Модуль для операций с векторами

unit vect;
interface
type Vector=record
            x,y:real;
            end;
procedure Summa(a,b:Vector;var c:Vector);
procedure Razn(a,b:Vector;var c:Vector);
function Scal(a,b:Vector):real;
procedure UmnCh(var a:Vector;k:real);
Function Dlina(a:Vector):real;
implementation
procedure Summa;
begin
c.x:=a.x+b.x;
c.y:=a.y+b.y;
end;
procedure Razn;
begin
c.x:=a.x-b.x;
c.y:=a.y-b.y;
end;
function Scal;
begin
Scal:=a.x*b.x+a.y*b.y;
end;
procedure UmnCh;
begin
a.x:=a.x*k;
a.y:=a.y*k;
end;
Function Dlina;
begin
Dlina:=sqrt(sqr(a.x)+sqr(a.y));
end;
end.

unit vect;
interface
type Vector=record
            x,y:real;
            end;
procedure Summa(a,b:Vector;var c:Vector);
procedure Razn(a,b:Vector;var c:Vector);
function Scal(a,b:Vector):real;
procedure UmnCh(var a:Vector;k:real);
Function Dlina(a:Vector):real;
implementation
procedure Summa(a,b:Vector;var c:Vector);
begin
c.x:=a.x+b.x;
c.y:=a.y+b.y;
end;
procedure Razn(a,b:Vector;var c:Vector);
begin
c.x:=a.x-b.x;
c.y:=a.y-b.y;
end;
function Scal(a,b:Vector):real;
begin
Scal:=a.x*b.x+a.y*b.y;
end;
procedure UmnCh(var a:Vector;k:real);
begin
a.x:=a.x*k;
a.y:=a.y*k;
end;
Function Dlina(a:Vector):real;
begin
Dlina:=sqrt(sqr(a.x)+sqr(a.y));
end;
end.

uses vect;
const max=20;
var a:array[1..max] of Vector;
    n,i,j:byte;
    x:Vector;
begin
randomize;
repeat
write('Введите количество векторов от 2 до ',max,' n=');
readln(n);
until n in [2..max];
writeln('Исходные вектора');
for i:=1 to n do
with a[i] do
 begin
  x:=-5+10*random;
  y:=-5+10*random;
  write(i:2,'(x=',x:5:2,' y=',y:5:2,' dlina=',Dlina(a[i]):5:2,') ');
  if i mod 2=0 then writeln;
 end;
writeln;
//сортировка
for i:=1 to n-1 do
for j:=i+1 to n do
if Dlina(a[i])< Dlina(a[j]) then
 begin
  x:=a[i];
  a[i]:=a[j];
  a[j]:=x;
 end; 
writeln('Вектора в порядке убывания длин');
for i:=1 to n do
with a[i] do
 begin
  write(i:2,'(x=',x:5:2,' y=',y:5:2,' dlina=',Dlina(a[i]):5:2,') ');
  if i mod 2=0 then writeln;
 end;
end.