/* ************************************* */
/* Procedim  que  constroi o dig controlo*/
/*****************************************/


constroiisbn:=proc()

local i, isbn, teste, checksum;

begin
	isbn:=0:
	input("Indique o ISBN da forma [a,b,c,...] ",isbn):
	/* entrada dos 9 simbolos do ISBN */
	isbnArray:=array(1..9,isbn);
	teste:=0;
	for i from 9 downto 1 do
		teste:=teste+(11-i)*isbnArray[i]
	end_for:
	checksum:=-teste mod 11: /* checksum e' o digito de controlo */
	if checksum=10 then /* caso em que o caracter e' X=10 */
		print("O digito de controlo e' X")
	else print(" O digito de controlo e' ",checksum):
	end_if:
end_proc: