A Textbook of Data Structures and Algorithms, Volume 3

14File Organizations

14.1. Introduction

The main component of a computer system is the memory, also referred to as the main memory or the internal memory of the computer. Memory is a storage repository of data that is used by the CPU during its processing.

When the CPU has to process voluminous data, the computer system has to take recourse to external memory or external storage to store the data, due to the limited capacity of the internal memory. The devices which provide support for external memory are known as external storage devices or auxiliary storage devices.

Given that the main memory of the computer is the primary memory, the external memory is also referred to as secondary memory and the devices as secondary storage devices. Examples of secondary storage devices are magnetic tapes, magnetic disks, drums, floppies, USB flash drives and so forth. While the internal memory of a computer system is volatile, meaning that data may be lost when the power goes off, secondary memory is nonvolatile.

Each of the secondary storage devices has its distinct characteristics. Magnetic tapes, built on the principle of audio tape devices, are sequential storage devices that store data sequentially. On the other hand, magnetic disks, drums, floppy diskettes and USB flash drives are random access storage devices that can store and retrieve data both sequentially and randomly. Random-access storage devices are also known as direct access storage devices. Section 18.2 elaborately discusses ...