Program to illustrate exchange of values between two variables.
Also introduces assignment of string constants to string variables
and writeln statements with multiple arguments separated by commas.

	program exc;
	var
		x, y, t: string;
	begin
	x := 'tomato';
	y := 'blueberry');
	writeln('x = ', x, ' y = ', y);
	writeln('exchange');
	t := x;
	x := y;
	y := t;
	writeln('x = ', x, ' y = ', y);
	readln;
	end.

Sample output
>x = tomato y = blueberry
>x = blueberry y = tomato

Variation which reads in strings instead of assigning them.

	program exc;
	var
		x, y, t: string;
	begin
	readlnx(x);
	readln(y);
	writeln('x = ', x, ' y = ', y);
	writeln('exchange');
	t := x;
	x := y;
	y := t;
	writeln('x = ', x, ' y = ', y);
	readln;
	end.

Sample output:
<Diane
<Billy
>x = Diane y = Billy
>x = Billy y = Diane


Program introducing the use of variables of type integer and
illustrating the use of the "+" operator for integers

	program additions;
	var
		i, j, k: integer;
		a, b, c: string;
	begin
	writeln('Let us use "+" with integers:');
	writeln('i ?');
	readln(i);
	writeln('j ?');
	readln(j);
	k := i + j;
	writeln(i, ' + ', j, ' = ', k);
	writeln('Let us use "+" with strings:');
	writeln('a ?');
	readln(a);
	writeln('b ?');
	readln(b);
	c := a + b;
	writeln(a, ' + ', b, ' = ', c);
	readln;
	end.

Sample output:
>Let us use "+" with integers:
>i ?
<17
>j ?
<24
>17 + 24 = 41
>Let us use "+" with strings:
>a ?
<17
>b ?
<24
>17 + 24 = 1724