• Hyperreality
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    1 year ago

    In the Dutch example above, it’s house numbers 2-34 in one particular street.

    Amsterdam, population 1 million, is divided into roughly 100 4 digit postal numbers (1000, 1001, etc.), that’s the same as Budapest and many places.

    But I think at one point they then added on the additional postal code letters (AA, AB, …, ZZ). By adding two letters you can potentially further divide each of the 4 digit postal numbers. 100 x 26 x 26 = 67600 possible postcodes.

    In theory, Budapest could easily transition to that. Everyone keeps their existing 4 digit postal number, just add 2 or 3 letters. I googled and Budapest has 200 postcodes. So 200 x 26 x 26 x 22 = 3.5 million postcodes. No need to write the street, number or town anymore. Just a postal code.

    I don’t know how UK postcodes work, but I think they have an older/mixed system where the city or area is abbreviated. So in the above example for the BBC, the postcode starts with SW because London is in the South West.

    • @[email protected]
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      21 year ago

      On the UK post codes, you’re pretty close to correct.

      In the first part of the code, you’ve got 1-2 letters, which is the postcode area and usually based on a city name (W is West London in the BBC example). After the letters you’ve got 1-2 numbers (or a number followed by a letter, as in W1A). This gives a more granular division of the area, so it’ll often refer to smaller towns.

      The second part is used to narrow it down to a small group of actual addresses, although the number and area it covers varies.

      I went down a bit of a Wikipedia rabbit hole while checking a couple of bits about the format, and learnt that there are actually a few special cases/non-geographic post codes, including the postcode XMA 5HQ, which is specifically for letters to Santa.