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<<

[Bitwise Operators]

Description

The left shift operator << causes the bits of the left operand to be shifted left by the number of positions specified by the right operand.

Syntax

variable << number_of_bits;

Parameters

variable: Allowed data types: byte, int, long.
number_of_bits: a number that is < = 32. Allowed data types: int.

Example Code

int a = 5;      // binary: 0000000000000101
int b = a << 3; // binary: 0000000000101000, or 40 in decimal

Notes and Warnings

When you shift a value x by y bits (x << y), the leftmost y bits in x are lost, literally shifted out of existence:

int x = 5;  // binary: 0000000000000101
int y = 14;
int result = x << y;  // binary: 0100000000000000 - the first 1 in 101 was discarded

If you are certain that none of the ones in a value are being shifted into oblivion, a simple way to think of the left-shift operator is that it multiplies the left operand by 2 raised to the right operand power. For example, to generate powers of 2, the following expressions can be employed:

Operation  Result
---------  ------
1 <<  0      1
1 <<  1      2
1 <<  2      4
1 <<  3      8
...
1 <<  8    256
1 <<  9    512
1 << 10   1024
...

The following example can be used to print out the value of a received byte to the serial monitor, using the left shift operator to move along the byte from bottom(LSB) to top (MSB), and print out its Binary value:

// Prints out Binary value (1 or 0) of byte
void printOut1(int c) {
for (int bits = 7; bits > -1; bits--) {
// Compare bits 7-0 in byte
if (c & (1 << bits)) {
Serial.print("1");
}
else {
Serial.print("0");
}
}
}