Interpreting a SAS code on freq procedure

Question

I have come across following SAS code

proc freq data mydata;
tables _char_;
run;

I fail to understand what char implies here. Is it some reserve word for SAS? What does it do? What are similar things exist in SAS?

Answer 1

It is SAS variable list short for all character variables in data set referenced in DATA= proc statement option.

_CHAR_ aka _CHARACTER_ 

SAS Variable Lists