In short, a mass storage device for computers that uses some form of magnetic tape to store data. While there are many shapes and forms of these devices, they share one common characteristic: they store data sequentially from the beginning to the end of a tape. Below, a few common types of tape drives are described.

Audio Cassette
Once the most common form of tape drive, at least for home users, was the breed that used standard audio cassette as the storage medium. Depending on the type of computer, you either used a dedicated device which typically had a special connection (such as the Datasette for the Commodore VIC 20) or a typical home cassette player (such as used on early Apple II computers) which would simply use 1/8th inch audio jacks.

The audio cassette "tape drive" in its many incarnations and definitions rarely featured much in the way of automation. More specifically, searching for the right position on the tape was a manual process of pressing the fast forward and rewind buttons. Hopefully the unit featured an index display, to see where on the tape you were positioned. In some configurations, the computer might have had the ability to start/stop the tape motor. This was useful because you could cue the tape to the right position for loading, press the play button, and the motor wouldn't start the tape until the computer was ready to load.

Random Access Tape Drives
This type of tape drive comes in many forms. You could have, for example, a DLT drive, which uses special cartridges with high quality digital tape inside, or even drives that can almost use regular audio cassettes (like the high speed digital tape drive on the Coleco ADAM).

The main difference between this type of drive and the standard audio cassette form is that it is random access meaning that the read/write/seek operations of the drive are controlled by the computer. However, these types of drives also offer much faster data transfer speeds than audio cassettes and also typically hold a much larger quantity of data.

In this category lies possibly the only still-in-production version of tape drive; tapes used for hard drive backup. One of the most popular types is DLT which holds several gigabytes of data.

The above writeup covers only the smaller tape drives associated with personal desktop computers. Mainframe systems used tape drives roughly the size and shape of caskets stood on end, which in turn used reel-to-reel tapes about the size of vinyl albums. That would be twelve inches in diameter, for you young punks who've never seen record albums. I haven't worked as a tape monkey for decades, so I have no idea whether tape drives are still huge and clunky (and the tapes likewise) or whether they've gotten smaller and more compact like everything else in the world of computers.

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