What type of language is Bitcoin Script?

Bitcoin Script is a stack-based scripting language that uses reverse Polish notation.

Why is Bitcoin Script deliberately not Turing complete?

Bitcoin Script has no loops to prevent infinite execution, ensuring predictable fees and preventing DoS attacks.

What does OP_CHECKSIG do?

OP_CHECKSIG verifies that the provided signature is valid for the given public key and transaction.

In a P2PKH script, what does OP_DUP do?

OP_DUP duplicates the top item on the stack, which is needed to preserve the public key for later verification.

What is the maximum size allowed for OP_RETURN data?

OP_RETURN allows embedding up to 80 bytes of arbitrary data in the blockchain.

Bitcoin Script Programming

16 min readarticleIncludes quiz · 5 questions

Learn Bitcoin's scripting language and how to create custom transaction conditions.

Script Basics:

•Stack-based: Operations manipulate a stack
•Forth-like: Reverse Polish notation
•Deliberately limited: No loops (Turing incomplete)
•Predicate: Returns true/false

Common Opcodes:

•OP_DUP: Duplicate top stack item
•OP_HASH160: Hash with RIPEMD-160(SHA-256())
•OP_EQUALVERIFY: Check equality and fail if false
•OP_CHECKSIG: Verify signature

Example P2PKH Script:

`scriptPubKey:` `OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG`

`scriptSig:` `<signature> <publicKey>`

Execution flow: 1. Signature and public key pushed to stack 2. OP_DUP duplicates public key 3. OP_HASH160 hashes the public key 4. Compare with stored hash 5. Verify signature

Advanced Script Features:

•OP_IF/OP_ELSE: Conditional execution
•OP_CHECKMULTISIG: M-of-N signatures
•OP_CHECKLOCKTIMEVERIFY: Time locks
•OP_CHECKSEQUENCEVERIFY: Relative time
•OP_RETURN: Provably unspendable outputs

These enable complex smart contracts like escrow, inheritance, and atomic swaps.

Test Your Knowledge

This lesson includes a 5-question quiz (passing score: 75%).

Quiz functionality available in the mobile app.