How hard is the 21 million cap on bitcoin?

[MarpleTrading]

I am wondering how hard is the 21M cap on bitcoin.

Is it juts a define that easily could be changed?

#define MAX_BITCOIN 21000000;

in to

#define MAX_BITCOIN 1000000000;

recompile and now we have a 1 billion cap.


I could of course look in the code, but I think there are people here who already know and it save me time.

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[shawshankinmate37927]

Anyone that modified the code to create additional coins would be creating a fork--a seperate ledger.

[Anon136]

Nothing is stopping you if you wanted to do that but most of us would ignore your alteration so your NewBitCoin probably wouldn't be very valuable.

[LiteCoinGuy]

There are already coins where the limit Is the sky like feathercoin, chinacoin and shitcoin...

[Stephen Gornick]

I could of course look in the code,

The miner's code could be modified to change the rules and grant any number of coins but that block then would be relayed to peers.  Since that change breaks the protocol, peer nodes would reject that block as being invalid and then would not relay it.  

Now if other nodes run the same change and thus accept that block, they will relay it but it still doesn't matter if nobody will buy those mined coins.

So there would be a reason for enough people (an "economic majority") to decide that the change is wanted and to be willing to buy those coins from the miner.

But if you hold bitcoins, you wouldn't want those to be devalued and thus would reject the change.

And if you have borrowed coins and have to repay, and the lender will refuse any coins issued after the change occurred, then you won't buy those coins from the miners either.

So yes ... technically it is as easy as changing one line of code.  But getting the economic majority to accept the change is the hard part (essentially the impossible part, for the change you are suggesting).
 - http://en.bitcoin.it/wiki/Economic_majority

[Birdy]

If you want to know how difficult it is, try imagening this:

There are 1 million people and your task is convincing over 0.5 million of them to take 90% of their dollars and throw them into a big fire.
That's how difficult it is to make this change.
(the dollars in this scenario must still be considered as valuable ;p)

[Paladin69]

If LTC keeps gaining popularity, you can consider it all one big group of 21 million + 84 million.

[AliceWonder]

Can I ask why people are worried about this?

The limit isn't going to be reached for a long time, so it really isn't a concern for us. When block reward becomes really small, then start looking into if it is even an issue, but it isn't going to be an issue for a very long time and when that time comes we'll have a lot more experience to base opinions on.

[DeathAndTaxes]

The limit isn't defined as a number value it is simply the upper limit from the sum of block rewards.
The code defines the block reward as 50 BTC which is halved (technically right shifted) every 210,000 blocks.

You can easily change that.  You could mine a block which has a 50,000,000,000,000,000,000,000,000,000,000 BTC reward today, of course all nodes running the current code will simply reject it as invalid.

[TippingPoint]

How hard is the 21 million cap on bitcoin?

Harder than Chinese arithmetic.

[Lethn]

As people have said, if you just up and change the limit on the amount of overall Bitcoins and think no one will notice think again, so far there have been some relatively minor changes in comparison that have made people rage on these forums before, that's the beauty of open source.

[polarhei]

I am wondering how hard is the 21M cap on bitcoin.

Is it juts a define that easily could be changed?

#define MAX_BITCOIN 21000000;

in to

#define MAX_BITCOIN 1000000000;

recompile and now we have a 1 billion cap.


I could of course look in the code, but I think there are people here who already know and it save me time.

In centralized system or simple programming,  that is simple to do. But in the model of the discussion, The being has at least three methods to prevent the simple modification as if you mod the factor, then the code will need to re-calculate to follow, additionally, there are many copies to ensure the limit cannot be modified even the source code can be read. That is from DSP Concept. So it is impossible to modify the initial number once  You have beamed this out decentralised.

[drawingthesun]

The eventual limit is actually just under 21 million.

See this calculation to get an idea, just keep adding the divide by two on the end:

Code:

(210000*50)+(210000*(50/2))+(210000*(50/2/2))+(210000*(50/2/2/2))+(210000*(50/2/2/2/2))+(210000*(50/2/2/2/2/2))+(210000*(50/2/2/2/2/2/2))+(210000*(50/2/2/2/2/2/2/2))+(210000*(50/2/2/2/2/2/2/2/2))

If you keep adding more and more, it approaches 21 million but never actually touches it.
(reward halves every 210,000 blocks for all time...)


Here is some of the code that determines the reward and thus the final number of coins:

Code:

int64 static GetBlockValue(int nHeight, int64 nFees)
{
    int64 nSubsidy = 50 * COIN;

    // Subsidy is cut in half every 210,000 blocks which will occur approximately every 4 years.
    nSubsidy >>= (nHeight / Params().SubsidyHalvingInterval());

    return nSubsidy + nFees;
}

https://github.com/bitcoin/bitcoin/blob/4ad73c6b080c46808b0c53b62ab6e4074e48dc75/src/main.cpp#L1230

However, the main issue with actually changing these options is that most of the people using Bitcoin have bought into the idea of Bitcoin as it is and they do not want more coins. For Bitcoin to change the vast majority of the users would have to agree. What's more likely is that any change will become yet another fork. There are already many different "Bitcoins" out there, all fighting for their share of the market.

[MarpleTrading]

Can I ask why people are worried about this?

I am not worried about this, just curious. Advocates of BTC always tell you that BTC, unlike fiat, has a cap and that that is why it is a deflationary system instead of a inflationary system by design. 

[westkybitcoins]

Can I ask why people are worried about this?

I am not worried about this, just curious. Advocates of BTC always tell you that BTC, unlike fiat, has a cap and that that is why it is a deflationary system instead of a inflationary system by design. 

Well, that's really the beauty of Bitcoin... not so much that there's a cap, but that the cap is nigh-impossible to overcome.

[kokojie]

If LTC keeps gaining popularity, you can consider it all one big group of 21 million + 84 million.

Unless 1 LTC become exact same value as 1 Bitcoin, I don't see how can it be 21 million + 84 million. Also LTC serves a different purpose.

[Piper67]

If LTC keeps gaining popularity, you can consider it all one big group of 21 million + 84 million.

Unless 1 LTC become exact same value as 1 Bitcoin, I don't see how can it be 21 million + 84 million. Also LTC serves a different purpose.

As long as LTC can be traded independently of BTC (which it can) the first statement is unadulterated rubbish.

[prodigits7]

It's a valid concern but will never happen, the community will not allow it.

[luv2drnkbr]

it's 50%+1 hard.  (it's majorly hard)

[luv2drnkbr]

If LTC keeps gaining popularity, you can consider it all one big group of 21 million + 84 million.

i dont think you understand how markets work... at the most basic level