Ошибка чтение с диска 100

uses crt;
type
  tfile = file of char;
  mas = array ['a'..'z'] of integer;
  var f1: tfile;
    f2:text;
    a: mas;
    c:char;
    s:byte;
    f3,f4:file;
    
procedure readfile(var f1: tfile; var a: mas;var s:byte);
var c:char;
begin
s:=0;
assign(f1,'text.txt');
{$I-}
reset(f1);
{$I+}
if IOResult=0 then
 begin
  while not eof(f1) do
   begin
    read(f1, c);
    if c in ['a'..'z'] then inc(a[c]);
   end;
  close(f1);
 end
else
 begin
  writeln('File with text dont found');
  s:=1;
  exit;
 end;
end;
 
procedure maxsymb(var f1:text;a:mas);
var c:char;
    maxCnt: integer;
begin
assign(f1,'output.txt');
rewrite(f1);
maxcnt := 0;
for c:='a' to 'z' do
if a[c] > maxcnt then maxcnt:=a[c];
for c:='a' to 'z' do
if a[c]=maxcnt then
 begin
  writeln('Letter ', c, ' meets ', a[c], ' times');
  writeln(f1,'Letter ', c, ' meets ', a[c], ' times');
 end;
close(f1);
writeln('Date was record in file "output"');
end;
 
function ComparisonF (var f3, f4: file): boolean;
var
i, j: byte;
CF: boolean;
begin
Assign(f3,'text1.txt');
Assign(f4,'text2.txt');
reset(f3);
reset(f4);
CF:=false;
if FileSize (f3) <> FileSize (f4) then ComparisonF := false
else
  begin
  CF := true;
  while not (eof (f3)) and CF do
    begin
      BlockRead (f3, i, 512);
      BlockRead (f4, j, 512);
      CF := i = j;
    end;
    ComparisonF := CF;
  end;
  writeln(CF);
end;
 
 
begin
clrscr;
writeln('This program determines which letter is most often found in the file');
writeln('file.txt located on the C drive, press any key to continue');
readkey;
writeln;
readfile(f1,a,s);
if s=0 then maxsymb(f2,a);
writeln('Are the file the same size?');
ComparisonF(f3,f4);
writeln('The program has finished its work, press any key ...');
readkey;
end.

for i:=1 to 20 do//или другое четное число
 begin
  c:=chr(97+random(26));// c:char;
  write(f,c);
 end;

const
  maxSize = 100;
  f1Name = '1.txt';
  f2Name = '2.txt';
var
  f1, f2 : File;
  b1, b2 : array [1..maxSize] of Byte;
  count1, count2, i, cicle : Integer;
  NoMore : Boolean;
begin
  Assign(f1, f1Name); Reset(f1);
  Assign(f2, f2Name); Reset(f2);
  NoMore := False;
  cicle := 0;
  if FileSize(f1) <> FileSize(f2) then
    WriteLn('Размер?')
  else
    begin
      WriteLn('Размер одинаковый.');
      repeat
        Inc(cicle);
        BlockRead(f1, b1, maxSize, count1);
        BlockRead(f2, b2, maxSize, count2);
        WriteLn('Считано ', count1, ' и ', count2);
 
        for i := 1 to maxSize do
          if b1[i] <> b2[i] then
            begin
              WriteLn('Различие в ', i + pred(cicle) * maxSize,' : ', b1[i], ' - ', b2[i]);
              NoMore := True;
              Break;
            end;
 
      until (count1 = 0) or NoMore;
 
      if Not NoMore then
        WriteLn('Идентичны!');
    end;
  Close(f1); Close(f2);
end.