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ME 142 Engineering Computation I

ME 142 Engineering Computation I. Debugging Techniques. Key Concepts. Types of Program Errors Debugging Tools & Techniques Testing. Types of Programming Errors. Syntax Errors Run-Time Errors Logic Errors. Syntax Errors.

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ME 142 Engineering Computation I

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  1. ME 142Engineering Computation I Debugging Techniques

  2. Key Concepts • Types of Program Errors • Debugging Tools & Techniques • Testing

  3. Types of Programming Errors • Syntax Errors • Run-Time Errors • Logic Errors

  4. Syntax Errors • Syntax errors occur when the rules of the programming language are violated. • Examples: • Misspelling a keyword or function name • Misplacement or omission of a parenthesis or quote mark • Omission of necessary keywords in a command.

  5. Run-Time Errors • Runtime errors are those errors that occur when a program free of syntax errors, runs and generates an error. • Examples: • Attempting an invalid operation such as division by zero • Providing the wrong data type to a function.

  6. Logic Errors • Logic errors are due to incorrect program logic. • The program may run without errors • The results it returns are inaccurate. • Often the most difficult to locate

  7. Debugging Tools & Techniques • MsgBox Function • Debug.Print Statement • Debug Mode

  8. MsgBox Statement • Place MsgBox statement in your code as desired • Causes the value of the variables to be immediately displayed in a dialog box and pauses execution of program • Example: MsgBox (“A = “ & A)

  9. Debug.Print Statement • Place Debug.Print statement in your code as you would MsgBox function • Causes the value of the variables to be printed in the Immediate window • Example: Debug.Print A,B,C

  10. Debug.Print Statement

  11. Debug Mode • Allows you step through your program and examine the value of variables at specific points • May step through line-by-line or set specific breakpoints

  12. Debug Mode • When a run-time error occurs may enter Debug Mode by selecting button on dialog box that appears:

  13. Debug Mode • Once in Debug Mode may mouse-over a variable to find its current value:

  14. Debug Mode • May also hit the F8 key to single step through the program • Each time the F8 key is hit, one line of code is executed:

  15. Debug Mode • May also set a breakpoint by clicking in the gray column on the left side of the line of code you want to program to pause on • Click on run (from menu above) to cause the program to resume

  16. Debug Mode • Another powerful feature to use in conjunction with the previous techniques is the Locals Window • It displays the current value of all local variables in your program

  17. Testing • Deadly Misconception of Beginning Programmers: • If a program runs without errors, the results must be correct • Very important that before you use your program to make engineering decisions (or turn it in to get a grade in class) that you perform a series of test to make certain that the output is correct.

  18. Testing Suggestions • Compare your results to that of a simple, known problem by using a calculator or Excel • Test a typical range of inputs • Test unusual but valid data • Test extreme values

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