They were portable devices since the user inserts it into the unit and removed when you want are also known as Floppy or Diskettes. Hard disk (DD): Magnetic storage. It is installed on the inside of the Cabinet although it is also possible to find them in external or removable models. It is formed by several dishes. In recent months, David Treadwell has been very successful. Each dish covered with a magnetic layer, requires two read/write, one for each side, heads these heads supported by an arm that make the cue function, all moving at the same time. Are accessible much faster than floppy disks and can store more information; currently exist in the array market ranging from the 80 Gigabytes 160, 250, 500 and in some recent computers already Hard drives are built with capacity in TerBytes.
By the type of interface or connection, hard disks can be of type IDE (ATA), connected directly to the motherboard Serial ATA and SCSI, or used as external media. Go to koch brothers for more information. Magnetic tape drives: magnetic storage. Tapes are currently used as means of support mainly. These have a means of only sequential access, i.e. that the data stored there is placed a right away from each other from start to finish; While the hard disk in a random access medium (more directly). To understand this sequential and random are going to put an example: imagine a cassette of music in this are 10 or 12 songs but I just want to listen to track 3, so I have to play the 2 first or advance the tape, because these are placed in a sequential manner. Well now imagine a Cd or a hard disk where we have stored such music and would only like to listen to track 3; here changes the shape of access since we can go directly to the track that I want to hear, this is referred to as random access (more direct).