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Dear All,
can anybody help me to following doubts i am thankful to you
1.2.Code:#include<stdio.h> void main() { int a=3; printf("%d", ~a); } It showing -4 how come?Code:#include<stdio.h> void main() { union { unsigned i1:8; unsigned i2:8; unsigned i3:8; unsigned i4:8; }uu; uu. i1=257; printf("\n %d::%d" ,sizeof(uu), uu.i2); } it showing 4 ,1 answer how come? also if i print any of uu.i1, uu.i2, uu.i3 all showing 1 only please help me?
What value do you EXPECT for ~3? Do you understand what ~3 means?
Do you understand how unions work? Do you understand how bitfields work? In your case, you have a bitfield that is 8 bits wide. What does that mean for a value of 257?
--
Mats
Compilers can produce warnings - make the compiler programmers happy: Use them!
Please don't PM me for help - and no, I don't do help over instant messengers.
hai Mats..Originally Posted by matsp
thanks for your reply.... ~3 means 2's complement of 3 right? Can u explain me that union example so that i wil understand...i am new to programming thats y i am asking you silly questions
It starts to fall apart with the void main (main returns int).
> Can u explain me that union example so that i wil understand
It's the same reason that (for 8-bit chars)
unsigned char c = 257;
performs modulo 256 on the value to make it fit in the space available.
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
Yes, but what does 2's complement actually achieve - or put another way, what do you find strange or don't understand about the result -4.
As to unions, perhaps you would look that up in your C book?
--
Mats
Compilers can produce warnings - make the compiler programmers happy: Use them!
Please don't PM me for help - and no, I don't do help over instant messengers.
