Conversions from Signed Integral Types 

When a signed integer is converted to an unsigned integer with equal or greater size and the value of the signed integer is not negative, the value is unchanged. The conversion is made by sign-extending the signed integer. A signed integer is converted to a shorter signed integer by truncating the high-order bits. The result is interpreted as an unsigned value, as shown in this example.   

int i = -3;
unsigned short u;

u = i; 
printf_s( "%hu\n", u );  // Prints 65533 

No information is lost when a signed integer is converted to a floating value, except that some precision may be lost when a long int or unsigned long int value is converted to a float value.

The following table summarizes conversions from signed integral types. This table assumes that the char type is signed by default. If you use a compile-time option to change the default for the char type to unsigned, the conversions given in the Conversions from Unsigned Integral Types table for the unsigned char type apply instead of the conversions in the following table, Conversions from Signed Integral Types.

Conversions from Signed Integral Types

From	To	Method
char1	short	Sign-extend
char	long	Sign-extend
char	unsigned char	Preserve pattern; high-order bit loses function as sign bit
char	unsigned short	Sign-extend to short; convert short to unsigned short
char	unsigned long	Sign-extend to long; convert long to unsigned long
char	float	Sign-extend to long; convert long to float
char	double	Sign-extend to long; convert long to double
char	long double	Sign-extend to long; convert long to double
short	char	Preserve low-order byte
short	long	Sign-extend
short	unsigned char	Preserve low-order byte
short	unsigned short	Preserve bit pattern; high-order bit loses function as sign bit
short	unsigned long	Sign-extend to long; convert long to unsigned long
short	float	Sign-extend to long; convert long to float
short	double	Sign-extend to long; convert long to double
short	long double	Sign-extend to long; convert long to double
long	char	Preserve low-order byte
long	short	Preserve low-order word
long	unsigned char	Preserve low-order byte
long	unsigned short	Preserve low-order word
long	unsigned long	Preserve bit pattern; high-order bit loses function as sign bit
long	float	Represent as float. If long cannot be represented exactly, some precision is lost.
long	double	Represent as double. If long cannot be represented exactly as a double, some precision is lost.
long	long double	Represent as double. If long cannot be represented exactly as a double, some precision is lost.

1. All char entries assume that the char type is signed by default.

Microsoft Specific

For the Microsoft 32-bit C compiler, an integer is equivalent to a long. Conversion of an int value proceeds the same as for a long.

END Microsoft Specific

See Also

Concepts

Assignment Conversions