This chapter presents the rudiments of data storage within digital computers. It introduces the basics of digital circuitry and how a simple flip-flop can be used to store a single bit. It then discusses addressable memory cells and mass storage systems (magnetic disk, compact disks, and magnetic tape). Having established this background, the chapter discusses how information (text, numeric values, images, and sound) are encoded as bit patterns. The optional sections delve more deeply into these topics by presenting the problems of overflow errors, truncation errors, error detection and correction techniques, and data compression.