Hi Sergio,
The SAS help has all the resources you need, but sometimes I find it easier to navigate on a more text-link-based page, as opposed to the Java-dependent SAS OnlineDoc.
Check out this resource:
http://www.csc.fi/cschelp/sovellukset/stat/sas/sasdoc/sashtml/main.htm and click on "SAS Procedures Guide" under Base SAS. If all you're looking for is a simple frequency, I'd still suggest Proc Freq, as you had previously attempted.
proc freq data = table_y;
tables x;
run;
"Tables" in proc freq works kind of like "Var" in proc print, if that makes it easier to grasp. If you had to do a two-way frequency between x and z, the line would read "tables x*z", for instance.
You can click through the various links within to see the options of proc freq/tables/output/etc so you have a better idea of how to tweak your code. The examples (once again, taken directly from the SAS OnlineDoc) are very good and helped me figure my way through many programming projects when I was a student.
Elayne