Warming up (Exercice Conversion De Base)

{https://cdn.discordapp.com/attachments/440593885740269568/831246181837307955/image0.jpg}
Program revision2;
Uses Wincrt;
Var
  f: Text;

Function premier (ch:String): Boolean;
Var
  r,n,e,i: Integer;
Begin
  Val (ch,n,e);
  r := 0;
  For i:=1 To n Do
    If n Mod i=0 Then
      r := r+1;
  premier := r=2;
End;

Function convert_2(ch:String): String;
Var
  c: String;
  n,e: Integer;
Begin
  Val (ch,n,e);
  ch := '';
  Repeat
    Str (n Mod 2,c);
    ch := c+ch;
    n := n Div 2;
  Until (n=0);
  convert_2 := ch;
End;

Function convert16 (ch:String): String;
Var
  c: String;
  n,e: Integer;
Begin
  Val (ch,n,e);
    writeln (ch);
    ch:='';
  Repeat
    If (n Mod 16)>=10 Then
      Begin
                ch := Chr(55+n Mod 16)+ch;
        n := n Div 16;
      End
    Else
      Begin
        Str (n Mod 16,c);
        ch := c+ch;
        n := n Div 16;
      End;
  Until n=0;
  convert16 := ch;
End;

Function comptage0 (ch:String): Integer;
Var
  r,i: Integer;
Begin
  r := 0;
  For i:=1 To Length(ch) Do
    If ch[i]='0' Then
      r := r+1;
  comptage0 := r;
End;

Function valide (ch:String): Boolean;
Var
  ch1,ch2,ch3: String;
Begin
  ch1 := Copy (ch,1,3);
  ch2 := Copy (ch,4,5);
  ch3 := Copy (ch,9,5);
  If (premier (ch1)) And (comptage0(convert_2(ch2))>8) And ((Pos('E',convert16(ch3))<>0) Or (Pos('F'
     ,
     convert16(ch3))<>0) Or (Pos('D',convert16(ch3))<>0)) Then
    valide := True
  Else
    valide := False;
End;

Procedure traitement (Var f:Text);
Var
  ch: String;
Begin
  Reset (f);
  While Not (Eof (f)) Do
    Begin
      Readln (f,ch);
      If valide (ch) Then
        Writeln (ch,': code valide')
      Else
        Writeln (ch,': code déjà utilisé');
    End;
  Close (f);
End;
Begin
  Assign (f,'c:\bac\code.txt');
  traitement (f);
End.