Kristen Nygaard, 75, a pioneer in developing programming language for computers who helped lay the basis for the Internet, died of a heart attack Saturday in Norway. The University of Oslo professor was acclaimed internationally for his work in developing the programming language Simula that laid the basis for MS-DOS and the Internet. He and his colleague Ole- Johan Dahl, who died in June, were rewarded for their role in the invention of object-oriented programming at the Norwegian Computing Center from 1961 to 1967. Their work paved the way for the languages Java, C++ and others.