ITPEC IP October 2021 Question 73
Which of the following is the coding scheme that can encode a large amount of information into a small area and has an error correction function that enables the code to be read out correctly even when the code cannot be partially read out?
Explanation
QR code — a two-dimensional code that packs a lot of data into a small area and corrects errors, so it can be read even when part of it is dirty or damaged.
A QR code stores data both horizontally and vertically, so a small square holds up to several thousand digits, against a few dozen in a one-dimensional bar code. Reed–Solomon error correction lets a reader restore up to about 30% of a damaged symbol, depending on the correction level chosen, and the three corner finder patterns let it be read from any direction.
Answer (c)
Why not others:
- •(a) ISBN code — an identification number for books; printed as a one-dimensional bar code it holds only a few digits
- •(b) ITF code — Interleaved 2 of 5, a one-dimensional bar code used on shipping cartons; small capacity, and its check digit only detects errors
- •(d) Unicode — a character code set that assigns numbers to the characters of the world's scripts; it is not a printed symbol at all
Key rule: One-dimensional bar codes (JAN, ITF, ISBN) hold a few digits and at most detect errors; two-dimensional codes such as QR hold far more and correct errors.
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