Gavin Wood's introduction to Ethereum and contract programming, given at Assembly 2014, Helsinki, Finland. https://www.youtube.com/watch?v=xO1AxsYAkU8

1. ethereum
Coding society

2. ethereum
Internet is to communication
as
Ethereum is to agreements

3. basic premise
Place & run code in a decentralised singleton isolated
machine;
code can call into other people’s code on the machine;
all transactions with the machine are crypto-signed and
archived;
state fully deterministic.

4. blockchain
Diffuse Singleton Data-Structure
(non-localised, no-authority, no-centre)

5. bitcoin & crypto-currencies
Used blockchain to implement basic
clearing house ‘contract’

6. ethereum & crypto-law
Uses blockchain to implement basic
arbitrary contracts

7. ethereum
Ethereum is to Bitcoin
as
the iPhone is to a calculator

8. ethereum
100% Free software, open development
github.com/ethereum
C++, Go, Python implementations
(Java & Javascript, too)

9. ethereum
State of Ethereum is just the state of a number
of accounts.

10. state: accounts
Address
(160-bit excerpt from the 256-bit public key)
Balance, Nonce[, Code, Storage]
(latter two non-null if a ‘contract’)

11. transactions: state alteration
Alter state by introducing transactions:
either send a message call
or
create a contract.

12. contract creation
endowment (ETH), init code
gas, signature

13. on creation
Places a new account in the system with code
(code in account is whatever is returned from
the init routine)

14. message calls
recipient, value (ETH), data
gas, signature

15. on message receipt
value is transferred to recipient’s balance;
recipient’s code (if any) runs.

16. code execution: virtual machine
Arbitrary size stack
PUSH, POP, SWAP, DUP
Arbitrary temp memory (2256 bytes
addressable)
MLOAD, MSTORE
Code stored in virtual ROM
CODESIZE, CODECOPY

17. virtual machine
Arithmetic/Logic & Crypto
ADD, EXP, EQ, AND, LT, BYTE, SHA3 &c
Flow control
JUMP, JUMPI, PC

18. vm: environment
Can read message input data
CALLDATALOAD, CALLDATASIZE, CALLDATACOPY
Can halt & give message output data
RETURN, STOP, SUICIDE

19. vm: environment
Arbitrary storage (2256 words addressable)
ISOLATED FROM OTHER ACCOUNTS
SLOAD, SSTORE
Can create & send messages.
CREATE, CALL

20. vm: environment
Can query blockchain information
TIMESTAMP, PREVHASH, NUMBER, COINBASE, &c.
Other information
ADDRESS, BALANCE, ORIGIN, CALLER

21. vm
Storage, memory & processing costs ETH
(actually, costs GAS but
GAS ⇔ ETH)

22. lll: basics
expression := ( <op-code> [<operand> ...] )
<operand> is just expression
0 -> PUSH 0
(mload 0x20) -> PUSH 0x20 MLOAD

23. contract: currency
(sstore (caller) 0x1000000000000)
(returnlll (when (= (calldatasize) 64) (seq
(mstore 0 (sload (caller)))
(when (>= (mload 0) (calldataload 32)) (seq
(sstore (caller) (sub (mload 0) (calldataload 32)))
(sstore (calldataload 0)
(add (sload (calldataload 0)) (calldataload 32)))
))
)))

24. lll: advanced
variables: (set ‘name <expression>)
(mload x) / (mstore y z): @x / [y] z
(sload x) / (store y z): @@x / [[y]] z
(calldataload x): $x

25. contract: currency
[[ (caller) ]] 0x1000000000000
(returnlll (when (= (calldatasize) 64) {
(set ‘a @@(caller))
(when (>= @a $32) {
[[(caller)]] (- @a $32)
[[$0]] (+ @@ $0 $32)
})
}))

26. transaction: transfer
to: <currency-contract>
data: <recipient’s-address> <amount-to-transfer>

27. lll: advanced
variadic arithmetic/logic
macros: (def ‘sqr (x) (* x x)) (sqr 4): (* 4 4)

28. lll: name registration
(def ‘registrar
0x50441127ea5b9dfd835a9aba4e1dc9c1257b58ca)
[0] 'register
[32] 'Exchange
(call (- (gas) 21) registrar 0 0 64 0 0)

29. exchange walkthrough...

30. thanks
Looking for devs, too...
C++ in Berlin especially!