Нельзя преобразовать тип integer к char

Program KurRab;
Uses crt, GraphABC;
const 
n=5;
m=5;
Type
strmenu=record 
x: integer; 
s: string[14]; 
end;
Const
kol=4;
mas:array[1..kol] of strmenu=
((x:6; s:'Ввод данных'),
(x:20; s:'Сортировка'),
(x:50; s:'Вывод данных'),
(x:63; s:'Выход'));
Var
a:array[1..n,1..m] of integer;
b:array[1..n] of integer;
mass:array[1..5]of integer;
j:byte;
min,i,f,no:integer;
ch: char;
 
procedure InputDan;
begin 
var i,j: integer;
randomize;
for i:=1 to n do
begin
for j:=1 to m do
begin
a[i,j]:=random(10)-5;
write(a[i,j]:5);
end;
end;
end;
 
procedure SortDan;
begin
var i,j: integer; 
for i:=1 to n-1 do begin
for j:=i+1 to n do begin
if mass[i]>mass[j] then begin
f:=mass[i]; mass[i]:=mass[j]; mass[j]:=f
end;end;end;
end;
 
procedure OutputDan;
begin 
var no,i:integer;
for i:=1 to no do write(mass[i],5)
end;
Begin
no:=1;
repeat 
textColor(Red);
TextBackground(LightGray);
clrscr;
for i:=1 to kol do
begin
gotoxy(mas[i].x,3);
write(mas[i].s);
end;
textColor(Red);
TextBackground(LightGray);
gotoxy(mas[n].x,3);
write (mas[n].s); 
ch:=readkey; 
case ch of 
13: case no of 
1: InputDan; 
2: SortDan; 
3: Graphfun; 
4: OutputDan; 
end;
#0:begin
ch:=readkey;44:
case ch of 
#77:
if no<kol then
no:=no+1
else
no:=1;
#75:
if no>1 then
no:=no-1
else
no:=kol;
end;
end;
end;
until(ch= #13)and(n=5)or(ch= #27);
textattr:=7;
clrscr;
end.

case ch of 
#13: case no of