What does a bitwise shift left or right do and what is it used for

Question

I ve seen the operators  gt  gt  and  lt  lt  in various code that I ve looked at  none of which I actually understood   but I m just wondering what they actually do and what some practical uses of them are  If the shifts are like x   2 and x   2  what is the real difference from actually using the   and   operators  Is there a performance difference

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The bit shift operators are more efficient as compared to the / or * operators.

In computer architecture, divide(/) or multiply(*) take more than one time unit and register to compute result, while, bit shift operator, is just one one register and one time unit computation.

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Left bit shifting to multiply by any power of two  Right bit shifting to divide by any power of two   x   x  lt  lt  5     Left shift y   y  gt  gt  5     Right shift   In C C   it can be written as    include  lt math h gt   x   x   pow 2  5   y   y   pow 2  5

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Some examples   Bit operations for example converting to and from Base64  which is 6 bits instead of 8  doing power of 2 operations  1  lt  lt  4 equal to 2 4 i e  16  Writing more readable code when working with bits  For example  defining constants using 1  lt  lt  4 or 1  lt  lt  5 is more readable

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Left shift  It is equal to the product of the value which has to be shifted and 2 raised to the power of number of bits to be shifted  Example  1  lt  lt  3 0000 0001  --- gt  1 Shift by 1 bit 0000 0010 ---- gt  2 which is equal to 1 2 1 Shift By 2 bits 0000 0100 ---- gt  4 which is equal to 1 2 2 Shift by 3 bits 0000 1000 ---- gt  8 which is equal to 1 2 3  Right shift  It is equal to quotient of value which has to be shifted by 2 raised to the power of number of bits to be shifted  Example  8  gt  gt  3 0000 1000  --- gt  8 which is equal to 8 2 0 Shift by 1 bit 0000 0100 ---- gt  4 which is equal to 8 2 1 Shift By 2 bits 0000 0010 ---- gt  2 which is equal to 8 2 2 Shift by 3 bits 0000 0001 ---- gt  1 which is equal to 8 2 3

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Left Shift  x   x   2 value  normal operation   x  lt  lt  value   bit-wise operation     x   x   16  which is the same as 2 4   The left shift equivalent would be x   x  lt  lt  4  Right Shift  x   x   2 value  normal arithmetic operation   x  gt  gt  value  bit-wise operation     x   x   8    which is the same as 2 3   The right shift equivalent would be x   x  gt  gt  3

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Left bit shifting to multiply by any power of two and right bit shifting to divide by any power of two  For example  x   x   2  can also be written as x lt  lt 1 or x   x 8 can be written as x lt  lt 3  since 2 to the power of 3 is 8   Similarly x   x   2  is x gt  gt 1 and so on

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Here is an example   include quot stdio h quot   include quot conio h quot   void main         int rm  vivek      clrscr        printf  quot Enter any numbers t E g   1  2  5 quot        scanf  quot  d quot    amp rm      rm   5 0101   lt  lt  2  two step add zero s   so the value is 10100     printf  quot This left shift value d  d quot   rm  rm lt  lt 4       printf  quot This right shift value d  d quot   rm  rm gt  gt 2       getch

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Yes  I think performance-wise you might find a difference as bitwise left and right shift operations can be performed with a complexity of o 1  with a huge data set  For example  calculating the power of 2   n  int value   1  while  exponent lt n                  Print out current power of 2         value   value  2     Equivalent machine level left shift bit wise operation         exponent                      Similar code with a bitwise left shift operation would be like  value   1  lt  lt  n   Moreover  performing a bit-wise operation is like exacting a replica of user level mathematical operations  which is the final machine level instructions processed by the microcontroller and processor

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Here is an applet where you can exercise some bit-operations  including shifting  You have a collection of bits  and you move some of them beyond their bounds  1111 1110  lt  lt  2 1111 1000  It is filled from the right with fresh zeros     0001 1111  gt  gt  3 0000 0011  Filled from the left  A special case is the leading 1  It often indicates a negative value - depending on the language and datatype  So often it is wanted  that if you shift right  the first bit stays as it is  1100 1100  gt  gt  1 1110 0110  And it is conserved over multiple shifts  1100 1100  gt  gt  2 1111 0011  If you don t want the first bit to be preserved  you use  in Java  Scala  C    C as far as I know  and maybe more  a triple-sign-operator  1100 1100  gt  gt  gt  1 0110 0110  There isn t any equivalent in the other direction  because it doesn t make any sense - maybe in your very special context  but not in general  Mathematically  a left-shift is a   2  2 left-shifts is a   4 and so on  A right-shift is a    2 and so on

[bit-manipulation] What does a bitwise shift (left or right) do and what is it used for?

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