Module 6 · Ethereum & Shared Applications / 6.2
A shared machine for agreements.
Why Ethereum added programs to the public record.
Picture a vending machine with a clear rule: insert the right payment, choose a drink, receive the drink. The machine follows a small program.
Now imagine people could inspect that program, and many independent computers could check that it was followed. The rule would no longer live only inside one machine owned by one shop.
That is a useful starting picture for Ethereum. It is not a promise that every program will be fair.
One platform, many programs.
Vitalik Buterin proposed Ethereum in 2013. The idea was a blockchain that developers could use for many applications, rather than designing a separate chain for each new set of rules.
Bitcoin already supports conditions such as requiring several signatures or waiting until a certain time. Ethereum took a different approach: a general-purpose execution environment for programs and their changing records.
“World computer” describes this shared execution. It does not mean one giant laptop, unlimited computing power, or a machine that should replace ordinary servers. Repeating and verifying work across a network is expensive.
The important choice is which rules and records benefit from shared verification. A token transfer may benefit. Rendering every frame of a video game usually would not.
Every copy starts at five. This is a simplified deterministic state update.
A little founding history
Buterin had written about Bitcoin and co-founded Bitcoin Magazine before proposing Ethereum at nineteen. A broader founding team included people who later built other projects. The Ethereum Foundation became part of the ecosystem’s coordination, not an owner with a master switch over every participant.
The 2014 ether sale helped fund development. Ethereum’s public network launched on July 30, 2015. The project developed through contributions from a wider founding team and community.
The program is the agreement you actually run.
A program stored at a blockchain address is called a smart contract. It can hold assets and update records when a transaction calls its functions. The name does not mean it is intelligent or necessarily a legal contract.
Imagine a shared ticket machine. A transaction asks it to issue a ticket. The code checks the payment, updates the available tickets, and assigns the ticket to an account. Nodes verify the resulting change.
The program does not know what the buyer hoped the rules meant. A coding mistake can make it accept something the author never intended. That is still a security failure, not proof that the action was ethical or legally permitted.
Some contracts have fixed logic. Others include pause controls or use an upgrade mechanism that lets an authorized party replace part of the logic. Read the actual control structure. “Smart contract” alone tells you neither “unchangeable” nor “safe.”
A simplified contract with one rule: a valid payment can purchase an available ticket.
A meter stops endless work.
Anyone able to submit transactions could otherwise ask the shared machine to repeat work forever. Ethereum measures computation with gas. Each operation consumes a defined amount of this work budget.
A transaction supplies a limit. If execution runs out, its state changes are reverted, while the computation already performed still costs a fee. This bounds the work a transaction can demand.
Gas is a measure of work. The fee is what that work costs at the applicable gas price. The next lesson separates those two numbers.
A contract can also place limits on an automated assistant, such as which actions it can request. Those protections are only as good as the code, its upgrade permissions, and the transactions you authorize. The machine narrows a task; it does not eliminate every form of trust.
The idea to keep
Ethereum adds shared programs to shared records. It can reduce reliance on one operator for execution, while introducing code, permission, and network risks of its own.