Question

Hi guys, please help me. i dont know how to do these two questions. In need to get it done .Appreciate if you all could help me and explain it to me( if possible)

1)Assuming flags = 0xAA, what is the value of flags after the following statement is executed? cout << (flags << 2);

Answer: a)0xA8
b)0x54
c)0xAA
d)AA2

2)Which of the following statements will display "Problem!" if bit 2 of flags is a '0'?

Answer : a)if ((flags & 0x04) == 0x04) cout << "Problem!";
b)if ((flags & 0x04) != 0x04) cout << "Problem!";
c)if ((flags ^ 0x04) == 0x04) cout << "Problem!";
d)if ((flags ^ 0x04) != 0x04) cout << "Problem!";

Answer 1

Answer on question #45131 - Programming - C++

1) Assuming flags = 0xAA, what is the value of flags after the following statement is executed? cout << (flags << 2);

Answer:

a) 0xA8

b) 0x54

c) 0xAA

d) AA2

Solution

"<<" is a bitwise operator. It shifts each bit of the value to the left, blank spaces are filled with zeroes.

So we need to convert "flags" variable to binary system.

$$(0xAA)_{16} = (1010\ 1010)_2$$

If we shift all the bits to the left by 2 positions, we will get the following:

$$(1010\ 1010)_2 << 2 = (1010\ 1000)_2$$

Convert it to hexadecimal number system:

$$(1010\ 1000)_2 = (0xA8)_{16}$$

Answer: a)

2) Which of the following statements will display "Problem!" if bit 2 of flags is a '0'?

Answer:

a) if ((flags & 0x04) == 0x04) cout << "Problem!";

b) if ((flags & 0x04) != 0x04) cout << "Problem!";

c) if ((flags ^ 0x04) == 0x04) cout << "Problem!";

d) if ((flags ^ 0x04) != 0x04) cout << "Problem!";

Solution

Convert 0x04 to binary system:

$$(0x04)_{16} = (100)_2$$

We can see, that second bit of this number is 1. Also we know, that second bit of "flags" variable is zero. It means, that if we use & operator, our result will always be 0 (because 1 & 0 = 0 and our number has only one non-zero bit). So, 0 != 0x04. And this result doesn't depend on other bits of "flags" variable.

Answer: b)

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