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Computers in Civil Engineering CEE3100 Spring 2002 Lecture #3

Computers in Civil Engineering CEE3100 Spring 2002 Lecture #3. General Programming Concepts. Programming Concepts. General discussion Class-specific aspects. Programming Steps . Clearly identify and understand the problem Clearly identify the desired input and output

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Computers in Civil Engineering CEE3100 Spring 2002 Lecture #3

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  1. Computers in Civil EngineeringCEE3100 Spring 2002Lecture #3 General Programming Concepts

  2. Programming Concepts • General discussion • Class-specific aspects

  3. Programming Steps • Clearly identify and understand the problem • Clearly identify the desired input and output • Use ‘pseudo-code’ to design your solution strategy and algorithm • Write source code • debug, debug, and debug… the source code • Test code on cases with known results; revise source, compile, debug, .., test, … • Document code

  4. Algorithm • Definition • A Sequence of Logical Steps Required to Perform a Task • Characteristics • Finite number of steps • Considers all possibilities • Anticipates errors in input data

  5. Program Composition • Program • A sequence of instructions for computer • High-level Languages • FORTRAN.Original “language of engineers”; still popular for heavy-duty number-crunching; not the best for more general work • Pascal: a well-structured language; starting to be rare • C, C++, Java, Visual Basic: graphics, PC applications • Other • MATLAB, MATHEMATICA, MATHCAD

  6. Debugging & Testing • Types of errors (bugs): • Syntax (spelling) detected by compiler • Semantic (logic) Difficult to detect!

  7. Example – Logic Error ! Calculate arithmetic mean of a vector Dim n As Integer Dim m As Integer Dim sum As Single,average As Single Dim A(n) As Single ! (procedures to load A, scalar n) sum = 0.0 For i = 1 To n Sum = Sum + a(i) Next i average=sum/m ! Will the compiler catch this error?

  8. Some advice to avoid much grief: NEVER divide without first testing that the denominator is non-zero. If m = 0 then MsgBox “Oops: denominator m=0” else average=sum/n Endif ! The denominator may be a big nasty Expression: TEST IT FIRST!

  9. Documentation of Your Work • Internal (use of comments): worth its weight in gold! • External • README files • Messages printed by program • File naming conventions can be self-documenting You are the main user! Can you understand your work if you pick it up after five years????

  10. Storage and Maintenance • Logical Directory Organization. E.g.: ehabib/compce/module01/lab /hw • Make Backups: Keep multiple copies • Revisions • Try to avoid having multiple versions of a code – it only leads to grief

  11. Error-Mitigation Approach to Programming • Algorithm development & analysis • Modular design of code • Individual testing of code elements • Analysis of the solution • Explain your code to someone else

  12. To Be Continued …(Please read Chapter 2 of Chapra & Canale)

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