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XPM is a peer-to-peer open source cryptocurrency that implements a unique scientific computing proof-of-work system. Primecoin has been described [ by whom? When comparing Primecoin with today's most widely spread cryptocurrency called bitcoin some notable differences are:. Primecoin uses the finding of prime chains composed of Cunningham chains and bi-twin chains for proof-of-work, which can lead to useful byproducts.
The system is designed so that the work is efficiently verifiable by all nodes on the Primecoin network. Other cryptocurrencies including bitcoin commonly use a Hashcash type of proof-of-work based on SHA hash calculations, which are of no value beyond its own economy. List of largest known Cunningham chains of given length [13] includes several results generated by Primecoin miners.
Currency symbol — A currency symbol is a graphic symbol used as a shorthand for a currencys name, especially in reference to amounts of money. Many currencies in the English-speaking world and Latin America, place it before the amount, the Cape Verdean escudo places its symbol in the decimal separator position.
The usage of many European countries, such as France, Germany, the decimal separator also follows local countries standards. For instance, the United Kingdom often uses an interpunct as the point on price stickers. Commas or decimal points are common separators used in other countries, see decimal separator for information on international standards.
Older currency symbols have evolved slowly, often from previous currencies, the dollar and peso symbols originated from the mark employed to denote the Spanish real de a ocho, whereas the pound and lira symbols evolved from an L standing for libra, a Roman pound of silver. Newly invented currencies and currencies adopting new symbols have symbolism closer to their adopter, the added center bar in the real sign is meant to symbolize stability.
There are also considerations, such as the perception of the business community. For a new symbol to be used, software to render it needs to be promulgated, the EU was criticized for not considering how the euro symbol would need to be customized to work in different fonts. The original design was exceptionally wide. These two factors have led to most typefaces employing customized, font-specific versions, usually with reduced width, List of currencies List of circulating currencies Currency Symbols.
Central bank — A central bank, reserve bank, or monetary authority is an institution that manages a states currency, money supply, and interest rates. Central banks also usually oversee the commercial banking system of their respective countries, Central banks in most developed nations are institutionally designed to be independent from political interference.
Still, limited control by the executive and legislative bodies usually exists, prior to the 17th century most money was commodity money, typically gold or silver. However, promises to pay were widely circulated and accepted as value at least five hundred years earlier in both Europe and Asia. The Song dynasty was the first to issue generally circulating paper currency, in , in an effort to control inflation, the succeeding Ming Dynasty ended the use of paper money and closed much of Chinese trade.
The Bank of Amsterdam, established in the Dutch Republic in , is considered to be the forerunner to modern central banks.
The Wisselbanks innovations helped lay the foundations for the birth and development of the banking system that now plays a vital role in the worlds economy. Along with a number of local banks, it performed many functions of a central banking system. Lucien Gillard calls it the European guilder, and Adam Smith devotes many pages to explaining how the bank guilder works, the model of the Wisselbank as a state bank was adapted throughout Europe, including the Bank of Sweden and the Bank of England.
Established by Dutch-Latvian Johan Palmstruch in , Sveriges Riksbank is often considered by many as the worlds oldest central bank, the lenders would give the government cash and also issue notes against the government bonds, which could be lent again. A Royal Charter was granted on 27 July through the passage of the Tonnage Act , the bank was given exclusive possession of the governments balances, and was the only limited-liability corporation allowed to issue banknotes.
The currency crisis of , caused by panicked depositors withdrawing from the Bank led to the government suspending convertibility of notes into specie payment. The bank was accused by the bullionists of causing the exchange rate to fall from over issuing banknotes. Nevertheless, it was clear that the Bank was being treated as an organ of the state, henry Thornton, a merchant banker and monetary theorist has been described as the father of the modern central bank.
An opponent of the real bills doctrine, he was a defender of the bullionist position, thorntons process of monetary expansion anticipated the theories of Knut Wicksell regarding the cumulative process which restates the Quantity Theory in a theoretically coherent form.
