What is bit manipulation?
Bit manipulation usually refers to changing data using bit operators.
I think Wikipedia expains it good enough so I won't write another article.
https://en.wikipedia.org/wiki/Bit_manipulation
Bit manipulation is the act of algorithmically manipulating bits or
other pieces of data shorter than a word. Computer programming tasks
that require bit manipulation include low-level device control, error
detection and correction algorithms, data compression, encryption
algorithms, and optimization. For most other tasks, modern programming
languages allow the programmer to work directly with abstractions
instead of bits that represent those abstractions. Source code that
does bit manipulation makes use of the bitwise operations: AND, OR,
XOR, NOT, and possibly other operations analogous to the boolean
operators; there are also bit shifts and operations to count ones and
zeros, find high and low one or zero, set, reset and test bits,
extract and insert fields, mask and zero fields, gather and scatter
bits to and from specified bit positions or fields. Integer arithmetic
operators can also effect bit-operations in conjunction with the other
operators.
Bit manipulation, in some cases, can obviate or reduce the need to
loop over a data structure and can give many-fold speed ups, as bit
manipulations are processed in parallel.
Why we need to use bit manipulation?
Because it is fast and often we don't have another choice. For example in microcontrollers, pretty much everything is controlled by manipulating the bits of 8 bit registers. So an output would go high if you set a certain bit 1.
Bit packing is a compression technique that tries to minimize the number of bits necessary to represent a number. While you'll use bit operators to implement it, it is not the same as "bit-manipulation". It's just one of many many use cases for bit-manipulation.
Can anyone show me a simple problem which can be solved using bit manipulation?
Let's say you have a rgb touple rgb = 0xa1fc03 and you want to make the green channel 0.
rgb_without_green = rgb & 0xFF00FF
We've bitwise ANDed the value with 0xFF00FF.
Now rgb is 0xa10003.
Basically any operation boils down to bit manipulation. For most of them you just have convenient solutions. Say instead of 0x00000011 << 0x0000101 you write 3 * 32
Or have a look at this where the addition of two integers is implemented using bit operations. Add two integers using only bitwise operators?
Edit due to comment
How bitwise AND operation between 0xa1fc03 and 0xFF00FF gives 0xa10003
? Just I need to see how to do this calculation
Bitwise AND means that you AND all the bits of both numbers.
1 AND 1 -> 1
0 AND 1 -> 0
1 AND 0 -> 0
0 AND 0 -> 0
So
0xa1fc03 -> 0b101000011111110000000011
0xff00ff -> 0b111111110000000011111111
AND -> 0b101000010000000000000011
0b101000010000000000000011 -> 0xa10003
With a bit more expierience you know that 0xFF is 0b11111111 so you instantly know that 0xa1fc03 AND 0xff00ff is 0xa1003 becaue you keep everything that is masked with FF and set everything 0 that is masked with 00.
There are countless resources available. You should not have to ask me how to bitwise AND two numbers. Please do your own research.
