In SQL * Plus, how does one use '&' to implement custom parameter variables?

In SQL * Plus, how does one use '&' to implement custom parameter variables?

software environment: 1. Windows NT4.0 + Oracle 8.0.4 2. Oracle installation path: C: \ orant Implementation Method: SQL> select * From & table_name; table_name input value: dba_users original (value) 1: Select * From & table_name new (value) 1: select * from your username user_id password default_tablespace created profile -------- too many characters ----------- ------- sys 0 hour system 30-oct-97 default system 5 hour user_data temporary_data 30-oct-97 default Scott 10 hour user_data limit 30-oct-97 default Query to 3 Records. SQL>