Until the mid-nineteenth century, commercial banks were able to issue their own banknotes, many consider the origins of the central bank to lie with the passage of the Bank Charter Act of Peer-to-peer — Peer-to-peer computing or networking is a distributed application architecture that partitions tasks or workloads between peers.
Peers are equally privileged, equipotent participants in the application and they are said to form a peer-to-peer network of nodes. Peers are both suppliers and consumers of resources, in contrast to the traditional client-server model in which the consumption, while P2P systems had previously been used in many application domains, the architecture was popularized by the file sharing system Napster, originally released in The concept has inspired new structures and philosophies in many areas of human interaction, in such social contexts, peer-to-peer as a meme refers to the egalitarian social networking that has emerged throughout society, enabled by Internet technologies in general.
While P2P systems had previously used in many application domains. The peer-to-peer movement allowed millions of Internet users to directly, forming groups and collaborating to become user-created search engines, virtual supercomputers.
The basic concept of peer-to-peer computing was envisioned in earlier systems and networking discussions, reaching back to principles stated in the first Request for Comments.
The early Internet was more open than present day, where two machines connected to the Internet could send packets to each other without firewalls and other security measures and this contrasts to the broadcasting-like structure of the web as it has developed over the years.
As a precursor to the Internet, ARPANET was a successful client-server network where every participating node could request, however, ARPANET was not self-organized, and it lacked the ability to provide any means for context or content-based routing beyond simple address-based routing. Therefore, a messaging system that is often likened as an early peer-to-peer architecture was established.
USENET was developed in and is a system that enforces a decentralized model of control, the basic model is a client-server model from the user or client perspective that offers a self-organizing approach to newsgroup servers.
However, news servers communicate with one another as peers to propagate Usenet news articles over the group of network servers. In May , with more people on the Internet, Shawn Fanning introduced the music. A peer-to-peer network is designed around the notion of equal peer nodes simultaneously functioning as both clients and servers to the nodes on the network. This model of network arrangement differs from the model where communication is usually to.
Overlays are used for indexing and peer discovery, and make the P2P system independent from the network topology. Based on how the nodes are linked to each other within the overlay network, unstructured peer-to-peer networks do not impose a particular structure on the overlay network by design, but rather are formed by nodes that randomly form connections to each other.
Communications protocol — These are the rules or standard that defines the syntax, semantics and synchronization of communication and possible error recovery methods. Protocols may be implemented by hardware, software, or a combination of both, Communicating systems use well-defined formats for exchanging various messages. Each message has a meaning intended to elicit a response from a range of possible responses pre-determined for that particular situation. The specified behavior is independent of how it is to be implemented.
Communications protocols have to be agreed upon by the parties involved, to reach agreement, a protocol may be developed into a technical standard. Multiple protocols often describe different aspects of a single communication, a group of protocols designed to work together are known as a protocol suite, when implemented in software they are a protocol stack.
As the PSTN and Internet converge, the two sets of standards are also being driven towards convergence, the nature of a communication, the actual data exchanged and any state-dependent behaviors, is defined by these specifications. In digital computing systems, the rules can be expressed by algorithms, expressing the algorithms in a portable programming language makes the protocol software operating-system independent.
Operating systems usually contain a set of cooperating processes that manipulate shared data to communicate each other. This communication is governed by protocols, which can be embedded in the process code itself. In contrast, because there is no memory, communicating systems have to communicate with each other using a shared transmission medium. Transmission is not necessarily reliable, and individual systems may use different hardware or operating systems, to implement a networking protocol, the protocol software modules are interfaced with a framework implemented on the machines operating system.
This framework implements the functionality of the operating system. Systems typically do not use a protocol to handle a transmission. Instead they use a set of cooperating protocols, sometimes called a family or protocol suite.
