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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( "%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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