The core infrastructure of any modern Radiology department is made up of computers/computer workstations and the connectivity or networking capability between these devices. All transactions between modalities, PACS, scheduling, billing, dictation, and reporting systems are made possible through specialized computer programs or applications that are executed by computers. Computer systems are quite diverse and are often designed to augment a specific task, whether it is to support image reconstruction for a modality such as computed tomography (CT) or digital radiography (DR) or rapid image display as in PACS. Fundamentally, all computers are built around a similar base design with enhancements in specific areas to address certain needs such as rapid storage access and data transfer for fileservers and improved video characteristics for PACS client display stations. The purpose of this chapter is to familiarize the reader with the fundamentals of computer architecture, networking, and computer applications.