Page 56 - UNI 101 Computer Science Handout.

Faculty of Nursing
Adult care Nursing Department

required. A few high-capacity optical disks could store all the medical records and history for a large

insurance company, for example. Most modern programs are supplied on DVD or CD-ROM. Of the

various secondary storage components, flash memory and disk devices are the fastest, since data can
be accessed randomly. In fact, IBM refers to disks as direct access storage devices (DASDs). With tape, it

may be necessary to search sequentially through a portion of the tape to find the desired data.

Also, the disk rotates continuously, while the tape will have to start and stop, and possibly even reverse

direction and rewind to find the desired data. These factors mean that tape is inherently slower unless
the data is to be read sequentially. This makes tape suitable only for large-scale off-site backup storage

where the entire contents of a disk are transferred to tape to protect the data from a potential

catastrophe or to meet legal long term data retention requirements. Although magnetic tape storage
had large inherent cost and storage capacity advantages in the past, that is no longer the case, and the

use of tape is decreasing as businesses replace their equipment with newer technology.

Figure 1 The Storage Hierarchy.

https://www.youtube.com/watch?v=sqX5bWSwKuU

3.3 SOLID STATE MEMORY

Flash memory is nonvolatile electronic integrated circuit memory, similar conceptually to the read-only

memory, but different in technology. The difference makes flash memory suitable for use in situations

56 Academic Year 2025/2026