Module 6 · Ethereum & Shared Applications / 6.12

Follow the whole application.

Connect the record, the program, the market, and the risk.

You have met a lot of pieces. Bring them together around one simple request: someone wants to exchange a token through a website.

The website is the doorway. It is not the whole system.

Trace one action from end to end.

The wallet helps the user authorize a request. A network receives it. The execution rules determine whether it is valid and what the contract does. Consensus coordinates the accepted history.

The contract may use a token allowance, an AMM pool, an outside price feed, or another application. The trade changes inventory, and the transaction consumes work. A successful transaction is evidence of execution, not evidence of a profitable or lawful decision.

If the website disappears, a public record may remain accessible through another interface. If the contract has an administrator, a blockchain base layer does not erase that administrator’s powers. Trace each dependency separately.

Each layer has its own operators, controls, and failure conditions. This simplified view omits the RPC connection.

The interface, program, and shared record answer different questions.

Ask what can change.

The market price can change. A pool’s reserves change when traders act. A liquidity position can become inactive. Fees and rewards can change. A stablecoin can lose its target price.

The protocol’s rules can also change, but through an adoption process. Ethereum’s transition to proof of stake preserved its execution history while changing the consensus mechanism. It did not give validators permission to accept invalid transfers.

A useful explanation identifies both the mechanism and its boundary. You should be able to explain what happens in the ordinary case, then name a condition under which your conclusion no longer holds.

Add token B: 10

A received9.09

Average B per A1.1

Next tiny trade B/A1.21

Fee-free constant product, no intervening trades. Actual swaps include fees and rounding.

Use the reserves to predict a trade before checking the displayed result.

The idea to keep

A token is not its website. A program is not a guarantee. A fee is not a profit. Keep those distinctions as you move into practical decisions.

A moment to try it.

Take your time. Explain the reason, not only the answer.

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Match the question to its main layer.

Who can change this contract’s logic?Is the transfer authorized?Which valid history is accepted?What quote follows from these reserves?

Answers stay in this browser. Use examples only—never enter recovery words, keys, account details, or real balances.

Interactive answer checking needs JavaScript. The questions and explanations remain available here.

Match the question to its main layer.

A single transaction passes through several kinds of rules. Calling it “on-chain” does not answer every layer.

A fee-free pool has 100 A and 100 B. Someone adds 100 B. How much A leaves?

The final B reserve is 200. Keeping x × y = 10,000 leaves 50 A in the pool, so 50 A leaves. Buying a larger amount changes the average quote.

An application offers a stablecoin deposit with rewards. Which is the soundest starting question?

Price backing, income sources, and failure conditions describe the mechanism. A displayed rate alone does not.

Explain the constitution analogy and one limit of it.

Validity rules define permitted actions; consensus procedures coordinate a record under those rules; governance is how people consider and adopt changes. Software execution does not decide legal permission, ethical legitimacy, or what every person must accept.

A game closes and its item token survives. Explain both the benefit and what may still be missing.

The public token record and control can remain available to compatible apps. The game experience, file hosting, legal rights, and acceptance by another developer are separate and may disappear.