PROCEDURE:-IT IS A COMPILED BLOCK OF CODE WHICH IS STORED AS AN OBJECT WITHIN THE DATABASE. IT MAY OR MAY NOT RETURN ANY VALUE OR MIGHT RETURN MORE THAN ONE VALUE.
syntax
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CREATE [OR REPLACE] PROCEDURE PROCEDURENAME([PARAMETER PARAMETER MODE DATATYPE [,PARAMETER...,....]])
{IS/AS}
[LOCAL DECLARATION];
BEGIN
EXECUTABLE STATMENT;
[EXCEPTION
EXCEPTION HANDLER]
END [PROCEDURENAME];
SAMPLE EXAMPLE TO SHOW PARAMETER LESS PROCEDURE
==================================================
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CREATE OR REPLACE PROCEDURE list_tables AS
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BEGIN
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dbms_output.put_line('These are the tables you own:');
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FOR item IN (SELECT table_name FROM user_tables)
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LOOP
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dbms_output.put_line(item.table_name);
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END LOOP;
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END;
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Parameters
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1.formal---declared In The Defination Of The Procedure.they Receive The Value.
2.actual---passed Within Parenthesis,to Execute The Procedure.
Parameter Mode--it Specifies What Can Be Done With The Parameters.
In/out/in Out
------------------------
In--(default)-it Lets To Pass A Value To The Subprogram Being Called.the Value Can't Be Changed Inside The Subprogram.it Is Like A Constant.it Can't Be Assigned Any Value.
Out--it Lets The Subprogram Pass A Value To The Caller.inside The Subprogram The Out Parameter Is An Un-initialised Variable.
Subprogram Has To Place A Value In The Out Parameter. What Ever Changes Are Made To The Out Parameter Are Made Available To The Actual Parameter.the Actual Parameter Corresponding To The Out Parameter Must Be A Variable.
In Out--it Is Same As In And Out Both Together.it Can Get A Value From The Calling Procedure And Can Return A Value To The Calling Procedure.the Value Of This Type Of Paramater Can Be Used In Subprogram And The Actual Parameter Must Be An Initialised Variable.
Also check
PL/SQL-PROCEDURES - 2 
