data types

Question

what is the output of the following programming????

and am confusing is unsigned int stores signed integer, and 

what is ‘ ~ ’ this symbol ?? and what happened when assigning ‘~0’ to y????? and 

what will be printed when x,y are printing and how …?

can anyone tell me how it happened ..Thankyou…..!

#include<stdio.h> int  main() {    unsigned int x = -1;    int y = ~0;    if (x == y)       printf("same");    else       printf("not same"); printf("\n x is %u, y is %u", x, y);    return 0; }

Answer 1

1) When you assign the sign bit to unsigned bit then first converted to 2s complement

-1 => 1| 1 where first 1 is sign and second represent value

Now applying sign bit extension rule so 1111...1 upto the size/capacity of x

2) y=~0 means flip bits and represent in 2s complement i.e -(0+1) = -1

3) x==y then from y=-1 it is converted to unsigned which is 1111.1 upto the size/capacity of y which is same as size taken by x

Hence x and y contains same value

so same is printed

And output in 64 bit compiler is 4294967295 4294967295 here also converting signed to unsigned for y

Comments

nice explanation.....,but am not understanding how 2's complement of 0 will -1. i think 2's complement of 0 is again 0.

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https://stackoverflow.com/questions/791328/how-does-the-bitwise-complement-operator-tilde-work

read this how '~' working

Conclusion for ~ is that

~N = -(N+1)

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okay thank you.......!