Hello, Erop, you wrote: E> it is not assured that it here was, and is not assured that it for programmers. E> but to backs. E> we develop the standard of a QR-code. E> our QR-code of the size NxN is a small square from N x N pixels. Each pixel black or white. E> difficulty consists that when we scan the code, we do not know, what side turns a square. 4 variants (0, 90, 180 and 270 degrees) E> the Question are possible all? How many different unique numbers it is possible to encode such code so, what the read out number did not depend on square orientation. Just in case the comment is a little aside: it is necessary to understand that read process QR can be subject to errors (since the same error of frontier sampling: gray is black or white?) therefore for practical application do not forget about the control of integrity of the data built in a QR-code. Otherwise trash in - trash out.