The problem with using the Procedure in Pascal - pascal

Question

uses GraphABC;
var
x, y, a: integer;
procedure treug(x, y, a, b: integer);
begin
x := 0;
y := 20;
line(x, y, x+a, y);
line(x, y, x, y+b);
line(x+a, y, x, y+b);
end;
begin
writeln('Enter the length of the catheter');
read(a);
while y < 480 do
begin
y := y+1;
treug(x, y, a, a);
end;
end.
Outputs only one triangle, and not the desired number up to the vertical border.
I expected one vertical row of right triangles (x and y are the coordinates of the right angle) to the lower border of the graphic window.

Answer 1

uses GraphABC;
var
x, y, a: integer;
procedure treug(x, y, a, b: integer);
begin
line(x, y, x+a, y);
line(x, y, x, y+b);
line(x+a, y, x, y+b);
end;
begin
writeln('Enter the length of the catheter');
read(a);
x := 0; // <-- initialize your x and y here
y := 20;
while y < 480 do
begin
y := y+1; // (see note below)
treug(x, y, a, a);
end;
end.
Remember, you have two sets x and y variables:
The global ones declared in the main program (and now properly initialized in the main program)
The ones local to the treug() procedure.
Things may have the same name and not be the same thing. If it helps, you can think of the global x as GraphABC.x and the local x as GraphABC.treug.x.
BTW, you probably want to increment y by something more than 1 each time through the loop, otherwise it’ll look just like a single triangle has been smeared down the display. (You might want to increment by b.)