![]() They also keep the information stored on them when they are turned off. Disks are very slow compared with m em ory On the other hand, disks provide enormous capacity at much less cost than memory. This means that getting inform ation back from the library takes 5 million seconds, or almost 58 days. Given that our “m em ory access” takes 20 seconds, how long does the “disk access” to the library take, keeping the ratio the same as that of a real m em ory access and disk access? The disk access is a quarter of a million times longer than the m em ory access. Assume that accessing a disk is like sending to a library for the information you cannot find here in this book. Let’s say that this local, book-in-hand access takes 20 seconds. Assume that m em ory access is like finding something in the index of this book. To understand the size of this difference, we need an analogy. Getting the same information from a typical disk m ight take 30 milliseconds, or 30 thousandths of a second. How slow? The time it takes to get inform ation back from even rela tively slow electronic random access m em ory (RAM) is about 120 nanoseconds, or 120 billionths of a second. However, relative to other parts of a computer, disks are slow. Only a few years ago, disks with that kind of capacity looked like small washing machines. They are also technological marvels: one can pack th o u sands of megabytes on a disk that fits into a notebook computer. The Heart of File Structure Design Disks are slow. The Heart of File Structure Design A Short History of File Structure Design A Conceptual Toolkit: File Structure Literacy An Object-Oriented Toolkit: Making File Structures Usable Using Objects in C++ ♦> Introduce classes and overloading in the C++ language.Ĭhapter 1 Introduction to the Design and Specification of File StructuresĬ HA P T E R O U T L I N E 1.1 1.2 1.3 1.4 1.5 ♦> Discuss the need for precise specification of data structures and operations and the development of an object-oriented toolkit that makes file structures easy to use. ♦> Introduce the notions of file structure literacy and of a conceptual toolkit for file structure design. ♦> Survey the history of file structure design, since tracing the developments in file structures teaches us much about how to design our own file structures. Introduce the primary design issues that characterize file structure design. File Structures An Object-Oriented Approach with C++ Michael J. ![]()
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