PROCEDURES WHICH ACCEPT ARGUMENTS
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.

	program  TestValue (output);
	var  x, y : integer;

	procedure  NoEffect ( x, y : integer );
	begin
	    x := y;  y := 0;
	    writeln( x, y )
	end;

	begin
	    x := 1;  y := 2;
	    writeln( x, y );
	    NoEffect( x, y );
	    writeln( x, y )
	end.