Задача на Ломанную Линию

Program Litvinov_Kursovaja;
Uses crt,graph;
Const w:array[1..3] of string[99]=('O programme','Narisovat'' grafik','Vuhod');
len=20;
g=len div 5;
Var bac,a,b,c:word;
PT:char;
booster:boolean;
gm,gd:integer;
ct:string;
i,angle,old_angle:word;
d,r,n:integer;

function K(i:word):byte;
begin
if Odd(i) then K:=i mod 4 else K:=K(i div 2)
end;

{-----------------------------------------------------------------------}
{ Risyet na ekrane menu }
{-----------------------------------------------------------------------}

Procedure Menu(c:word);
Begin
ClrScr;
for bac:=1 to 3 do
begin
if bac=c then
TextColor (20)
else
TextColor (3);
GoToXY(28,10+bac);
writeln (w[bac]);
end;
end;

{-----------------------------------------------------------------------}
{ Pynkt 'O programme' }
{-----------------------------------------------------------------------}

Procedure about_programm;
Begin
ClrScr;
TextColor (2);
GoToXY (35,3);
writeln ('O PROGRAMME');
GoToXY(25,11);
TextColor (3);
writeln ('Vipolnil:');
GoToXY(40,11);
TextColor (5);
writeln ('Litvinov M.S.');
GoToXY (25,12);
TextColor (3);
writeln ('Gruppa:');
GoToXY (40,12);
TextColor (4);
writeln ('C-17051');
GoToXY (25,13);
TextColor (3);
writeln ('Prepodavatel'':');
GoToXY (40,13);
TextColor (6);
writeln ('Slyzhenikina N.V.');
GoToXY (10,20);
TextColor (20);
writeln ('Zadanie:');
GoToXY (20,20);
TextColor (10);
writeln ('Programma dolzha narisovat'' lomannyu liniu');
GoToXY (20,21);
TextColor (10);
writeln ('pod ypravleniem kyrsora');
readln;
End;


{-------------------------------------------------------------------------}
{ Peredvizhenie linii po strelkam }
{-------------------------------------------------------------------------}

Procedure Strelki;
Begin
case angle of
0: begin
if old_angle=90 then LINEREL(-g,-g) else LINEREL(g,-g);
LINEREL(0,-(len-2*g))
end;

180: begin
if old_angle=90 then LINEREL(-g,g) else LINEREL(g,g);
LINEREL(0,len-2*g);
end;

90: begin
if old_angle=0 then LINEREL(-g,-g) else LINEREL(-g,g);
LINEREL (-(len-2*g),0)
end;

270: begin
if old_angle=0 then LINEREL(g,-g) else LINEREL(g,g);
LINEREL (len-2*g,0)
end;
end;
End;

{--------------------------------------------------------------------------}
{ Narisovat' Grafik }
{--------------------------------------------------------------------------}

Procedure grafik;
Begin
gd:=detect;
InitGraph(gd,gm,ct);
ClearDevice;
MoveTo(190+a,276);
angle:=270;
LINEREL(len-g,0);
old_angle:=270;
n:=418;
for i:=1 to n-1 do
begin
angle:=(angle+K(i)*90) mod 360;
DELAY(2000);
Strelki(angle,old_angle);
end;
repeat until keypressed;
CloseGraph;
End;



{--------------------------------------------------------------------------}
{ Kod programmu }
{--------------------------------------------------------------------------}

Begin
ClrScr;
booster := False;
b:=1;
c:=1;
menu (c);
repeat
PT:=readkey;
{a:=ord(PT);}

if PT=chr(0) then
begin PT:=readkey;
a:=ord (PT);
Case PT of
chr(72):
if c=1 then
c:=3
else
c:=c-1;
chr(80):
if c=3 then
c:=1
else c:=c+1;
else begin
GoToXY (10,25);
TextColor (12);
writeln ('Ne ta klavisha');
readln;
end;
end;
end
else
begin
case PT of
chr(27):
b:=0;
chr(13):
case c of
1: about_programm;
2: grafik;
else b:=0;
end;
else
begin
GoToXY (25,8);
TextColor (12);
writeln ('Nazhata ne ta klavisha !!!');
readln;
end;
end;
end;
menu(c);
until b=0;
end.