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

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

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.

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.

Symbol | Value (hex) | Description |

| 0x7e | Disabled (concatenates top two items) |

| 0x7f | Disabled (returns substring) |

| 0x80 | Disabled (returns left substring) |

| 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.

Symbol | Value (hex) | Description |

| 0x83 | Disabled (Flip the bits of the top item) |

| 0x84 | Disabled (Boolean AND of two top items) |

| 0x85 | Disabled (Boolean OR of two top items) |

| 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.

Symbol | Value (hex) | Description |

OP_1ADD | 0x8b | Add 1 to the top item |

OP_1SUB | 0x8c | Subtract 1 from the top item |

| 0x8d | Disabled (multiply top item by 2) |

| 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.

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

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.

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 |

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