i am guessing you're not from the US, and OOP is. in the US, first of all, a billion is 10^9. secondly, phone numbers here are typically 7 digits, with an additional 3 digit area code tied to a geographical region, the first digit of which can't be a 0.

when i was a kid, before cell phones really took off, it was pretty standard to omit the area code, since we were usually all in the same area code where i lived, but since cell phones have become common, and people are likely to retain their phone numbers when they move, it has become much more typical to include the full ten digits, which would be at least 1.21 billion dollars, by american standards.

[–] Zagorath@aussie.zone 1 points 1 day ago

At least on my part, you guess correctly.

A billion being 10^9^ is, at this point, universal. To my knowledge, only the very old in the UK still hold to the "long billion".

I find that fascinating, because everywhere I've lived (and everywhere I haven't lived but have had reason to be aware of the phone scheme), mobile phone numbers (which often aren't formatted in the same way as landline numbers) are 10 digits and start with a leading zero.

Growing up, landlines usually didn't include area code, and would be 8 digits, starting with a non-zero number. But adding an area code would mean adding 2 digits, the first of which is always 0.

So basically, if I see a phone number without a leading zero, I'm going to be very confused, unless I have reason to believe that it includes country code.

[–] Zwiebel@feddit.org 2 points 1 day ago (2 children)

US cellphone have area codes? Here they have a three digit code as well but it's required and not tied to any area, unlike landline

[–] captain_aggravated@sh.itjust.works 3 points 1 day ago

The US did not create new area codes for cell phones. I kinda wonder if it would have ever worked. There are only like 800 of them available to the whole nation. 000-199 are not usable; neither an area code or an exchange can start with a leading 0 or 1. And certain round numbers and easy to remember area codes like 200, 211, 300, 311 etc. are reserved. 411 for example is the infromation service, 911 is the emergency number. Fun fact: cell phones are required to be able to dial 911 even if they don't have a plan or number associated to them. If you dial 911 from a disconnected cell phone, the system will randomly assign that phone a number with a 911 area code.

Even though you can carry a phone elsewhere with you, they are still "area codes." If you get a new cell phone, it will be assigned an area code for the area you purchased it in. People have moved around and kept their familiar numbers, which is what this XKCD comic is referring to.

The next three digits are the "exchange," which once upon a time was also routable. Everyone in the same town or neighborhood might have the same exchange, so at one point you really only had to remember 4 digits for a particular phone number, because you knew what exchange and area they were in. Especially with cell phones it's pretty much 10 random digits.

[–] juliebean@lemmy.zip 2 points 1 day ago

here, the area code is ostensibly still tied to a geographic area, and it is optional when dialing a number in the same area code, even for cell phones, i believe. when you get a cell phone number the area code is just the area code where you first got the number. so like i live in a college town, and you can fairly reliably tell where somebody is from based on their phone number.