27. September 2013
Using Shared Strings to Reduce Memory Usage
As of Excel 2007, files are saved in the Open XML format. This format is comprised of a grouping of XML files and assets, which are then zipped up and given the .xlsx extension. It’s a lot more readable from other programs than an old fashioned .xls file.
One means that was used to reduce the file size was setting up a shared strings table. Strings stored in a spreadsheet are given a numeric index and this numeric index is then stored in the xml file. In general, if a string is reused frequently the overhead of the shared string map will be payed off by the saving of only storing string indices.