In the last couple of months, I've been seeing the ú symbol on British receipts. Why?
1963 - ASCII
In the beginning* was ASCII. A standard way for computers to exchange text. ASCII was originally designed with 7 bits - that means 128 possible symbols. That ought to be enough for everyone, right?
Wrong! ASCII is the American Code for Information Interchange. It contains a
$ symbol, but nothing for other currencies. That's a problem because we don't all speak American.
*ASCII has its origins in the telegraph codes of the early 20th Century. They derive from Baudot codes from the 19th Century.
1981 - Extended ASCII
So ASCII gradually morphed into an 8 bit language - and that's where the problems began. Symbols 0-127 had already been standardised and accepted. What about symbols 128 - 255?
Because of the vast range of symbols needed for worldwide communication - and only 256 symbols available in an 8 bit language - computers began to rely on "code pages". The idea is simple, the start of a file contains a code to say what language the document is written in. The computer uses that to determine which set of symbols to use.
Each human script / alphabet needed its own code page. For example Greek uses 737 and Cyrillic uses 855. This means that the same code can be rendered multiple different ways depending on which encoding is used.
Here's how symbols 162, 163, and 164 are rendered in various code pages.
|Code Page 437 (Latin US)||ó||ú||ñ|
|Code Page 737 (Greek)||λ||μ||ν|
|Code Page 855 (Cyrillic)||б||Б||ц|
|Code Page 667 (Polish)||ó||Ó||ñ|
|Code Page 720 (Arabic)||ت||ث||ج|
|Code Page 863 (French)||ó||ú||¨|
As you can see, characters are displayed depending on which encoding you use. If the computer gets the encoding wrong, your text will become incomprehensible mix of various languages.
This made everyone who worked with computers very angry.
1983 - DEC
This is silly! You can't have the same code representing different symbols. That's too confusing. So, in 1983, DEC introduced yet another encoding standard - the Multinational Character Set.
On the DEC VT100, the British Keyboard Selection has the
£ symbol in position 35 of extended ASCII (35 + 128 = 163). This becomes important later.
Of course, if you sent text from a DEC to an IBM, it would still get garbled unless you knew exactly what encoding was being used.
People got even angrier.
Eventually, ISO published 8859-1 - commonly known as Latin-1.
It takes most of the previous standards and juggles them around a bit, to put them in a somewhat logical order. Here's a snippet of how it compares to code page 437.
|Code Page 437 (Latin US)||ó||ú||ñ|
8859-1 defines the first 256 symbols and declares that there shall be no deviation from that. Microsoft then immediately deviates with their Windows 1252 encoding.
Everyone hates Microsoft.
1991 - Unicode!
In the early 1990s, Unicode was born out of the earlier Universal Coded Character Set. It attempts to create a standard way to encode all human text. In order to maintain backwards compatibility with existing documents, the first 256 characters of Unicode are identical to ISO 8859-1 (Latin 1).
A new era of peace and prosperity was ushered in. Everyone now uses Unicode. Nation shall speak peace unto Nation!
2017 - Why hasn't this been sorted out yet?
Here's what's happening. I think.
- The restaurateur uses their till and types up the price list.
- The till uses Unicode and the
£symbol is stored as number
- The till connects to a printer.
- The till sends text to the printer as a series of 8 bit codes.
- The printer doesn't know which code page to use, so makes a best guess.
- The printer's manufacturer decided to fall back to the lowest common denominator - code page 437.
163is translated to
- The customer gets confused and writes a blog post.
Over 30 years later and a modern receipt printer is still using IBM's code page 437! It just refuses to die!
Even today, on modern windows machines, typing
alt+163 will default to 437 and print
As I tap my modern Android phone on the contactless credit card reader, and as bits fly through the air like færies doing my bidding, the whole of our modern world is still underpinned by an ancient and decrepit standard which occasionally pokes its head out of the woodwork just to let us know it is still lurking.
It's turtles all the way down!
— Skylar MacDonald (@helloiamskylar) June 4, 2017
Or is it?
Of course, when we look at the full receipt, we notice something weird.
£ is printed just fine on some parts of the receipt!
⨈Һ𝘢ʈ ╤ћᘓ 𝔽ᵁʗꗪ❓