karnaugh map question

[khatus]

I can't understand how decimal designation differ by power of 2??

[rstofer]

Look closely at the middle map.  Note how the squares are numbered 0..3.  That value is the binary value of the two bits concatenated as A|B.  The upper left square is 00 so the value is 0.  The upper right square is 01 so the value is 1.

Now look at the combined squares 1 and 3.  They differ by a power of 2 and in this  case the power is 1.  2¹ = 2

The left map shows the case where the values vary by 1: squares 0 and 1 differ by 1 or 2⁰.

[Ian.M]

In other words, an over-complicated way of saying they differ by one binary bit . . . . 

That's the trouble with many textbooks where the author was paid by the word! 

[khatus]

Thanks😊