Programming Principles Spreadsheet-Based Decision Support Systems Chapter 24: Aslı Sencer MIS 463

2 Overview  24.1 Programming Practices  24.2 Clarity  24.3 Efficiency  24.4 Summary

3 Programming Practices  Issues related to coding in VBA for spreadsheet-based DSS development.  Clarity –Coding with a consistent style; –Using naming standards; –Having clear comments;  Increasing coding efficiency.

4 Consistent Style Use a consistent style for formatting, organizing, and commenting your code.  Spacing, indenting, line length should be consistent –Keep procedures and functions far enough so that scanning is easy –Indent to signify the beginning and end of a loop –Line length should be long enough to avoid scroll back and forth –Break lines at logical places  Be consistent at error checking –Check inputs in all input forms and worksheets Indenting not clear: If A is True Then ‘actions 1 ElseIf B is True Then ‘actions 2 End If Clearer indenting style: If A is True Then ‘actions 1 ElseIf B is True Then ‘actions 2 End If

5 Naming  Use naming standards for variables and procedures. –Abbreviate names so that they are not confused with other meanings. Ex:NumFac ? –When there is more than one word in a name capitalize the first letter. Ex: MinVal –Create descriptive names that are not lengthy Ex: “MinVal”, “SumProfit”, “MaxPrice” “FindMinCost”, “GetUserInfo” –Loop counters are usually i and j. May also use “iter”, or “run”  Naming standards also apply to control names and specific data types, Ex: The name of a textbox should start with “txt”, The name of a form should start with with “frm”, boolean varaible may start with “IsDone” or “DoAnimation” for constants use PI, INFINITY Procedure names: Use CalcReturn instead of Calc Function names: FindMinCost, GetUserInfo

6 Documentation  Make comments clear throughout the code.  Describe procedure functionality and loop and logical flow.

7 Efficiency  Always look for ways to improve your coding efficiency.  Avoid redundancies and unnecessary code. Static structure: For i = 1 to 10 ‘do actions Next i Dynamic structure: For i = 1 to NumProducts ‘do actions Next i

8 Efficiency (cont) Static structure: Dim CostArray(10) as Double Dynamic structure: Dim CostArray() As Double, CostSize As Integer ReDim CostArray(CostSize) Static structure: ‘paste in output table Range(“A1”).PasteSpecial Dynamic structure: Dim OutputTable As Range Set OutputTable = Range(“A1”) OutputTable.PasteSpecial

9 Summary  The most important programming principles are writing with a consistent style, using naming standards, including clear comments, and improving code efficiency.  It is important to have a clear, readable, and understandable code.  Documentation is an important part of any programming project. We accomplish documentation by placing comments throughout our code.  We should continuously be working to improve our code by reducing the complexity of the logic and the time required.