Mastering Bitcoin

Appendix A. Transaction Script Language Operators, Constants, and Symbols

Table A-1 shows operators for pushing values onto the stack.

Table A-1. Push value onto stack

Symbol	Value (hex)	Description
OP_0 or OP_FALSE	0x00	An empty array is pushed onto the stack
1-75	0x01-0x4b	Push the next N bytes onto the stack, where N is 1 to 75 bytes
OP_PUSHDATA1	0x4c	The next script byte contains N, push the following N bytes onto the stack
OP_PUSHDATA2	0x4d	The next two script bytes contain N, push the following N bytes onto the stack
OP_PUSHDATA4	0x4e	The next four script bytes contain N, push the following N bytes onto the stack
OP_1NEGATE	0x4f	Push the value “–1” onto the stack
OP_RESERVED	0x50	Halt - Invalid transaction unless found in an unexecuted OP_IF clause
OP_1 or OP_TRUE	0x51	Push the value “1” onto the stack
OP_2 to OP_16	0x52 to 0x60	For OP_N, push the value “N” onto the stack. E.g., OP_2 pushes “2”

Table A-2 shows conditional flow control operators.

Table A-2. Conditional flow control

Symbol	Value (hex)	Description
OP_NOP	0x61	Do nothing
OP_VER	0x62	Halt - Invalid transaction unless found in an unexecuted OP_IF clause
OP_IF	0x63	Execute the statements following if top of stack is not 0
OP_NOTIF	0x64	Execute the statements following if top of stack is 0
OP_VERIF	0x65	Halt - Invalid transaction
OP_VERNOTIF	0x66	Halt - Invalid transaction
OP_ELSE	0x67	Execute only if the previous statements were not executed
OP_ENDIF	0x68	End the OP_IF, OP_NOTIF, OP_ELSE block
OP_VERIFY	0x69	Check the top of the stack, halt and invalidate transaction if not TRUE
OP_RETURN	0x6a	Halt and invalidate transaction

Table A-3 shows operators used to manipulate the stack.

Table A-3. Stack operations

Symbol	Value (hex)	Description
OP_TOALTSTACK	0x6b	Pop top item from stack and push to alternative stack
OP_FROMALTSTACK	0x6c	Pop top item from alternative stack and push to stack
OP_2DROP	0x6d	Pop top two stack items
OP_2DUP	0x6e	Duplicate top two stack items
OP_3DUP	0x6f	Duplicate top three stack items
OP_2OVER	0x70	Copy the third and fourth items in the stack to the top
OP_2ROT	0x71	Move the fifth and sixth items in the stack to the top
OP_2SWAP	0x72	Swap the two top pairs of items in the stack
OP_IFDUP	0x73	Duplicate the top item in the stack if it is not 0
OP_DEPTH	0x74	Count the items on the stack and push the resulting count
OP_DROP	0x75	Pop the top item in the stack
OP_DUP	0x76	Duplicate the top item in the stack
OP_NIP	0x77	Pop the second item in the stack
OP_OVER	0x78	Copy the second item in the stack and push it onto the top
OP_PICK	0x79	Pop value N from top, then copy the Nth item to the top of the stack
OP_ROLL	0x7a	Pop value N from top, then move the Nth item to the top of the stack
OP_ROT	0x7b	Rotate the top three items in the stack
OP_SWAP	0x7c	Swap the top three items in the stack
OP_TUCK	0x7d	Copy the top item and insert it between the top and second item.

Table A-4 shows string operators.

Table A-4. String splice operations

Symbol	Value (hex)	Description
OP_CAT	0x7e	Disabled (concatenates top two items)
OP_SUBSTR	0x7f	Disabled (returns substring)
OP_LEFT	0x80	Disabled (returns left substring)
OP_RIGHT	0x81	Disabled (returns right substring)
OP_SIZE	0x82	Calculate string length of top item and push the result

Table A-5 shows binary arithmetic and boolean logic operators.

Table A-5. Binary arithmetic and conditionals

Symbol	Value (hex)	Description
OP_INVERT	0x83	Disabled (Flip the bits of the top item)
OP_AND	0x84	Disabled (Boolean AND of two top items)
OP_OR	0x85	Disabled (Boolean OR of two top items)
OP_XOR	0x86	Disabled (Boolean XOR of two top items)
OP_EQUAL	0x87	Push TRUE (1) if top two items are exactly equal, push FALSE (0) otherwise
OP_EQUALVERIFY	0x88	Same as OP_EQUAL, but run OP_VERIFY after to halt if not TRUE
OP_RESERVED1	0x89	Halt - Invalid transaction unless found in an unexecuted OP_IF clause
OP_RESERVED2	0x8a	Halt - Invalid transaction unless found in an unexecuted OP_IF clause

Table A-6 shows numeric (arithmetic) operators.

