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#### Credit Card Validation

Are you in need to validate a credit card? The following routine does some basic checking and returns the type of the credit card as a number - or use the const array to get the type of credit card by name. (E.g. 'Mastercard').

This code does not check that the credit card is actually valid, that it is good for a purchase or whether it belongs to a certain person. To accept any kind of orders, you need to do an address verification, combined with checking the expiration date.

The routine is still handy as an input validator on forms. You may download it here.  ```program CardTest; uses Dialogs, SysUtils; {\$R *.RES} const CardType : array [0..4] of string = ('Invalid', 'Amex', 'Visa', 'Mastercard', 'Discover' ); function Vc(C: string) : Integer; var Card : string; VCard : array [0..21] of Byte absolute Card; XCard : Integer; Cstr : string; y, x : Integer; begin Cstr := ''; FillChar(VCard, 22, #0); Card := C; for x := 1 to 20 do if (VCard[x] in [48..57]) then Cstr := Cstr+Chr(VCard[x]); Card := ''; Card := Cstr; XCard := 0; if not odd(Length(Card)) then for x := (Length(Card)-1) downto 1 do begin if odd(x) then y := ((VCard[x]-48)*2) else y := (VCard[x]-48); if (y>=10) then y := ((y-10)+1); XCard := (XCard+y) end else for x := (Length(Card)-1) downto 1 do begin if odd(x) then y := (VCard[x]-48) else y := ((VCard[x]-48)*2); if (y>=10) then y := ((y-10)+1); XCard := (XCard+y) end; x := (10-(XCard mod 10)); if (x=10) then x := 0; if (x=(VCard[Length(Card)]-48)) then Vc := Ord(Cstr)-Ord('2') else Vc := 0 end; begin ShowMessage(CardType[Vc('4479750100222862')]); end. ```  You don't like the formatting? Check out SourceCoder then!
Generated 12:02:10 on Aug 6, 2020