Open-source model — Open-source software may be developed in a collaborative public manner. In the early days of computing, programmers and developers shared software in order to learn from each other, eventually the open source notion moved to the way side of commercialization of software in the years Netscapes act prompted Raymond and others to look into how to bring the Free Software Foundations free software ideas, the new term they chose was open source, which was soon adopted by Bruce Perens, publisher Tim OReilly, Linus Torvalds, and others.
The Open Source Initiative was founded in February to encourage use of the new term, a Microsoft executive publicly stated in that open source is an intellectual property destroyer. I cant imagine something that could be worse than this for the software business, IBM, Oracle, Google and State Farm are just a few of the companies with a serious public stake in todays competitive open-source market.
There has been a significant shift in the corporate philosophy concerning the development of FOSS, the free software movement was launched in In , a group of individuals advocated that the free software should be replaced by open-source software as an expression which is less ambiguous. Software developers may want to publish their software with an open-source license, the Open Source Definition, notably, presents an open-source philosophy, and further defines the terms of usage, modification and redistribution of open-source software.
Software licenses grant rights to users which would otherwise be reserved by law to the copyright holder. Several open-source software licenses have qualified within the boundaries of the Open Source Definition, the open source label came out of a strategy session held on April 7, in Palo Alto in reaction to Netscapes January announcement of a source code release for Navigator.
They used the opportunity before the release of Navigators source code to clarify a potential confusion caused by the ambiguity of the free in English.
Many people claimed that the birth of the Internet, since , started the open source movement, the Free Software Foundation, started in , intended the word free to mean freedom to distribute and not freedom from cost.
Since a great deal of free software already was free of charge, such software became associated with zero cost. The Open Source Initiative was formed in February by Eric Raymond and they sought to bring a higher profile to the practical benefits of freely available source code, and they wanted to bring major software businesses and other high-tech industries into open source.
Perens attempted to open source as a service mark for the OSI. The Open Source Initiatives definition is recognized by governments internationally as the standard or de facto definition, OSI uses The Open Source Definition to determine whether it considers a software license open source.
Proof-of-work system — The concept may have been first presented by Cynthia Dwork and Moni Naor in a journal article. The term Proof of Work or POW was first coined and formalized in a paper by Markus Jakobsson, a key feature of these schemes is their asymmetry, the work must be moderately hard on the requester side but easy to check for the service provider.
This idea is known as a CPU cost function, client puzzle. Proof of bandwidth approaches have been discussed in the context of cryptocurrency, Proof of ownership aims at proving that specific data are held by the prover.
One popular system—used in bitcoin mining and Hashcash— uses partial hash inversions to prove that work was done, as a good-will token to send an e-mail. For instance the following header represents about hash computations to send a message to calvin comics.
Proof-of-work systems are being used as a primitive by other more complex systems such as bitcoin which uses a system similar to Hashcash. There are two classes of proof-of-work protocols, challenge-response protocols assume a direct interactive link between the requester and the provider.
The provider chooses a challenge, say an item in a set with a property, the requester finds the relevant response in the set, as the challenge is chosen on the spot by the provider, its difficulty can be adapted to its current load.
The work on the side may be bounded if the challenge-response protocol has a known solution. Most such schemes are unbounded probabilistic iterative procedures such as Hashcash, a generic technique for reducing variance is to use multiple independent sub-challenges, as the average of multiple samples will have lower variance. There are also fixed-cost functions such as the time-lock puzzle, memory-bound where the computation speed is bound by main memory accesses, the performance of which is expected to be less sensitive to hardware evolution.
Network-bound if the client must perform few computations, but must collect some tokens from remote servers before querying the final service provider, in this sense the work is not actually performed by the requester, but it incurs delays anyway because of the latency to get the required tokens. Finally, some POW systems offer shortcut computations that allow participants who know a secret, typically a private key, the rationale is that mailing-list holders may generate stamps for every recipient without incurring a high cost.
Whether such a feature is desirable depends on the usage scenario, the idea of making proofs-of-work reusable for some practical purpose had already been established in Prime number — A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. A natural number greater than 1 that is not a number is called a composite number.