Procedures may also accept variables (data) to work with when they are called.

Declaring the variables within the procedure

• The variables accepted by the procedure are enclosed using parenthesis.
  
• The declaration of the accepted variables occurs between the procedure name and the terminating semi-colon.

Calling the procedure and Passing variables (or values) to it

• When the procedure is invoked, the procedure name is followed by a set of parenthesis.
  
• The variables to be passed are written inside the parenthesis.
  
• The variables are written in the same order as specified in the procedure.

Consider the following program example,

	program ADD_NUMBERS (input, output);

	procedure CALC_ANSWER ( first, second : integer );

	var   result : integer;

	begin

	      result := first + second;

	      writeln('Answer is ', result )

	end;
	var   number1, number2 : integer;

	begin

	      writeln('Please enter two numbers to add together');

	      readln( number1, number2 );

	      CALC_ANSWER( number1, number2)

	end.