# ✨ The EVM ✨
## tl;dr
* EVM is a quasi-Turing complete machine (quasi because computation is intrinsically bounded/limited through a parameter: gas)
* EVM is the runtime environment for smart contracts.
* "Ethereum virtual machine code" or "EVM code" are cute lil code are written in a low-level, stack-based bytecode language, each byte represents an operation.
* EVM memory is a simple stack-based architecture with: stack, volatile memory, non-volatile storage (word size of 256-bit) and the fearful Calldata.
## Opcodes
EVM instruction set can be classified into 11 categories:
* Stop and Arithmetic Operations
* Comparison & Bitwise Logic Operations
* SHA3
* Environmental Information
* Block Information
* Stack, Memory, Storage and Flow Operations
* Push Operations
* Duplication Operations
* Exchange Operations
* Logging Operations
* System Operations
### Stop and Arithmetic Operation
0x00 STOP 0 0 Halts execution
0x01 ADD 2 1 Addition operation
0x02 MUL 2 1 Multiplication operation
0x03 SUB 2 1 Subtraction operation
0x04 DIV 2 1 Integer division operation
0x05 SDIV 2 1 Signed integer division operation (truncated)
0x06 MOD 2 1 Modulo remainder operation
0x07 SMOD 2 1 Signed modulo remainder operation
0x08 ADDMOD 3 1 Modulo addition operation
0x09 MULMOD 3 1 Modulo multiplication operation
0x0a EXP 2 1 Exponential operation
0x0b SIGNEXTEND 2 1 Extend length of two’s complement signed integer
## Comparison & Bitwise Logic Operations
0x10 LT 2 1 Less-than comparison
0x11 GT 2 1 Greater-than comparison
0x12 SLT 2 1 Signed less-than comparison
0x13 SGT 2 1 Signed greater-than comparison
0x14 EQ 2 1 Equality comparison
0x15 ISZERO 1 1 Simple not operator
0x16 AND 2 1 Bitwise AND operation
0x17 OR 2 1 Bitwise OR operation
0x18 XOR 2 1 Bitwise XOR operation
0x19 NOT 1 1 Bitwise NOT operation
0x1a BYTE 2 1 Retrieve single byte from word
0x1b SHL 2 1 Left shift operation
0x1c SHR 2 1 Logical right shift operation
0x1d SAR 2 1 Arithmetic (signed) right shift operation
### Environmental Information
0x30 ADDRESS 0 1 Get address of currently executing account
0x31 BALANCE 1 1 Get balance of the given account
0x32 ORIGIN 0 1 Get execution origination address
0x33 CALLER 0 1 Get caller address
0x34 CALLVALUE 0 1 Get deposited value by the instruction/transaction responsible for this execution
0x35 CALLDATALOAD 1 1 Get input data of current environment
0x36 CALLDATASIZE 0 1 Get size of input data in current environment
0x37 CALLDATACOPY 3 0 Copy input data in current environment to memory
0x38 CODESIZE 0 1 Get size of code running in current environment
0x39 CODECOPY 3 0 Copy code running in current environment to memory
0x3a GASPRICE 0 1 Get price of gas in current environment
0x3b EXTCODESIZE 1 1 Get size of an account’s code
0x3c EXTCODECOPY 4 0 Copy an account’s code to memory
0x3d RETURNDATASIZE 0 1 Get size of output data from the previous call from the current environment
0x3e RETURNDATACOPY 3 0 Copy output data from the previous call to memory
0x3f EXTCODEHASH 1 1 Get hash of an account’s code
### Block Information
0x40 BLOCKHASH 1 1 Get the hash of one of the 256 most recent complete blocks
0x41 COINBASE 0 1 Get the block’s beneficiary address
0x42 TIMESTAMP 0 1 Get the block’s timestamp
0x43 NUMBER 0 1 Get the block’s number
0x44 DIFFICULTY 0 1 Get the block’s difficulty
0x45 GASLIMIT 0 1 Get the block’s gas limit
### Stack, Memory, Storage and Flow Operations
0x50 POP 1 0 Remove item from stack
0x51 MLOAD 1 1 Load word from memory
0x52 MSTORE 2 0 Save word to memory
0x53 MSTORE8 2 0 Save byte to memory
0x54 SLOAD 1 1 Load word from storage
0x55 SSTORE 2 0 Save word to storage
0x56 JUMP 1 0 Alter the program counter
0x57 JUMPI 2 0 Conditionally alter the program counter
0x58 PC 0 1 Get the value of the program counter prior to the increment corresponding to this instruction
0x59 MSIZE 0 1 Get the size of active memory in bytes
0x5a GAS 0 1 Get the amount of available gas, including the corresponding reduction for the cost of this instruction
0x5b JUMPDEST 0 0 Mark a valid destination for jumps. This operation has no effect on machine state during execution.
### Push Operations
0x60 PUSH1 0 1 Place 1 byte item on stack
0x61 PUSH2 0 1 Place 2-byte item on stack
PUSH3, PUSH4, PUSH5…PUSH31 place 3, 4, 5..31 byte items on stack respectively
0x7f PUSH32 0 1 Place 32-byte (full word) item on stack
### Duplication Operations
0x80 DUP1 1 2 Duplicate 1st stack item
DUP2, DUP3..DUP15 duplicate 2nd, 3rd..15th stack item respectively
0x8f DUP16 16 17 Duplicate 16th stack item
### Exchange Operations
0x90 SWAP1 2 2 Exchange 1st and 2nd stack items
0x91 SWAP2 3 3 Exchange 1st and 3rd stack items
SWAP3, SWAP4..SWAP15 exchange 1st and 4th..15th stack items respectively
0x9f SWAP16 17 17 Exchange 1st and 17th stack items
### Logging Operations
0xa0 LOG0 2 0 Append log record with no topics
0xa1 LOG1 3 0 Append log record with one topic
0xa2 LOG2 4 0 Append log record with two topics
0xa3 LOG3 5 0 Append log record with three topics
0xa4 LOG4 6 0 Append log record with four topics
### System Operations
0xf0 CREATE 3 1 Create a new account with associated code
0xf1 CALL 7 1 Message-call into an account
0xf2 CALLCODE 7 1 Message-call into this account with an alternative account’s code
0xf3 RETURN 2 0 Halt execution returning output dat
0xf4 DELEGATECALL 6 1 Message-call into this account with an alternative account’s code, but persisting the current values for sender and value
0xf5 CREATE2 4 1 Create a new account with associated code
0xfa STATICCALL 6 1 Static message-call into an account
0xfd REVERT 2 0 Halt execution reverting state changes but returning data and remaining gas
0xfe INVALID ∅ ∅ Designated invalid instruction
0xff SELFDESTRUCT 1 0 Halt execution and register account for later deletion