Excel Add-in Development in C/C++: Applications in ... - F9

10 Excel Add-in Development in C/C++Table 2.2 (continued)A1 styleR1C1 styleLeft-most column in sheet A C1Right-most column in sheet IV C256Relative reference style as shown by formula =A2entered into cell B1.=A2 =R[1]C[-1]Absolute reference style as shown by formula =$A$2entered into cell B1.Mixed reference style as shown by formula =A$2entered into cell B1.=$A$2=$A2=R2C1=R2C[-1]Relative reference in same row or column as shownby formula =A2 entered into cells B2 and A1.=A2 =RC[1] (in cell A1)=R[-1]C (in cell B2)Note: The index in square brackets in relative references in R1C1 style can be any numberfrom −65,535 to +65,535 inclusive.2.3 CELL CONTENTSInternally, a cell within Excel has a great deal of data associated with it. This includes thedisplay format, attached comments (notes), protection status, etc. The two most importantproperties for someone wishing to write functions are:1. The cell’s formula – a text string that Excel parses to an internal compiled form, andwhich is then used to re-evaluate the cell in a recalculation.2. The cell’s value – if the cell contains a formula, the result of its evaluation, otherwisethe data that was entered directly by the user or an Excel command or macro.2.4 WORKSHEET DATA TYPES AND LIMITSFrom a spreadsheet user’s perspective, the type of value of any non-empty cell (or groupof cells in the case of an array) will always be one of the following:• a number (floating point);• a Boolean value (TRUE or FALSE);• a character string;• an Excel-specific error code;• an array comprised, in general, of a mixture of the above types.Excel will always evaluate a cell formula to one of these data types. Sometimes thefunction in the cell will return something other than one of these, such as a range reference,but Excel will then evaluate this to one of these types.The formatting applied to a cell can, of course, make the appearance of a number itcontains very different. A number may appear as a date, a time, a percentage, a currencyamount, in scientific notation or as a formatted fraction. Note that Excel doesn’t distinguishbetween integer and floating-point numbers on a worksheet. A function that takes integer