This chapter examines one of the most important uses of computers: the storage and retrieval of information. While the general organization of this book is “top-down,” working from end-user applications, down through the various levels of software, towards the physical hardware of the computer, the topic of information storage and retrieval will be approached in the opposite direction – from the physical hardware level to the end-user level.

Our discussion of information storage and retrieval focuses on four distinct “views” of the process, or “levels” at which it takes place: the hardware level, the file organization level, the programmer level, and the end-user level. These four views are illustrated in .

examines information storage and retrieval from the point of view of what happens at the hardware level. The discussion focuses on disk drives, which are the most popular form of mass storage device.

introduces the file concept and explores three different alternatives for storing files on disk. These alternative storage techniques are known as: contiguous, linked, and indexed storage.

looks at information storage and retrieval from the point of view of the application programmer. While details of the software development process, including programming, are deferred until later in the text, this section will give you a feel for how programmers manipulate data files.

Finally, examines how data appears to the end-user. The two most common end-user views of data are discussed: the view of the file system provided by the operating system, and the view of data provided by relational database systems. This second view will be explored in depth, due to the importance of relational database systems as end-user applications.