The opposite of promotion, truncation moves a value from a type to a smaller type. In

that case, the compiler just drops the extra bits. It may or may not generate a compile

time warning of the loss of information. Assigning from an integer to a smaller integer

(e.g.. long to int, or int to char) drops the most significant bits. Assigning from a floating point type to an integer drops the fractional part of the number.

 

char ch;

int i;

 

i = 321;

ch = i;     // truncation of an int value to fit in a char

// ch is now 65

 

 

The assignment will drop the upper bits of the int 321. The lower 8 bits of the number

321 represents the number 65 (321 - 256). So the value of ch will be (char)65 which

happens to be 'A'.

 

The assignment of a floating point type to an integer type will drop the fractional part of the number. The following code will set i to the value 3. This happens when assigning a floating point number to an integer or passing a floating point number to a function which

takes an integer.

 

double pi;

int i;

 

pi = 3.14159;

i = pi;     // truncation of a double to fit in an int

// i is now 3

 

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