Magnetic tape is a sequential data storage medium. To read data, a tape drive must wind through the spool of tape to the exact location of the desired information. To write, the tape drive encodes data sequentially on the tape. Because tape drives cannot randomly access or write data like disk drives, and are thus much slower, they have been replaced as the primary storage device with the hard drive. The hard drive is composed of thin layers of rigid magnetic platters stacked on top of one another like records in a jukebox, and the heads that read and write data to the spinning platters resemble the arm of a record player.
Floppy disks are another common magnetic storage medium.
They offer relatively small storage capacity when compared to hard drives, but unlike hard drives, are portable. Floppy disks are constructed of a flexible disk covered by a thin layer of iron oxide that stores data in the form of magnetic dots. Magnetic storage medium, for all its advantages, only has a life expectancy of twenty years. Data can be stored on electronic medium, such as memory chips. Every modern personal computer utilizes electronic circuits to hold data and instructions.