# Version-Related Opcodes Restored

Chronicle restored the version-related opcodes that enable scripts to behave differently based on transaction version:

| Opcode           | Input | Output  | Restored Function                            |
| ---------------- | ----- | ------- | -------------------------------------------- |
| **OP\_VER**      | -     | version | Pushes transaction version onto stack        |
| **OP\_VERIF**    | -     | -       | Conditional: executes if version ≥ threshold |
| **OP\_VERNOTIF** | -     | -       | Conditional: executes if version < threshold |

**Understanding Transaction Versioning**

Bitcoin transactions include a **version field** that indicates which ruleset the transaction follows. After Chronicle, transactions using a version > 1 will utilize the Chronicle ruleset. Transactions that have a version field of 1 will remain on the pre-Chronicle ruleset.

**Transaction version determines:**

* **Which opcodes are available:** Chronicle version enables all restored opcodes
* **Which validation rules apply:** Different versions may use different consensus rules
* **Backward compatibility:** Old transactions continue validating under old rules

**OP\_VER** retrieves this transaction version and pushes it onto the stack, enabling version-aware script logic.

#### OP\_VERIF: Version-Based Conditional Execution

**OP\_VERIF** performs a **greater-than-or-equal-to check** against the transaction version. It's followed by a version threshold value, and the subsequent script block executes only if the transaction version is greater than or equal to that threshold.

**Syntax:**

```
OP_VERIF
  <threshold_version>
  # This block executes if transaction version >= threshold
OP_ELSE
  # This block executes if transaction version < threshold
OP_ENDIF
```

#### Example: Version-dependent behavior

```
OP_VERIF
  OP_3  # Chronicle version threshold
  # Use Chronicle-specific features
  <data1> <data2> OP_CAT
  OP_SHA512
OP_ELSE
  # Fallback for older versions
  <data1> <data2> 
  # Use pre-Chronicle workaround
OP_ENDIF
```

This enables scripts that adapt to the transaction version, using advanced features when available while maintaining compatibility with older transaction versions.

#### OP\_VERNOTIF: Inverted Version Conditional

**OP\_VERNOTIF** works oppositely to OP\_VERIF—it executes the script block if the transaction version is **less than** the threshold:

```
OP_VERNOTIF
  OP_3  # Chronicle version threshold
  # This block executes if transaction version < 3
  # (pre-Chronicle behavior)
OP_ELSE
  # This block executes if transaction version >= 3
  # (Chronicle-enabled behavior)
OP_ENDIF
```


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