct, union)

Numeric Data Types: Depending on the precision and range required, you can use one of the following datatypes.

data type	size (Win7 64bits)	signed	unsigned
char	1	char x; signed char x;	unsigned char x;
short	2	short int x; short y;	unsigned short x; unsigned short int y;
default	4	int x;	unsigned int x;
long	4	long x;	unsigned long x;
float	4	float x;	N/A
double	8	double x;	N/A

The unsigned version has roughly double the range of its signed counterparts.

Signed and unsigned characters differ only when used in arithmetic expressions.

The individual sizes are machine/compiler dependent. However, the following is guaranteed:

sizeof(char)<sizeof(short)<=sizeof(int)<=sizeof(long)

sizeof(char)<sizeof(short)<=sizeof(float)<=sizeof(double)

3.2 Big endian vs. little endian

NUXI problem

– This terminology alludes to the issue that a value represented by the byte-string "UNIX" on a big-
endian system may be stored as "NUXI" on a PDP-11 middle-endian system.
– For numeric data types that span multiple bytes, the order of arrangement of the individual bytes is important.

Depending on the device architecture, we have "big endian" and "little endian" formats.

3.2.1 Big endian

The most significant bits (MSBs) occupy the lower address.