Further reading
SAS white paper Errors, Warnings, and Notes (Oh My) A Practical Guide to Debugging SAS Programs by Lora D. Delwiche and Susan J. Slaughter – available here: https://www.lexjansen.com/wuss/2016/168_Final_Paper_PDF.pdf
SAS white paper How SAS Thinks or Why the Data Step Does What it Does by Neil Howard, available here: https://support.sas.com/resources/papers/proceedings/proceedings/sugi28/189-28.pdf
SAS blog post Converting Variable Types – Use PUT() or INPUT()? by Sunil Gupta, available here: https://blogs.sas.com/content/sgf/2015/05/01/converting-variable-types-do-i-use-put-or-input/
SAS white paper Basic Debugging Techniques by Beatriz Garcia and Alberto Hernandez – available here: https://www.pharmasug.org/proceedings/2012/PO/PharmaSUG-2012-PO17.pdf
SAS blog post Six Ways to use the _NULL_ Data Set in SAS by Rick Wicklin – available here: https://blogs.sas.com/content/iml/2018/06/11/6-ways-_null_-data-set-sas.html...