The term altcoin has various similar definitions. Stephanie Yang of The Wall Street Journal defined altcoins as "alternative digital currencies," while Paul Vigna, also of The Wall Street Journal, described altcoins as alternative versions of bitcoin. Aaron Hankins of the MarketWatch refers to any cryptocurrencies other than bitcoin as altcoins.
NEM — Unlike most other cryptocurrencies that utilize a Proof of Work algorithm, it uses Proof of Importance, which requires users to already possess certain amounts of coins in order to be able to get new ones. It encourages users to spend their funds and tracks the transactions to determine how important a particular user is to the overall NEM network.
The idea of not needing a third-party exchange can admittedly be a tempting one, especially if you're worried about how secure they are. But direct trades come with plenty of risks, too. By putting you directly in contact with the buyer, they leave the method of trading up to you, including potential in-person exchanges, which are incredibly risky to do with a stranger. Some of these methods can also be annoying, frustrating and more time-consuming than preferred, and if a buyer is unreliable, it can take even longer should you end up successfully selling them at all.
In Charles Stross' 2013 science fiction novel, Neptune's Brood, the universal interstellar payment system is known as "bitcoin" and operates using cryptography. Stross later blogged that the reference was intentional, saying "I wrote Neptune's Brood in 2011. Bitcoin was obscure back then, and I figured had just enough name recognition to be a useful term for an interstellar currency: it'd clue people in that it was a networked digital currency."
The unit of account of the bitcoin system is a bitcoin. Ticker symbols used to represent bitcoin are BTC[b] and XBT.[c] Its Unicode character is ₿.:2 Small amounts of bitcoin used as alternative units are millibitcoin (mBTC), and satoshi (sat). Named in homage to bitcoin's creator, a satoshi is the smallest amount within bitcoin representing 0.00000001 bitcoins, one hundred millionth of a bitcoin. A millibitcoin equals 0.001 bitcoins, one thousandth of a bitcoin or 100000 satoshis.
Bitcoin owners who use Coinbase as their wallet use Coinbase's own exchange, GDAX, to buy and sell their cryptocurrencies. If you have bitcoins in your Coinbase wallet, GDAX also exchanges Bitcoin Cash, Ethereum, and Litecoin. Go to GDAX and login with your information. At the top of the page click "Select Product" and pick which crypto you want to buy with bitcoin by either choosing BCH/BTC, ETH/BTC, or LTC/BTC. On the left side of the page are the options for Market, Limit, and Stop. Entering the amount of BTC you want to spend for Market and pressing Buy allows for an immediate purchase at current market prices. Limit tries to order at the specified price or better. A Stop order becomes active after a specified price is reached, and you have the option for it to be a market order or limit order.
The receiver of the first bitcoin transaction was cypherpunk Hal Finney, who created the first reusable proof-of-work system (RPOW) in 2004. Finney downloaded the bitcoin software on its release date, and on 12 January 2009 received ten bitcoins from Nakamoto. Other early cypherpunk supporters were creators of bitcoin predecessors: Wei Dai, creator of b-money, and Nick Szabo, creator of bit gold. In 2010, the first known commercial transaction using bitcoin occurred when programmer Laszlo Hanyecz bought two Papa John's pizzas for 10,000 bitcoin.