Thread: External storage devices

Very to often need to store a certain amount of data more or less permanent. The memory of the computer is volatile and what is worse, scarce and expensive. So when we have to keep our data for some time we have to resort to systems of storage more economical even at the cost of which is slower.

During the history of computers have used several methods for storing various data. At first tape was used paper perforated, then cards punched. Then switched to magnetic media, starting with large rolls of tape open.

So far all external storage systems were sequential ie not allowed to access point exactly where they stored the information without first party from scratch and without having read all the information, to the point where it was that we were seeking.

With the tapes began what would eventually access random data. You could book part tape to store certain information about the status of the data, and add some marks to make it easier to locate.

But it was not until the advent of magnetic disk technology when it came to its broadest sense. On discs is easier to reach any point of surface soon as it reached the point of reading and writing using two physical coordinates. For a part of the read / write can be moved in the direction of the radius of the disc and second the disc spins constantly so any point on the disc passes the head in a relatively short time. This does not happen with the tapes where there is only a coordinate physical.

Currently hard drives have an enormous capacity and are very fast although still slow compared to the memory RAM. The case of the CD is somewhere in between. In fact they are sequential in the way of saving data each disk has only one data track recorded in a spiral. However, this system combined with some RAM memory, provides close access to hard disks