extract and verify

[mohfa]

Hello :

Const Head:String='BTR';

Var
S:String ;
Begin
S:='myfirstfile.doc';

end;

So what i want is :

to verify that the S always starts with 'BTR' i mean like

if not (S) starts with ('BTR') then exit else Continue .


S:=BTRmyfirstfile.doc =True
S:=myfirstfile.doc =false

and i want to be sure the file name contains only A..Z or 0..9 so only letters and numbers .

How could i do like this verification .


Thank you