There is only one file type that uses the .NCSS extension:
NCSS Dataset File
File created by NCSS, a statistical analysis system; contains data in worksheets made up of columns and rows that can be customized by the user; includes any applied filters, automatic transfer calculations, conditional transformations, and column notes; holds a maximum of 2 billion rows and 2 billion columns.
NOTE: The NCSS file format was introduced in NCSS 8 and replaced the "s0" and "s0z" file extensions.
Updated: August 30, 2014