Bit Twiddling

Front 1

What is the range of short?

Back 1

-32,768 to +32,767

Front 2

Given a bit called A, what is the effect of A ^ 0

Back 2

The result is A

Front 3

How do you toggle a bit in a bitfield

Back 3

bitfield ^ bit

Front 4

How many bytes in a long?

Back 4

4

Front 5

How do you change the sign of a signed integer using bitwise operations?

Back 5

bitwise-not the value and add 1

Front 6

What is the range of unsigned short?

Back 6

0 to 65,535

Front 7

How do you express the value of a bit b in exponential notation

Back 7

2^(b-1)

Front 8

What's an easy way to compute the maximum positive value of an int with bitwise operators?

Back 8

(unsigned int)~0 >> 1

Front 9

Given an integer x, how can you tell if it is a power of 2 using bitwise operators?

Back 9

!((x-1) & x)

Front 10

How many bytes in a short?

Back 10

2

Front 11

How many bytes in an int?

Back 11

4

Front 12

What is the range of char?

Back 12

-128 to +127

Front 13

What is the range of unsigned char?

Back 13

0 to 255

Front 14

What is the range of int? (approx ok)

Back 14

-2,147,483,648 to +2,147,483,647

Front 15

What is the range of unsigned int? (approx ok)

Back 15

0 to 4,294,967,295

Front 16

What is unsigned short max expressed as hex?

Back 16

0xFFFF

Front 17

What is unsigned int max expressed as hex?

Back 17

0xFFFFFFFF

Front 18

How is the most significant bit of a int expressed in exponential notation?

Back 18

2^31

Front 19

How many bytes is a bool?

Back 19

1

Front 20

What is the character for bitwise NOT

Back 20

~

Front 21

What is the character for bitwise OR

Back 21

|

Front 22

What is the character for bitwise XOR

Back 22

^

Front 23

What is the bitwise operator for bitwise AND

Back 23

&

Front 24

What arithmetic operation is the equivalent of the left-shift operator (i.e. <<)

Back 24

Multiplying by two to the power of

Front 25

What arithmetic operation is the equivalent of the right-shift operator (i.e. >>)

Back 25

Dividing by two to the power of

Front 26

How to you clear a bit in a bitfield

Back 26

bitfield & ~bit

Front 27

Given a bit called A, what is the effect of A ^ 1

Back 27

The result is the A flipped

Front 28

Given an ingeger x, how to you find it's twos-complement using bitwise operators?

Back 28

~x + 1

Front 29

Implement the bitarray getter function given the following function signature:

bool getbit(char bitarray[], int bit)

Back 29

bool getbit(char bitarray[], int bit)
{
bitarray += bit / 8;
return *bitarray & (1 << bit % 8);
}

Front 30

Implement a bitarray setter function given the following signature:

void setbit(char bitarray[], int bit, bool value)

Back 30

void setbit(char bitarray[], int bit, bool value)
{
bitarray += bit / 8;
if(value)
{
*bitarray |= (1 << bit % 8);
}
else
{
*bitarray &= ~(1 << bit % 8);
}
}