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Software Engineering and Program Construction

Debugging tools: breakpoints, stepping and watches

  • 3 things to know
  • AS Unit 1

Overview

Stepping into a subroutine call and stepping over it, why a debugger finds logic errors that the translator cannot and variable trace.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Key term

Explain how a conditional breakpoint helps when a loop runs thousands of times.

Key term

How would single stepping reveal a loop that repeats one time too many?

Key term

Why is using a debugger usually better than inserting statements that print values?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is a debugger?

    Model answer

    It is a tool that runs a program under control so its execution can be halted, taken one statement at a time and inspected while the values inside it are examined.

  2. 2

    What is a breakpoint?

    Model answer

    It is a marker placed on a line so that execution stops just before that line is carried out, letting the programmer inspect the state of the program at that exact point.

  3. 3

    Explain how a conditional breakpoint helps when a loop runs thousands of times.

    Model answer

    The breakpoint is set to fire only when a stated condition holds, such as a counter reaching a particular value, so the program runs at full speed until it reaches the case that is going wrong.

  4. 4

    What is a watch?

    Model answer

    It is a variable or expression the debugger displays continuously, so its value can be seen changing as each statement is carried out.

  5. 5

    Distinguish between stepping into a subroutine call and stepping over it.

    Model answer

    Stepping into enters the subroutine and executes it a statement at a time; stepping over runs the whole call at full speed and stops at the next statement of the calling routine.

  6. 6

    When would a programmer choose to step over a call rather than into it?

    Model answer

    When the subroutine is already known to work, so there is nothing to learn from watching it and the fault is being looked for elsewhere.

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