The document discusses different types of external memory storage technologies including magnetic disks, optical disks, and magnetic tape. It provides details on how read and write mechanisms work for magnetic disks using conductive coils and magnetic fields. It also describes the organization of data on disks including tracks, sectors, and constant angular velocity to optimize storage capacity and access times. Characteristics of different disk types like removable vs non-removable, fixed vs movable heads, and single vs multiple platters are outlined. Finally, it summarizes optical disk technologies like CD-ROMs and DVDs including capacities, speeds, read mechanisms, and advantages/disadvantages compared to magnetic disks.

3. Inductive Write MR Read

5. Disk Data Layout

7. Disk Layout Methods Diagram

12. Multiple Platters

13. Tracks and Cylinders

15. Timing of Disk I/O Transfer

17. CD Operation

24. CD and DVD