menghitung luas persegi dengan case

uses crt;
var
panjang:real;
luas:real;
lebar:real;
keliling:real;
diagonal:real;
pilihan:longint;
tampil:char;
begin
tampil := 'y';
while (tampil = 'y') or (tampil = 'Y') do
begin
textcolor(7);
textbackground(1);
textmode(80);
begin
clrscr;
gotoxy(19,1);writeln('---PROGRAM PERSEGI PANJANG BY NURUL HIDAYAH---');

gotoxy(19,2);writeln('--------------1 Menghitung Luas---------------');
gotoxy(19,3);writeln('-----------2 menghitung keliling--------------');
gotoxy(19,4);writeln('--------3 menghitung diagonal persegi---------');
gotoxy(19,5);write('pilihan:');
readln (pilihan);
case pilihan of
1: begin

gotoxy(19,6);write('masukan panjang = '); readln(panjang);
gotoxy(19,7);write('masukan lebar   = '); readln(lebar);
luas :=panjang*lebar;
gotoxy(19,8);writeln ('luas         = ',luas :12:0);readln;
gotoxy(19,9);write('Mau menghitung lagi atau tidak...? (y/n)');readln(tampil);
end;
2: begin

gotoxy(19,10);write('masukan panjang = '); readln(panjang);
gotoxy(19,11);write('masukan lebar   = '); readln(lebar);
keliling :=2*(panjang+lebar);
gotoxy(19,12);writeln ('keliling     = ',keliling :12:0);
readln;
gotoxy(19,13);writeln ('mau menghitung (y/n)');readln(tampil);
end;
3: begin

gotoxy(19,14);write ('masukan panjang ='); readln(panjang);
gotoxy(19,15);write ('masukan lebar   ='); readln(lebar);
diagonal :=sqrt(sqr(panjang)+sqr(lebar));
gotoxy(19,20);writeln ('diagonal      = ',diagonal :12:0);
readln;
writeln ('mau menghitung (y/n)');readln(tampil);
end;
end;
end;
end;
end.