math or result fault

Projects Programming
1

Hi mu question is very simple .

when i try use bitewise or the result wrong. for example

void setup() {

int result;
delay(50);
result=0x0000 | 0x8000;
delay (500);
Serial.println (result,HEX);

}

result must be 8000 but after running programm result FFFF8000. I mean it add 16 bit more. how can it be. Thanks

2

What happens if "result" is an unsigned int?

(Please rest assured, you haven't added sixteen bits)

3

math or result fault

Nope, Pilot Error.

Since 'result' is an 'int', this:

result=0x0000 | 0x8000;

Produces a negative number on an 8-bit processor (as @AWOL opined). 0x8000 = -32768 (decimal).
When you do:

Serial.println (result,HEX);

The print function casts it as a 'long' which sign extends it to 32 bits: 0xFFFF8000.