In this article, we will see the BIT Manipulation Interview Questions and answers.
The process of changing bits or other small amounts of data algorithmically is termed as Bit manipulation. Bit manipulation is required for a variety of computer programming activities, including low-level system management, detection of errors and repair methods, encryption, data compression, and optimization. Modern programming languages enable programmers to work exclusively with abstractions rather than their bits for the majority of other activities. The source code for bit manipulation uses the OR, AND, NOT, XOR, and bit shifts bitwise.
Bit manipulation may occasionally remove or reduce the requirement for a data model loop and lead to multiple speeds owing to the simultaneous processing of bit manipulations, but the code becomes more difficult to create and maintain.
We’ll cover a couple of these intriguing bit manipulation techniques and interview questions in this research:
Q1). What is a bit?
The bit is the binary digit and the smallest data unit in a computer. Binary numbers maybe 0 or 1 exclusively, since they are a 2-base number. This implies we have to write 0101 if we wish to indicate the amount 5 in binary.
An integer variable typically has a limit of 32 bits, which implies it comprises 32 bits with a range of 2 bits — 0 or 1 with 2 options.
Q2). What is a byte?
A byte is composed of eight bits, and its maximum value is 255, which indicates that all bits are set. In a moment, we’ll examine why the maximum value of a byte is 255.
Thus, if all bits are adjusted to 255, my byte would appear as follows:
| 1 Byte ( 8 bits ) | ||||||||||
| Place Value | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | ||
| 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | = | 255 |
Add all those numbers altogether i.e., 1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 = 255.
Q3). What is the Bitwise operation?
Bitwise operators have been used to manipulate data on the bit level, which is sometimes referred to as bit-level programming. It is a quick and straightforward operation that is handled directly by the CPU and is used to modify data for comparisons and computations.
Bitwise operations are usually considerably quicker than division, many times faster than multiply, and sometimes strongly faster than adding on basic low-cost processors.
Q4). Name a few bitwise operations that you are familiar with?
NOT: Intuitive NOT is one of the unary operators that reverses the bits in a number, that is, if the bit is 0, it becomes 1 and vice versa.
AND ( & ): AND operator accept patterns of length two bits. If both bits in the bit patterns’ compared location are 1, the resulting bit pattern has a value of 1, else it has a value of 0.
Alternatively ( | ): As with bitwise AND, bitwise OR is one of the binary operators that works on two-bit patterns of equal length. If both bits in the bit patterns’ compared position are 0, the resulting bit pattern has a value of 0, otherwise, it has a value of 1.
XOR: Bitwise XOR accepts patterns of length two bits. If both bits in the adjacent bit patterns are 0 or 1, the resulting bit pattern has a value of 0, otherwise, it has a value of 1.
The left shift operator is a binary operation that shifts a given number of bits to the left and appends a 0 at the end.
Signed Right Shift ( >> ): The right shift operator is a binary operation that shifts a specified number of bits to the right while preserving the sign (which is the first bit)
Zero Fill Right Shift ( >>> ): Shifts right by introducing zeros from the left, effectively filling up the left bits with 0s.
Q5). What are some of the more practical applications of bitwise operators?
- Multiple Boolean Flags Storage
When dealing with memory-constrained devices, it’s difficult to justify assigning a hundred boolean flags to variables. This is a very inefficient method of storing your flags since Boolean values in C are just one byte long. We do not need a whole byte to hold a single zero or one. The remaining bits will stay 0 throughout. When working with just a few KBs of RAM, you could not afford to waste valuable memory.
- Identifying Odd and Even Quantities
Another trick that bitwise operators may do is to determine if a number is even or odd. Thus, the logic behind!(x&1) is as follows: the binary notation of 1 is 0001 (considering just four bits for simplicity), and the least significant bit has a place value of 1. 2n+1 may be used to represent any odd number. Thus, for odd numbers, the least significant bit is always 1. Thus, when any odd integer is compared to 0001 utilizing the bitwise AND operator, the result bytes will be 0001. Thus, we may verify for even integers by using the logical NOT operator. For odd numbers, just omit the logical NOT and check (x&1).
- Without Using a Third Variable, Swapping Variables
Thus, switching two variables without requiring a third variable is possible without using bitwise operators, but why not, given your familiarity with bitwise operators?
Q6). According to you, what is the significance of bitwise operators?
In the programming of hardware registers in integrated devices, bitwise operations are important. For example, any CPU I’ve ever used includes one or more registers (typically a certain memory location) that regulate whether a break is activated or deactivated. To allow the interrupt process to fire, set the enabled bit for the interrupt type while without changing any of the other bits in the register.
When a break is fired, it usually places a bit in a status register, so a single service procedure can identify the exact cause for the break. Testing the various bits enables quick interrupt source decoding.
The total RAM available for many embedded devices maybe 64, 128, or 256 BYTES, In this context, one byte is often used to store numerous data elements, Boolean flags, and more and then to set and read bit operations.
I have been working for many years on a satellite communication system with a payload of 10.5 bytes. The data must be compacted into the data block without leaving the unused bits between fields to make optimal use of this data packet. This implies that bitwise and shift operators are used extensively to collect the information values and pack them into their payloads.
Q7). What is bit masking?
A bit mask is a binary or bitmap number with the required bit(s) and 0. When you do a bitwise AND, a value with a bitmask, you may test for certain bits.
Q8). How can two integers be swapped without an intermediary variable?
One of the frequent tasks you may do in an interview is to exchange your values without adding a third variable, given two variables.
This problem may be rapidly handled by utilizing the XOR swap method with 3 Bitwise OR operations. The sequencing of these operations is here:
1x = x ^ y;
2y = x ^ y;
3x = x ^ y;
Let’s try swap 2 and 5:
let x = 2 // 0010
let y = 5 // 0101
x = x ^ y; // x is now 7 (0111), y is still 5 (0101)
y = x ^ y; // x is still 7 (0111), y is now 2 (0010),
x = x ^ y; // x becomes 5 (0101), y becomes 2 (0010)
Q9). How can you verify whether an integer is odd or even without division?
It is extremely easy to determine whether or not the given integer is odd or even without the modulus operator. Even instead of using the modulus operator, it is possible to verify an integer whether it is odd or even.
This may be done as follows.
Method 1: A number may be tested whether it is odd or even using a bitwise (&) operator.
Method 2: Multiply the number and divide it by 2. Divide and multiply the number by 2. If the output is the same as the input then it is an even number, otherwise it is an odd number.
Method 3: Switch the temporary variable n times to the variable’s initial value.
If the variable flag returns its original (true) value, n is even. Otherwise, n is false.
Following is the example of checking whether an integer is odd or even using a bitwise operator:
Q10). How to verify whether a positive integer equals to power of 2 but without branching?
In the binary display of any (decimal) power of 2, one bit is set to 1, and all bits are set to 0:
1 binary 10 = decimal 2
2 binary 100 = decimal 4
3 binary 1000 = decimal 8
4 binary 10000000 = decimal 1024
If we remove 1 from any kind of number, we obtain a number where one and zero are reversed. For example, compare Decimal 8 and 7 binary representations:
1Binary1000 = Decimal 8
2Binary 0111 = Decimal 7
If we now apply Bitwise AND to both of these integers, the outcome is zero. This resultant zero guarantees that we have a power of two.
(Remember, that now in parentheses you will not need to provide number – 1, since the subtraction is above Bitwise AND.)
