A library computer system is the software used to catalog, track circulation (where appropriate), and inventory a library's assets. It is intended for home, church, private enterprise, and other small- to medium-sized collections. Larger libraries typically use an integrated library system to manage the more-complex activities, such as acquisitions, interlibrary loan, and licensing online resources. With distributed software the customer can choose to self-install or to have the system installed by the vendor on their own hardware. The customer can be responsible for the operation and maintenance of the application and the data, or the customer can choose to be supported by the vendor with an annual maintenance contract. Some vendors charge for upgrades to the software. Customers, who subscribe to a web (hosted) service, upload data to the vendors remote server through the Internet and may pay a periodic fee to access their data. Modern libraries are constituted within and by a tradition of techniques and practices that represent a hundred years of codified professional knowledge. This book provides a historical overview of this tradition that created a complex environment of expectation and misunderstanding for introducing library automation. This book attempts to delineate and discuss the applications of the computer that have been behind the technological revolution of library science. The aim of the book is to mainly enhance the readers' understanding of the ways in which computers have heralded the invasion of technology into library science, with special attention to the emergence of digital libraries which promise to make libraries and their information completely at the mercy of our fingertips.