Blockchain Developer Certification Practice

What happens to the code execution if a boolean expression in require fails?

1. Execution continues as normal

2. Execution pauses for user confirmation

3. Code execution stops

4. Code is rerun from the beginning

The correct answer is: Code execution stops

When a boolean expression in a require statement fails, code execution stops immediately. The purpose of the require statement in programming, particularly in smart contracts within the blockchain context, is to enforce certain conditions that must be met for the code to proceed. If the required condition evaluates to false, the execution halts, reverting any changes made during that transaction. This mechanism ensures that the contract maintains its integrity and adheres to predefined rules. The failure of a require statement initiates a rollback, which means any operations that occurred prior to the failure are undone. This control flow is crucial for maintaining the expected behavior of a smart contract, as it allows developers to implement checks that validate conditions before allowing further execution, safeguarding against invalid states and potential exploits. While the other choices suggest different behaviors, they do not accurately reflect the nature of the require function's operation. Execution does not continue normally, nor does it pause for user confirmation, and there is no re-execution from the beginning. The require statement serves as a checkpoint in the code, reinforcing the validity of conditions required for successful execution.