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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

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