Opcodes

The DSL identifies opcodes by their byte. Scripts use names. Aliases such as cltv/nop2, csv/nop3 and ctv/nop4 are names for the same byte. Each consensus value sets the function of each byte.

In bitcoin

Opcode	Byte	Description
if	0x63	Run the next branch if the top item is true.
notif	0x64	Run the next branch if the top item is false.
else	0x67	Switch to the other branch.
endif	0x68	End a conditional.
verify	0x69	Fail unless the top item is true.
drop	0x75	Remove the top item.
dup	0x76	Duplicate the top item.
swap	0x7c	Swap the top two items.
size	0x82	Push the size of the top item. The item stays on the stack.
equal	0x87	Push true if the top two items are equal, else push false.
equalverify	0x88	Fail unless the top two items are equal.
add	0x93	Replace the top two numbers with their sum.
sha256	0xa8	Replace the top item with its SHA256.
hash160	0xa9	Replace the top item with its HASH160.
checksig	0xac	Check a signature against a pubkey and the sighash.
checksigverify	0xad	CHECKSIG, then fail unless it succeeded.
nop1	0xb0	Does nothing; reserved for soft-fork upgrades.
cltv	0xb1	BIP65: fail unless nLockTime has reached the top item.
csv	0xb2	BIP112: fail unless this input's nSequence encodes at least the top item.
nop4	0xb3	Does nothing; reserved for soft-fork upgrades (BIP119 proposes CTV).
nop5	0xb4	Does nothing; reserved for soft-fork upgrades.
nop6	0xb5	Does nothing; reserved for soft-fork upgrades.
nop7	0xb6	Does nothing; reserved for soft-fork upgrades.
nop8	0xb7	Does nothing; reserved for soft-fork upgrades.
nop9	0xb8	Does nothing; reserved for soft-fork upgrades.
nop10	0xb9	Does nothing; reserved for soft-fork upgrades.

Proposal opcodes

define-consensus can change an upgradable NOP to one of these opcodes.

Opcode	Byte	Description
ctv	0xb3	BIP119 CHECKTEMPLATEVERIFY: fail if the tx that spends the coin does not agree with the template hash on top of the stack.