astronomy

Universal Product Code

Universal Product Code is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Universal Product Code rather than just read about it. In short: The Universal Product Code (UPC or UPC code) is a barcode symbology that is used worldwide for tracking trade items in stores. The chosen symbology has bars (or spaces) of exactly 1, 2, 3, or 4 units wide each; each decimal digit to be encoded consists of two bars and two spaces chosen to have a total width of 7 units, in both an "even" and an "odd" parity form, which enables being scanned in either direction.

Key takeaways

Universal Product Code belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Universal Product Code to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Universal Product Code from memory before moving on to harder problems.

Reference excerpt

The Universal Product Code (UPC or UPC code) is a barcode symbology that is used worldwide for tracking trade items in stores. The chosen symbology has bars (or spaces) of exactly 1, 2, 3, or 4 units wide each; each decimal digit to be encoded consists of two bars and two spaces chosen to have a total width of 7 units, in both an "even" and an "odd" parity form, which enables being scanned in either direction. Special "guard patterns" (3 or 5 units wide, not encoding a digit) are intermixed to help decoding. A UPC (technically, a UPC-A) consists of 12 digits that are uniquely assigned to each trade item. The international GS1 organisation assigns the digits used for both the UPC and the related International Article Number (EAN) barcode. UPC data structures are a component of Global Trade Item Numbers (GTINs) and follow the global GS1 specification, which is based on international standards. Some retailers, such as clothing and furniture, do not use the GS1 system, instead using other barcode symbologies or article number systems. Some retailers use the EAN/UPC barcode symbology, but do not use a GTIN for products sold only in their own stores. Research indicates that the adoption and diffusion of the UPC stimulated innovation and contributed to the growth of international retail supply chains.

History

In 1973, a group of trade associations from the grocery industry formed the Uniform Product Code Council (UPCC) which, with the help of consultants Larry Russell and Tom Wilson of McKinsey & Company, defined the numerical format that formed the basis of the Uniform Product Code. Technology firms including Charegon, IBM, Litton-Zellweger, Pitney Bowes-Alpex, Plessey-Anker, RCA, Scanner Inc., Singer, and Dymo Industries/Data General, put forward alternative proposals for symbol representations to the council. The Symbol Selection Committee finally chose to implement the IBM proposal designed by George J. Laurer in the North Carolina Research Triangle Park but with a slight modification to the font in the human readable area. The first UPC-marked item ever to be scanned at a retail checkout was a 10-pack (50 sticks) of Wrigley's Juicy Fruit chewing gum, purchased at the Marsh supermarket in Troy, Ohio, at 8:01 a.m. on 26 June 1974. The NCR cash register rang up 67 cents. The shopping cart also contained other barcoded items but the gum was the first one picked up at the checkout. A facsimile of the gum packet went on display at the Smithsonian Institution's American history museum in Washington, D.C. Murray Eden was a consultant on the team that created the Universal Product Code barcode. As chairman of a committee of scientists at the Massachusetts Institute of Technology, he helped "select a symbol that would endure the inevitable rush of technology that lay ahead." He chose the font, and he came up with the idea to add numbers to the bottom, which is a fail-safe system, in case the barcode reader is not working correctly.

IBM proposal Around late 1969, IBM at Research Triangle Park (RTP) in North Carolina assigned George Laurer to determine how to make a supermarket scanner and label. In late 1970, Heard Baumeister provided equations to calculate characters-per-inch achievable by two IBM bar codes, Delta A and Delta B. In February 1971, Baumeister joined Laurer. Delta B compared bar widths to space width to code bits. This was extremely sensitive to ink spread, where improper levels of ink or pressure would cause both edges of a bar to spread outward or shrink in. In mid 1971, William "Bill" Crouse invented a new bar code called Delta C. It achieved four times the characters per inch as Delta B. Delta C achieved its higher performance by only using leading to leading or trailing to trailing edges which was unaffected by uniform ink spread. The code provided best performance when it had a defined character set with a fixed reference distance that spanned most or preferably all the character. In August 1971, Crouse joined the scanner effort. After several months they had made no progress. They were aware of the RCA bull's eye label that could be scanned with a simple straight line laser scanner, but a readable label was far too large. Although Litton Industries proposed a bull's eye symbol cut in half to reduce the area, it was still too large and presented the same ink smear printing problems as the RCA symbol. The redundancy and checking ability were removed completely. They were also aware of the many proposals from around the world, none of which were feasible.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Universal Product Code

Start with the simplest possible case. Write down what Universal Product Code claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Universal Product Code before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Universal Product Code ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Universal Product Code

In research: Universal Product Code appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Universal Product Code in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Universal Product Code is common in secondary-school and first-year university syllabi. It links to neighbouring topics 20th-century inventions, American inventions, Barcodes, so understanding it makes those chapters shorter.
In everyday life: Look for Universal Product Code outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Universal Product Code in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Universal Product Code means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Universal Product Code out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Universal Product Code in simple terms?

Why does Universal Product Code matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Universal Product Code?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Universal Product Code.