CLAD Debugging & Troubleshooting Techniques 2 — Questions and Answers
Question 1: What does the Execution Highlighting (light bulb) feature do in LabVIEW?
- Compiles the VI for faster execution
- Animates data flow through wires so you can observe values at runtime (Correct answer)
- Highlights broken wires in red
- Enables automatic error handling on all nodes
Correct answer: Animates data flow through wires so you can observe values at runtime
Execution Highlighting animates the flow of data through the block diagram, displaying intermediate values on wires as the VI runs slowly.
Question 2: When using the Probe tool on a wire during debugging, what information is displayed?
- The wire's data type only
- The last value that passed through the wire during execution (Correct answer)
- The memory address of the wire buffer
- The number of times data has flowed through the wire
Correct answer: The last value that passed through the wire during execution
The Probe tool displays the last value that passed through a wire, allowing you to inspect intermediate data during or after execution.
Question 3: Which window in LabVIEW lists all errors and warnings in a VI and allows you to navigate directly to the problematic node?
- Error List (Ctrl+L) (Correct answer)
- Output Window
- Find and Replace Dialog
- Profile Performance and Memory
Correct answer: Error List (Ctrl+L)
The Error List (opened with Ctrl+L) lists all broken run arrows, errors, and warnings and lets you double-click to jump to the offending node.
Question 4: What is the purpose of a Retain Wire Values setting when combined with probes in LabVIEW?
- It prevents wires from being garbage collected during run
- It saves the last value on each wire so probes can display data even after execution stops (Correct answer)
- It converts dynamic data type wires to fixed types
- It locks wire routing so diagrams cannot be edited
Correct answer: It saves the last value on each wire so probes can display data even after execution stops
Retain Wire Values keeps the last value on each wire in memory, so probes can display those values after execution completes for post-mortem analysis.
Question 5: A subVI shows a broken run arrow but the parent VI compiled without errors. What is the most likely cause?
- The subVI connector pane has unwired required terminals (Correct answer)
- The parent VI is using a newer LabVIEW version
- The subVI front panel is hidden
- The subVI is set to reentrant execution
Correct answer: The subVI connector pane has unwired required terminals
If a subVI's required connector pane terminals are not wired in the calling VI, the subVI will break but may not immediately break the parent if the parent already compiled with a cached connector.
Question 6: Which LabVIEW debugging technique allows you to pause execution at a specific node and inspect data before the node executes?
- Single-step execution using Step Into (Correct answer)
- Setting a breakpoint on the wire after the node
- Using the Probe Watch Window
- Enabling Error Handling at the node
Correct answer: Single-step execution using Step Into
Single-step execution (Step Into) pauses before each node executes, letting you inspect inputs and outputs one node at a time.
Question 7: What does a white/grey node icon (dimmed appearance) on the block diagram indicate during Execution Highlighting?
- The node has not yet executed in the current run (Correct answer)
- The node is disabled and will be skipped
- The node contains a runtime error
- The node is running in parallel on a separate thread
Correct answer: The node has not yet executed in the current run
During Execution Highlighting, dimmed nodes have not yet executed, while bright nodes have already run or are currently running.
CLAD Debugging & Troubleshooting Techniques 2
What does the Execution Highlighting (light bulb) feature do in LabVIEW?