Windows® via C/C++, Fifth Edition

When to Commit Physical Storage

Let’s pretend you’re implementing a spreadsheet application that supports 200 rows by 256 columns. For each cell, you need a CELLDATA structure that describes the contents of the cell. The easiest way for you to manipulate the two-dimensional matrix of cells would be to declare the following variable in your application:

CELLDATA CellData[200][256];

If the size of a CELLDATA structure were 128 bytes, the two-dimensional matrix would require 6,553,600 (200 × 256 × 128) bytes of physical storage. That’s a lot of physical storage to allocate from the paging file right up front for a spreadsheet, especially when you consider that most users put information into only a few spreadsheet cells, leaving the majority unused. ...