ITPEC IP October 2018 Question 74

Position detection patterns identify the reading direction — the three square finder patterns in its corners let a reader find how a QR code is rotated.

A QR code is a matrix-type two-dimensional code: data is stored in a grid of black and white cells, both horizontally and vertically. The position detection patterns (cut-out symbols) in three corners tell the scanner where the code is and which way it faces, so it can be read at high speed from any angle. It also carries error-correction data, so a partly dirty or damaged code can still be read.

Answer (a)

Why not others:

• •(b) — the opposite: storing data in two directions makes a QR code much smaller than a one-dimensional barcode holding the same data
• •(c) — a QR code stores numbers, alphanumeric characters, binary data and double-byte characters such as kanji and kana, not only numbers and letters
• •(d) — bar codes stacked one above another describe a stacked-type 2D code such as PDF417; a QR code is a single matrix

Key rule: A one-dimensional barcode holds data in one direction and must be scanned across; a matrix code like QR holds data in both directions, stores much more in less space, and reads from any angle.

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