Interview Cake
A bit shift moves each digit in a number's binary representation left or right. There are three main types of shifts:
Left Shifts
When shifting left, the most-significant bit is lost, and a 0 bit is inserted on the other end.
The left shift operator is usually written as "<<".
A single left shift multiplies a binary number by 2:
Logical Right Shifts
When shifting right with a logical right shift, the least-significant bit is lost and a 0 is inserted on the other end.
For positive numbers, a single logical right shift divides a number by 2, throwing out any remainders.
Arithmetic Right Shifts
When shifting right with an arithmetic right shift, the least-significant bit is lost and the most-significant bit is copied.
Languages handle arithmetic and logical right shifting in different ways. Java provides two right shift operators: >> does an arithmetic right shift and >>> does a logical right shift.
The first two numbers had a 1 as the most significant bit, so more 1's were inserted during the shift. The last two numbers had a 0 as the most significant bit, so the shift inserted more 0's.
If a number is encoded using two's complement, then an arithmetic right shift preserves the number's sign, while a logical right shift makes the number positive.
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