International Bank Account Number

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The International Bank Account Number (IBAN) is an international standard for numbering bank accounts. It is ISO 13616 standard. The IBAN consists of up to 34 alphanumeric characters, comprising a country code, two check digits and a detailed bank account-number.

The country code using ISO 3166-1 alpha-2. The check digits calculated according to ISO 7064 (MOD97-10)

Function IsValidIban

Function IsValidIban checks is International Bank Account Number valid. Function StrMOD97 you find here ISO_7064#Function StrMOD97

function ReplaceLetterWithNumbers ( a_char:char):string;
var
  i: integer;
begin
  i := ord( upcase( a_char ) ) - ord( 'A' ) + 10;
  result := IntToStr( i );
end;   

function IsValidIban( s:string): boolean;
var
  a_char: char;
  s1: string;
  i : integer;
begin
  s := DelSpace( s );
  s1 := copy( s, 1, 4);
  delete(s, 1, 4);
  a_char :=  s1[1];
  delete(s1, 1, 1);
  s := s + ReplaceLetterWithNumbers ( a_char ) ;
  a_char :=  s1[1];
  delete(s1, 1, 1);
  s := s + ReplaceLetterWithNumbers ( a_char ) ;
  s := s + s1;
  i := StrMOD97( s );
  Result := i = 1;
end;