Bitcoin Forum

As a play on the ridiculousness of the legal age to drink alcohol being 21

Why not 1 bitcoin…

Why not 1million or 100million bitcoins, why not 21 billion, or trillion?

Why not 14 million?

How did other coins like doge and NXT .ect work out there total coins?

Why not 1 bitcoin…

Why not 1million or 100million bitcoins, why not 21 billion, or trillion?

Why not 14 million?

Satoshi wanted Bitcoin to be rare, it's as if he knew the price boom would happen.

The answer to the universe and everything is 42.
Since we are human, imperfect, and not God, and only know half of everything, we should use half of 42.
Therefore, 21 million coins represents that half of the great work is done.  ;)

21 million was not chosen, 21 million is the result of multiple other choices.

Initial block reward was 50BTC
1 block is made every 10 minutes
Block reward halves every 4 years

Those three choices lead to 21 million coins, after so many halvings the block reward eventually hits 0 and at that time the number of coins generated happens to be just under 21 million.

if you look into the source code, 21m was hardcoded, not derived as you have mentioned

Only thing that's hardcoded is:

1. the initial 50 BTC per block
2. reward halving every 210000 blocks

Just these two factors implicitly determine the 21M limit (or actually: 20999999.9769 BTC).

if you look into the source code, 21m was hardcoded, not derived as you have mentioned

CAmount GetBlockValue(int nHeight, const CAmount& nFees)
{
    CAmount nSubsidy = 50 * COIN;
    int halvings = nHeight / Params().SubsidyHalvingInterval();
    // Force block reward to zero when right shift is undefined.
    if (halvings >= 64)
        return nFees;
    // Subsidy is cut in half every 210,000 blocks which will occur approximately every 4 years.
    nSubsidy >>= halvings;
    return nSubsidy + nFees;
}

21 million was the intended number, it isn't "derived" in the sense that it's an arbitrary number.  It was coded intentionally to produce 21 million.

Really?

Did you have a conversation with Mr. Nakamoto whereby he explained this to you?

Ray Dillenger recalls:

I remember this discussion, actually.

Finney, Satoshi, and I discussed how divisible a Bitcoin ought to be.  Satoshi had already more or less decided on a 50-coin per block payout with halving every so often to add up to a 21M coin supply.  Finney made the point that people should never need any currency division smaller than a US penny, and then somebody (I forget who) consulted some oracle somewhere like maybe Wikipedia and figured out what the entire world’s M1 money supply at that time was.

We debated for a while about which measure of money Bitcoin most closely approximated; but M2, M3, and so on are all for debt-based currencies, so I agreed with Finney that M1 was probably the best measure.

21Million, times 10^8 subdivisions, meant that even if the whole word’s money supply were replaced by the 21 million bitcoins the smallest unit (we weren’t calling them Satoshis yet)  would still be worth a bit less than a penny, so no matter what happened — even if the entire economy of planet earth were measured in Bitcoin — it would never inconvenience people by being too large a unit for convenience.

https://thewealthofchips.wordpress.com/2014/10/01/why-bitcoin-is-and-isnt-ideal-money/

I think asking this kind of questions is like asking “Why did you wear green clothes today?”. Yes, there was a decision to be made, but not a very deep one, to be honest.

No, Hal Finney and Ray Dillenger did.



Danny Hamilton, you're not smart enough or important enough to back up how much of an asshole you are.  Maybe take it down a few notches, especially when you're wrong and making a fool of yourself.

Satoshi had already more or less decided on a 50-coin per block payout with halving every so often

A 32bit signed integer can represent numbers from −2,147,483,648 to 2,147,483,647

if you wanted to do accounting for modern currencies with pure integers due to denomination factor of 100 (1$ = 100 cents)
then the obvious choice is to work in cents
Code:

       1 -> 1 cent
     100 -> 1 $

in such a system the most you can represent is slight above 21 million $
Code:

   from  −21,474,836.48 $      to       21,474,836.47 $

Note that left of side of the dot there are 8 digit/decimal places (21 xxx xxx).
Lets assume 1BTC worth(represents) 1 $.
To make it symmetric the dynamic logarithmic range has to be [ 10E-8 , 10E8 ]
This range permits exponential growth or decay for 2*8 orders of magnitude!

I'll try not to be such an asshole in the future, but for some reason my patience always seems to run out when I'm dealing with you.

So that if all gold speculation goes to Bitcoin (at the prices of 2009) the price of bitcoin would be 1000000$ :P

In a slightly earlier version of Satoshi's code (pre-genesis) the limit was 20 million bitcoins.  Blocks were set to arrive every 15 minutes with an initial subsidy of 100 BTC set to halve every 100`000 blocks (about 2 years and 10 months).

Certainly there was some thought put into the magnitude of the limit.  While Satoshi had 63-bits of space to play with (using signed 64-bit integers at the time) it seems possible that he intentionally confined bitcoin amounts to well within 53-bits so that amounts could be handled comfortably by the IEEE 754 binary64 (https://en.wikipedia.org/wiki/IEEE_floating_point#Basic_and_interchange_formats) datatype (potentially useful for JSON-RPC).

What we can be reasonably sure of is that the particular figure of 21 million arose simply as part of some last-minute tweaking and carries no deeper meaning.

21 million was not chosen, 21 million is the result of multiple other choices.

Initial block reward was 50BTC
1 block is made every 10 minutes
Block reward halves every 4 years

Those three choices lead to 21 million coins, after so many halvings the block reward eventually hits 0 and at that time the number of coins generated happens to be just under 21 million.

Legal drinking age is 18 in many European countries.

The answer to the universe and everything is 42.

In a slightly earlier version of Satoshi's code (pre-genesis) the limit was 20 million bitcoins.  Blocks were set to arrive every 15 minutes with an initial subsidy of 100 BTC set to halve every 100`000 blocks (about 2 years and 10 months).

Certainly there was some thought put into the magnitude of the limit.  While Satoshi had 63-bits of space to play with (using signed 64-bit integers at the time) it seems possible that he intentionally confined bitcoin amounts to well within 53-bits so that amounts could be handled comfortably by the IEEE 754 binary64 (https://en.wikipedia.org/wiki/IEEE_floating_point#Basic_and_interchange_formats) datatype (potentially useful for JSON-RPC).

What we can be reasonably sure of is that the particular figure of 21 million arose simply as part of some last-minute tweaking and carries no deeper meaning.

Total number of bitcoins to ever exist is 20999999.97690000, a little less than 21 million. :)

Interesting - where is this code available to support your claim (not that I don't believe you, but I'd like to see it).

I'm surprised I didn't provide a link to begin with.  I must have been in a hurry.

Cryddit posted the source of an alpha snapshot of the reference client here (https://bitcointalk.org/index.php?topic=382374).  Search the page for "GetNextWorkRequired".  You should find all the information you're looking for within this function.

Please let me know if you end up with different numbers.  I routinely screw up idle calculations.