Excel is a spreadsheet written by '''The Evil Empire''' [http://www.microsoft.com/].  It is a part of their MS Office suite of software--a
hazardously flawed
[http://www.burns-stat.com/pages/Tutor/spreadsheet_addiction.html#excel] part, incidentally.


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Ways to get to .xls data:
[DDE];
[COM], especially [tcom];
[CSV];
[ODBC] (there are rumors of faults in the drivers, though);
[Victor Wagner]'s xls2csv [http://www.ice.ru/~vitus/catdoc];
xhHtml [http://chicago.sourceforge.net/xlhtml] is a command-line utility
that can create XML output;
Spreadsheet::ParseExcel
[]
and related [Perl]-coded modules
available through [CPAN];
Christoph Bauer's tclexcel
[http://www.rhrk.uni-kl.de/~bauerc/tclexcel.html]; http://www.greytrout.com;
[SYLK];
the [Python]-based 
http://sourceforge.net/projects/pyxlwriter/ ;
...

The name of the native Excel file format apparently is BIFF.
At some point, it'll be valuable to document the location of [Microsoft]
references on BIFF, as well as whether the Perl and Python modules write
formatted plaintext, or BIFF.

There is a freely-available Excel viewer
from Microsoft (MS Windows only)
[http://office.microsoft.com/downloads/2000/xlviewer.aspx];
For Linux/Unix, Gnumeric [http://www.gnome.org/projects/gnumeric/]
and StarOffice [http://www.staroffice.com/] can import Excel files;

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I have written a tcl wrapper [Using Perl to get Excel] to make the writing of excel files using perl's Spreadsheet:WriteExcel very managable - [JBR].

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More information is available through http://www.wotsit.org/ [[find more precise URL]]. 
http://www.wotsit.org/download.asp?f=xls

Links directly to the fileformat are not allowed anymore on wotsit. So you have to go
to "Spreadsheet/Database" and look for "XLS".


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[["If you tab delimit the data and name it myfile.xls, current versions of
excel will 'do the right thing'."]]  [CL] has recently had
success with "pipe-delimiting"; that is, writing tabular
data as simply as possible, with '|' separating fields.
Office workers seem to accept this as "spreadsheet format".  Later, in fall 2004,
CL's finding abundant headaches with [CSV] and tab- and pipe-delimitation,
but is happy with results from [HTML] formatting into a <TABLE>.

[Benny Riefenstahl]: I have also have had success in opening simple HTML
tables with Excel directly.  This has the advantage of having a well-defined
character encoding and makes it possible to use long multi-line text in cells.

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The class library "Jakarta POI - HSSF - Java APIs with XML manipulate MS-Excel" (http://jakarta.apache.org/poi/hssf/) can be used in combination with [TclJava].
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Example fragment of COM-based access (read) of Excel spreadsheet:

    set cellVal [[$cells Item $msgNum $column] -get Value]
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If you view a CSV file in Excel, columns are labeled A..Z, AA..AZ, BA..
To convert these column labels to numeric indexes (0..), so as to access the data with [lindex], here's a little helper:
 proc excel'col2int col {
     set abc {- A B C D E F G H I J K L M N O P Q R S T U V W X Y Z}
     set int 0
     foreach char [split $col ""] {
          set int [expr {$int*26 + [lsearch $abc $char]}]
     }
     incr int -1 ;# one-letter columns start from A
 } ;# RS

See [Mapping words to integers] for a more general take.
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It amuses the archaeologically inclined that, as [KBK] observes, "The kernel
of the Excel solver is the singular-value decomposition from Wilkinson
[[presumably '''Handbook for Automatic Computation Volume II - Linear Algebra''']].
That's
essentially 1971-vintage [Algol], rewritten first in [Fortran] and then in [C]."


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The VBA Object Browser (OB) provides access to "the procedures, objects, ... available for
use in the active workbook ..."

To reach the OB, select "Tools/Macro/Visual Basic Editor".  Once VB comes up, you should see a funny illustrated 
square icon near the right side of VB's standard toolbar; that's the OB, as its [tooltip] promises.

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"[How to launch a Tcl program from Excel]"

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[Category Application]