QR Code (Quick Response Code)
A QR or Quick Response code is a two-dimensional barcode, used commonly for adding web links to a printed page. When you scan such a QR bar code using a web cam or mobile phone camera, the QR reader application takes you to a website, a YouTube video or some other web content. QR codes are an easy way of sending people to a site without having to type a URL.
(1) Sheet folded twice, making pages one-fourth the size of the original sheet. A quarto makes an 8-page signature. (2) Book made from quarto sheets, traditionally measuring about 9' x 12'.
1/20th of a ream (25 sheets).