How it works. Please give some example.

Question

Consider the following foo function and identify the return value of foo function.

int foo (unsigned int n)

{

            int c, x = 0;

            while (n! = 0)

            {

                        if (n & 01) x++;

                        n >>= 1;

}

return x;

}

(a) It counts the total number of bits set in an unsigned integer.

(b) It counts the number of bits which are zero.

(c) It counts the number of occurrences of 01.

(d) It returns the same value as ‘n’.

Comments

check the code, c is not used ===> every time it returns 0 only

if you return x, then option A is matching

to understand it, pre-requisite is &, >>= operators working phenomena.

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Oh sorry, i have edited..now ... Explain this

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It will simply count the number of set bits.

Option A is Correct.

Answer 1

say n= 1101

now if n&01 means we will do bitwise and with n and 1.i.e,

1101 & 0001 ..now in this example the unit's place of n has 1 so 1&1 will give 1 here and hence if(1) will be true so we will increment x by 1.

now n>>=1 means n=n>>1 so will do right shift on n until n is completely exhausted i.e, n becomes 0000. so

according to our example,

1st right shift : 0110 & 0001 => 0 as 0&1 is 1=0 so x will remain 1

2nd right shift: 0011 & 0001=> 1 and x is now 2

3rd right shift: 0001 & 0001 =>1 and x is now 3

4th right shift: n becomes 0000 so while(n!=0) condition fails and we exit from the loop..

now x=3 i.e the total no of set bits or 1 in i/p stream so ans is A