# Key Takeaways Constant value opcodes and pushdata opcodes form the foundation of Bitcoin Script, enabling all data to reach the stack where it can be processed. **Constant opcodes (OP\_0 through OP\_16, OP\_1NEGATE)** provide efficient single-byte shortcuts for commonly used small integers, particularly valuable in multisignature scripts and counters. **Pushdata opcodes** handle arbitrary data efficiently across all size ranges: inline pushdata (0x01-0x4B) for typical signatures and keys up to 75 bytes, OP\_PUSHDATA1 for medium data up to 255 bytes, OP\_PUSHDATA2 for large data up to 65KB, and OP\_PUSHDATA4 for very large data up to 4GB. The **minimal encoding rule** ensures every script uses the smallest appropriate opcode, maintaining efficiency and standardization. The **pushdata-only rule for input scripts** serves as a crucial security boundary: inputs provide data only (via pushdata and constant opcodes), while output scripts define operational logic. This separation prevents script injection attacks and ensures predictable validation behavior. Understanding these fundamental building blocks prepares you for more complex scripting patterns, as virtually every Bitcoin Script begins with pushing data onto the stack using these opcodes. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://hub.bsvblockchain.org/higher-learning/bsv-academy/bsv-opcodes/constant-value-and-pushdata-opcodes/key-takeaways.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.