Mass memory

In Data-processing, a mass memory is a memory of great capacity, nonvolatile and which can be read by a computer.

Types of mass memories

Obsolete technologies:

Perforated card
Paper tape
Disc Zip of the company Iomega
Drum

Technologies of use:

Experimental technology:

holographic Memory

The distributed filesystems, the lans or waiters Internet are not really types of way but mass memory rather of reaching a mass memory. The mass memory used by the distributed filesystems, the lans or waiters Internet is usually the hard drive.

Essential attributes of a mass memory

the possibility of functioning in mode of writing and reading so that the user can write information then to read again them with the need.
the possibility of storing the information recorded even in absence of power supply.
an important storage capacity. The concept of important capacity varied in time. Today, it is not considered that a box of perforated cards or a Ruban perforated has an important capacity. On the other hand, at the beginning of data processing, one was impressed by the quantity of information which one could record there!.

Characteristics of a mass memory

average access time to information
the speed of transfer of information
the cost per million recorded bits
storage capacity

Principal uses of the mass memories

To record information to be able to treat them later. For example, to record the names of the employees of a company and their hourly salaries to produce the accounts - checks of pay of the employees.
To record information to preserve of it a backup copy if the principal copy would be lost.
To record information to transfer them towards another computer.

In the universe of the Microcomputer S, the mass memories most used for the preceding uses are:

the hard drive for information which will have to be treated later on;
CD and the DVD for the backup copies;
key USB for the transfer of information between microcomputers.

See too