(SQL Plus|SqlCl) (Oracle Database Console)

About

SQLPlus is the first client of the Oracle Database.

SQL*Plus does not have a SQL or PL/SQL command parser. It scans the first few keywords of each new statement to determine the command type, SQL, PL/SQL or SQL*Plus.

Article

SQL Plus - Variable
SQL Plus - Command Reference
SQL Plus - Startup Script
SQL Plus - Formatting Reports
SQL Plus - Special Characters
SQL Plus - How to connect to a particular oracle database instance ?

User Interface

On windows, there is two versions of SQL*Plus :

a GUI one (sqlplusw.exe) Officialy deprecated in the next release of Oracle.
a DOS based character-mode one (sqlplus.exe)

Reference / Documentation

Documentation Reference
Database Administration with SQL*Plus