Table A-6. Numeric operators

Symbol	Value (hex)	Description
OP_1ADD	0x8b	Add 1 to the top item
OP_1SUB	0x8c	Subtract 1 from the top item
OP_2MUL	0x8d	Disabled (multiply top item by 2)
OP_2DIV	0x8e	Disabled (divide top item by 2)
OP_NEGATE	0x8f	Flip the sign of top item
OP_ABS	0x90	Change the sign of the top item to positive
OP_NOT	0x91	If top item is 0 or 1 Boolean flip it, otherwise return 0
OP_0NOTEQUAL	0x92	If top item is 0 return 0, otherwise return 1
OP_ADD	0x93	Pop top two items, add them and push result
OP_SUB	0x94	Pop top two items, subtract first from second, push result
OP_MUL	0x95	Disabled (multiply top two items)
OP_DIV	0x96	Disabled (divide second item by first item)
OP_MOD	0x97	Disabled (remainder divide second item by first item)
OP_LSHIFT	0x98	Disabled (shift second item left by first item number of bits)
OP_RSHIFT	0x99	Disabled (shift second item right by first item number of bits)
OP_BOOLAND	0x9a	Boolean AND of top two items
OP_BOOLOR	0x9b	Boolean OR of top two items
OP_NUMEQUAL	0x9c	Return TRUE if top two items are equal numbers
OP_NUMEQUALVERIFY	0x9d	Same as NUMEQUAL, then OP_VERIFY to halt if not TRUE
OP_NUMNOTEQUAL	0x9e	Return TRUE if top two items are not equal numbers
OP_LESSTHAN	0x9f	Return TRUE if second item is less than top item
OP_GREATERTHAN	0xa0	Return TRUE if second item is greater than top item
OP_LESSTHANOREQUAL	0xa1	Return TRUE if second item is less than or equal to top item
OP_GREATERTHANOREQUAL	0xa2	Return TRUE if second item is great than or equal to top item
OP_MIN	0xa3	Return the smaller of the two top items
OP_MAX	0xa4	Return the larger of the two top items
OP_WITHIN	0xa5	Return TRUE if the third item is between the second item (or equal) and first item

Table A-7 shows cryptographic function operators.

Table A-7. Cryptographic and hashing operations

Symbol	Value (hex)	Description
OP_RIPEMD160	0xa6	Return RIPEMD160 hash of top item
OP_SHA1	0xa7	Return SHA1 hash of top item
OP_SHA256	0xa8	Return SHA256 hash of top item
OP_HASH160	0xa9	Return RIPEMD160(SHA256(x)) hash of top item
OP_HASH256	0xaa	Return SHA256(SHA256(x)) hash of top item
OP_CODESEPARATOR	0xab	Mark the beginning of signature-checked data
OP_CHECKSIG	0xac	Pop a public key and signature and validate the signature for the transaction’s hashed data, return TRUE if matching
OP_CHECKSIGVERIFY	0xad	Same as CHECKSIG, then OP_VERIFY to halt if not TRUE
OP_CHECKMULTISIG	0xae	Run CHECKSIG for each pair of signature and public key provided. All must match. Bug in implementation pops an extra value, prefix with OP_NOP as workaround
OP_CHECKMULTISIGVERIFY	0xaf	Same as CHECKMULTISIG, then OP_VERIFY to halt if not TRUE

Table A-8 shows nonoperator symbols

Table A-8. Non-operators

Symbol	Value (hex)	Description
OP_NOP1-OP_NOP10	0xb0-0xb9	Does nothing, ignored

Table A-9 shows operator codes reserved for use by the internal script parser.

Table A-9. Reserved OP codes for internal use by the parser

Symbol	Value (hex)	Description
OP_SMALLDATA	0xf9	Represents small data field
OP_SMALLINTEGER	0xfa	Represents small integer data field
OP_PUBKEYS	0xfb	Represents public key fields
OP_PUBKEYHASH	0xfd	Represents a public key hash field
OP_PUBKEY	0xfe	Represents a public key field
OP_INVALIDOPCODE	0xff	Represents any OP code not currently assigned