Bitcoin Script

Execute locking conditions one opcode and stack item at a time.

Follow these 10 lessons in order, or choose the topic you need. Each lesson combines an explanation, a worked example and practice inside the Guild.

1. Stack-machine execution

   Script is a deliberately constrained stack language whose success depends on final truth and consensus limits.

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2. Pushes, arithmetic, and control flow

   Data pushes, numeric encodings, conditionals, and verification opcodes compose spending policies.

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3. Signature checks and sighashes

   CHECKSIG validates a signature over a transaction digest selected by a sighash mode.

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4. P2PKH and P2SH

   Legacy templates separate address-friendly commitments from revealed spending scripts.

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5. Witness programs

   SegWit moves authorization data into witness structures and versions the program semantics.

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6. Multisig and policy composition

   Multiple keys, timelocks, and hashlocks can form recovery, escrow, and channel policies.

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7. Script limits and malleability

   Disabled opcodes, resource limits, encoding rules, and malleability protections constrain safe composition.

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8. Script debugging

   Experts trace every stack transition, identify the failing predicate, and distinguish malformed witnesses from false conditions.

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9. P2PK, P2PKH, P2MS, P2SH, and OP_RETURN

   Compare the exact assembly, serialized bytes, spend data, standard uses, and failure boundary for Bitcoin's classic Script templates.

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10. Native and nested SegWit scripts

    Construct P2WPKH, P2WSH, P2SH-P2WPKH, and P2SH-P2WSH outputs and follow each redeem, witness, hash, and signature check.

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