Question on Bitwise Operators

Question on Bitwise Operators

1. Which of these is not a bitwise operator?

a) &

b) &=

c) |=

d) <=

Answer: d

Explanation: <= is a relational operator.

2. Which operator is used to invert all the digits in a binary representation of a number?

a) ~

b) <<<

c) >>>

d) ^

Answer: a

Explanation: Unary not operator, ~, inverts all of the bits of its operand in binary representation.

3. On applying Left shift operator, <<, on integer bits are lost one they are shifted past which position bit?

a) 1

b) 32

c) 33

d) 31

Answer: d

Explanation: The left shift operator shifts all of the bits in a value to the left specified number of times. For each shift left, the high order bit is shifted out and lost, zero is brought in from the right. When a left shift is applied to an integer operand, bits are lost once they are shifted past the bit position 31.

4. Which right shift operator preserves the sign of the value?

a) <<

b) >>

c) <<=

d) >>=

Answer: b

Explanation: None.

5. Which of these statements are incorrect?

a) The left shift operator, <<, shifts all of the bits in a value to the left specified number of times

b) The right shift operator, >>, shifts all of the bits in a value to the right specified number of times

c) The left shift operator can be used as an alternative to multiplying by 2

d) The right shift operator automatically fills the higher order bits with 0

Answer: d

Explanation: The right shift operator automatically fills the higher order bit with its previous contents each time a shift occurs. This also preserves the sign of the value.

6. What is the output of this program?

    class bitwise_operator

    {

        public static void main(String args[])

        {

            int var1 = 42;

            int var2 = ~var1;

            System.out.print(var1 + " " + var2);    

        }

    }

a) 42 42

b) 43 43

c) 42 -43

d) 42 43

Answer: c

Explanation: Unary not operator, ~, inverts all of the bits of its operand. 42 in binary is 00101010 in using ~ operator on var1 and assigning it to var2 we get inverted value of 42 i:e 11010101 which is -43 in decimal.

output:

$ javac bitwise_operator.java

$ java bitwise_operator

42 -43

7. What is the output of this program?

    class bitwise_operator

    {

        public static void main(String args[])

        {   

             int a = 3;

             int b = 6;

             int c = a | b;

             int d = a & b;            

             System.out.println(c + " "  + d);

        }

    }

a) 7 2

b) 7 7

c) 7 5

d) 5 2

Answer: a

Explanation: And operator produces 1 bit if both operand are 1. Or operator produces 1 bit if any bit of the two operands in 1.

output:

$ javac bitwise_operator.java

$ java bitwise_operator

7 2

8. What is the output of this program?

    class leftshift_operator

    {

        public static void main(String args[])

        {       

             byte x = 64;

             int i;

             byte y;

             i = x << 2;

             y = (byte) (x << 2)

             System.out.print(i + " " + y);

        }

    }

a) 0 64

b) 64 0

c) 0 256

d) 256 0

Answer: d

Explanation: None.

output:

$ javac leftshift_operator.java

$ java leftshift_operator

256 0

9. What is the output of this program?

    class rightshift_operator

    {

        public static void main(String args[])

        {   

             int x;

             x = 10;

             x = x >> 1;

             System.out.println(x);

        }

    }

a) 10

b) 5

c) 2

d) 20

Answer: b

Explanation: Right shift operator, >>, devides the value by 2.

output:

$ javac rightshift_operator.java

$ java rightshift_operator

5

10. What is the output of this program?

    class Output

    {

        public static void main(String args[])

        {   

             int a = 1;

             int b = 2;

             int c = 3;

             a |= 4;

             b >>= 1;

             c <<= 1;

             a ^= c;

             System.out.println(a + " " + b + " " + c);

        }

    }

a) 3 1 6

b) 2 2 3

c) 2 3 4

d) 3 3 6

Answer: a

Explanation: None.

output:

$ javac Output.java

$ java Output

3 1 6