This is a screen-capture (12 July 2017) of the web-page

https://www.cog-genomics.org/plink/1.9/formats

which documents the PLINK file formats used in some of the UK Biobank genetic data.

Please refer to, and reference in any publications, the original web-page rather than this frozen document.

This resource can be downloaded or viewed using the link: plink19formats.pdf

If you have wget available (typically on linux systems), then you can also obtain a copy using the command

 wget  -nd  biobank.ndph.ox.ac.uk/ukb/ukb/docs/plink19formats.pdf