Unfortunately, you are mixing languages, as it were. Spool and Desc are SQL*PLUS commands, and not part of SQL or PL/SQL.

What you may want to do is

DBMS_OUTPUT.PUT_LINE ( "describ emp.c_ctron_rec.table_name; "_;

...instead.

Then, when you finish running this anonymous block in SQL*PLUS, you can get the output (however that is done in SQL*PLUS - hate the tool myself :)) and you will have a script that describes all your tables. You can then wrap that in the spool statements and you are good to go. Of course, you could also use one of a hundred utilities and applications out there to browse your tables as well.

Anyway, hope this helps,

- Chris