MODERN OPERATING SYSTEMS PREFACE 1 INTRODUCTION 1.1 WHAT IS AN OPERATING SYSTEM? 1.1.1 The Operating System as an Extended Machine 1.1.2 The Operating System as a Resource Manager 1.2 HISTORY OF OPERATING SYSTEMS 1.2.1 The First Generation (1945-55) Vacuum Tubes and Plugboards 1.2.2 The Second Gene