Bitshift and bitwise OR operators

Next, "|" is the bitwise OR operator.

When you add the "=" operator, you have this compound operator: "|=".

This is the bitwise inclusive OR with assignment operator.

In the example code, it works as shorthand for "val |= 1".

The full hand notation would be "val = val | 1". It is similar to the way that the expression "val += 1" is short for "val = val + 1".

Here's an example:

If val is "0001000", then "val | 1" would be “0001001” (since 1 = 0000001).

Therefore, "val |= 1" would result to val containing the value "0001001”. Perhaps this make more sense if we arrange the OR calculation like this:

val    0 0 0 1 0 0 0
 1     0 0 0 0 0 0 1
      ---------------
val    0 0 0 1 0 0 1

In binary OR, 1|1 = 1, 1|0 = 1, 0|1 = 1, and 0|0=0.

When the function starts execution, val is initialized to 0. Inside the "for" loop, the first time that the bitshift operator is called has no effect on the value of val. Bitshifting "0000000" will still give you "0000000".

But lets say that arr[0] = 1.

When the sketch hits the next line, "if (arr[i]) val |= 1;", then val will become "0000001".

And when the block loops back to the "for" instruction in line 4, and the bitshift operation is executed again ("val <<= 1;"), then val will become "0000010".

And so on.

See how essentially the contents of the arr array are copied into the val byte variable, one bit at a time?