Sync blockchain

1. At the top of Ethereum is DAPP. It exchanges with the smart contract layer through Web3. JS. All smart contracts run on EVM (Ethereum virtual machine) and use RPC calls. Below EVM and RPC are the four core contents of Ethereum, including: blockchain, consensus algorithm, mining and network layer. Except DAPP, all other parts are in the Ethereum client. The most popular Ethereum client is geth (go Ethereum)

2. In recent years, more and more people travel abroad. A good credit card can add a lot to your journey. Everbright Bank is in love with the rhythm of tourism, and has launched a variety of tourism rights cards. Take this Everbright Caesar tourism platinum card as an example. There are many preferential rights and interests. The card and the first brush gift are very generous. Is it really that amazing? Follow Xiaobian to find out
Everbright Caesar travel white card gift
time: before June 30, 2018
Object: Everbright Caesar joint platinum MasterCard customers
ring the activity, customers who activate their credit cards and brush Everbright Caesar joint platinum MasterCard for the first time can enjoy 16 days of free overseas WiFi rights
you need to send self recording videos overseas, so you don't have to worry about non flow money anymore! It should be noted that each customer can only enjoy the right once a month, and only the top 300 customers can enjoy the right once a month
Everbright Caesar travel white card gift
event time: before June 30, 2018
event object: Everbright Caesar joint platinum card MasterCard customer
as long as Everbright Caesar joint platinum card MasterCard customer, ring the event period, the first brush and single currency transaction over $500 or more, you can get the value of 500 yuan of Jingdong e card rights
at the end of the next month after card consumption, the equity password of JD e card will be sent to your mobile phone in the form of SMS, regardless of name, no loss reporting, no cash exchange, and need to be kept properly
here is an introction to the opening ceremony and the first brush ceremony of Everbright Kaiser travel white. Of course, there are a lot of exclusive activities and services, such as Jingdong Mall's card consumption of 300 minus 100, the one-way airport shuttle service of 2 times / year, etc
recently, China Everbright Bank and Caesar tourism released their first joint brand card "Everbright Bank Caesar tourism platinum joint brand credit card" in Beijing. It is reported that the card is the highest level tourism exclusive card launched by both sides and is expected to cover millions of middle-class people in China
the Everbright Bank Kaiser Travel Co branded card launched this time is a platinum grade credit card, which is divided into UnionPay card and MasterCard. The design elements are mainly Aurora, and the design concept comes from "the world shines for me" - boundless dream. As long as you dare to pursue and set out, the world will shine for you
in addition to the basic rights and interests of Everbright, UnionPay and MasterCard platinum cards, the co branded card can also enjoy more exclusive rights and interests. For example, if a new user activates free international WiFi for 16 days, he or she can get the first swipe gift (if he or she swipes the card for more than $500, he or she will get the benefit of Jingdong e-card of $500). He or she can also enjoy airport shuttle, airport VIP hall, air delay insurance, travel accident insurance, road rescue, etc
What's more attractive is that cardholders can enjoy 5 times of points by consuming the whole line of Caesar procts, and they can grab 300 yuan of Caesar travel limited exclusive travel voucher by 1 yuan; Designated overseas cooperative merchants can enjoy 88% discount for consumption by card and customized tourism procts; You can also enter the aurora card zone of Caesar's official website and app as a privilege to purchase the specified preferential routes covering 100 countries and regions around the world, and over 10000 kinds of wonderful tourism procts will be put into the aurora card zone
Liu Yuxiao, general manager of Credit Card Center of China Everbright Bank, said: "this cooperation has effectively integrated the high-quality resources of both sides, and will provide cardholders with better daily travel services and the most convenient payment experience. This is an important step taken by Everbright credit card and Kaiser tourism in improving the quality and efficiency of serving the real economy, supporting the development of Inclusive Finance, and boosting the expansion of domestic demand. ".

3. Enterprise cloud disk, also known as the company's network disk, depends on the company's use scenarios. For example, whether it is just sharing collaborative office, or whether it needs other management or security requirements, such as whether it is necessary to protect documents against leakage, whether it is necessary to protect documents against damage and loss, and whether it can protect against blackmail virus, etc; At the same time, different companies or departments of different companies have different requirements for document management and security. How to make it easy to use, and how to make it compatible with various document types and protect the unity of document security, all these determine what company cloud disk you consider to choose. After all, on the basis of simple document sharing, each proct has different functions, For example, Nanjing Xinlang cloud can flexibly select the corresponding functions according to the needs and concerns of customers. This kind of prevention is targeted, rather than simply saying that the good and bad, appropriate, easy-to-use, stable and cost-effective enterprise cloud disk is good
most of the cloud disks in the market can meet the requirements of document sharing management and mobile office; In addition to the common office office office documents, it is also necessary to conct centralized security control and sharing for the complex drawing documents of the technology R & D department, protect the documents from leakage and proliferation, support online editing of engineering drawing documents, and realize the requirements of the application scenario through the enterprise sharing network disk of Nanjing diamond Information Security Cloud procts.

4. It means that your wallet is consistent with all the blockchains on the Internet. It takes a long time for bitcoin wallet to synchronize and takes up a lot of hard disk

5. In solidness, a contract consists of a set of code (contract function) and data (contract state). The contract is located at a special address on the Ethereum blockchain. uint storedData; This line of code declares a state variable, named storeddata, of type uint (256 bits unsigned integer). You can think of it as a storage unit in a database. Just like managing a database, you can query and modify it by calling functions. In Ethereum, usually only the owner of the contract can do so. In this example, the functions set and get are used to modify and query the values of variables, respectively

like many other languages, when accessing state variables, it is not necessary to add a prefix such as this

this contract can't do a lot (limited by Ethereum's infrastructure), it just allows anyone to store a number. And anyone in the world can access this number. There is no reliable way to protect the number you publish. Anyone can call the set method to set a different number to cover your published number. But your numbers will remain in the history of blockchain. Later we'll learn how to add an access limit so that only you can change the number

token example

the next contract will implement a cryptocurrency in the simplest form. Taking money in the air is no longer a magic trick. Of course, only the person who creates the contract can do it (it's also very easy to use other currency issuance modes, just to realize the differences in details). And anyone can send money to others, without registering a user name and password, as long as there is a pair of Ethereum public and private keys

note
this is not a good example for online solidness environments. If you use the online solidity environment to try this example. The address of from cannot be changed when the function is called. So you can only play the role of a coiner, you can cast money and send it to others, but you can't play the role of others. This online solidity environment will be improved in the future.