Binary

Contributors: jimblom

Binary in Programming

At their very lowest-level, binary is what drives all electronics. As such, encountering binary in computer programming is inevitable.

Representing binary values in a program

In Arduino, and most other programming languages, a binary number can be represented by a 0b preceding the binary number. Without that 0b the number will just be a decimal number.

For example, these two numbers in code would produce two very different values:

a = 0b01101010; // Decimal 106
c = 01101010;  // Decimal 1,101,010 - no 0b prefix means decimal

Bitwise operators in programming

Each of the bitwise operators discussed a few pages ago can be performed in a programming language.

AND bitwise operator

To AND two different binary values, use the ampersand, &, operator. For example:

x = 0b10011010 & 0b01000110;
// x would equal 0b00000010

AND’ing a binary value is useful if you need to apply a bit-mask to a value, or check if a specific bit in a binary number is 1.

The AND bitwise operator shouldn’t be confused with the AND conditional operation, which uses the double-ampersand (&&) and produces a true or false based on the input of multiple logic statements.

OR bitwise operator

The OR bitwise operator is the pipe | (shift+\, the key below backspace). For example:

y = 0b10011010 | 0b01000110;
// y would equal 0b11011110

OR’ing a binary value is useful if you want to set one or more bits in a number to be 1.

As with AND, make sure you don’t switch up the OR bitwise operator with the OR conditional operator - the double-pipe (||).

NOT bitwise operator

The bitwise NOT operator is the tilde ~ (shift+`, the key above tab). As an example:

z = ~(0b10100110);
// z would equal 0b01011001

XOR bitwise operator

To XOR two values use the caret (^) between them:

r = 0b10011010 ^ 0b01000110;
// r would equal 0b11011100

XOR is useful for checking if bits are different, because it'll only result in a 1 if it operates on both a 0 or 1.

Shifting left and right

To shift a binary number left or right n bits, use the <<n or >>n operators. A couple examples:

i = 0b10100101 << 4;    // Shift i left 4 bits
// i would equal 0b101001010000
j = 0b10010010 >> 2;    // Shift j right 2 bits
// j would equal 0b00100100

Shift's are an especially efficient way to multiply or divide by powers of two. In the example above, shifting four units to the left multiplies that value by 2⁴ (16). The second example, shifting two bits to the right, would divide that number by 2² (4).

Interested in learning more foundational topics?

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