tech wiki

CTR | Click-through Rate =>

The CTR for an ad is defined as the number of clicks on an ad divided by the number of times the ad is shown (impressions), expressed as a percentage.

The average click-through rate of 3% in the 1990s declined to 0.28% by 2003.

 

QR code | Quick Response code =>

Created by Toyota subsidiary Denso Wave in 1994. It was designed to allow its contents to be decoded at high speed.

Structure of a QR code, highlighting functional elements

宏观结构图。图中颜色是为了显示方便而加的，实际中的QR code只有黑白两色（也没有灰色）。3个角落中的“回”字形方格是供解码软件定位用的。

The diagram below illustrates the placement of the message characters within a QR code. Starting from the lower-right corner, the first four bits define the encoding used (in this case, 8 bits per character). Next is the length of the message (17; dark stands for 1, but the masking process used in this symbol inverts alternate rows). Following that is the message itself, then the end-of-message marker, and finally the error-correcting codes.