To conduct economic activity, to pursue science and art, data carriers were required for the person at all times. For this purpose various materials and devices were used. The choice of concrete data carriers was defined by availability of materials and the level of development of technologies.
From the history of development of data carriers
During an era of formation of human society cave walls were enough for people to record information necessary to them. Such "database" entirely would go in yes to the flash card the size in megabyte. However for the last several tens of thousands of years the volume of information with which the person is forced to operate significantly increased. Now for data storage disk stores and cloud storages of data are widely used.
It is considered that the history of data recording and its storage began about 40 thousand years ago. The surfaces of rocks and a wall of caves kept images of representatives of fauna of a late paleolith. Much later plates from clay became current. Could apply images to the surfaces of such ancient "tablet" of people and make entries by means of the pointed stick. When the clay structure dried, record was fixed on the carrier. The lack of a clay form of storage of information is obvious: such plates differed in fragility and fragility.
About five thousand years ago in Egypt began to use more perfect data carrier – papyrus. Data brought on special sheets which were produced from specially processed plant stalks. This type of data storage was more perfect: sheets of papyrus of easier clay tablets, it is much more convenient to write on them. This type of storage of information lived in Europe till the 11th age of a new era.
In other part of the world – in South America – smart Inca invented the nodular letter meanwhile. Information in this case was fixed by means of knots which in a certain sequence were tied on thread or a rope. There were whole "books" from small knots where data on population of the empire of Inca, on tax levies, economic activity of Indians were fixed.
Subsequently paper became the main data carrier on the planet for several centuries. It was applied to printing of books and mass media. At the beginning of the 19th century the first punched cards began to appear. They were done of dense cardboard. These primitive machine data carriers began to use widely for the mechanical account. They found application, in particular, when carrying out population censuses, used them also for control of weaving looms. The mankind came very close to a technological breakthrough which occurred in the 20th century. Mechanical devices were succeeded by the electronic equipment.
What is data carriers
All material objects are capable to bear in themselves any information. It is considered to be that data carriers are allocated with material properties and reflect certain relations between reality objects. Material properties of objects are defined by characteristics of substances from which carriers are executed. Properties of the relations are depending on qualitative features of processes and fields by means of which data carriers are shown in a material world.
In the theory of information systems it is accepted to subdivide data carriers by origin, to a form and the size. In the simplest case the data carriers divide on:
- local (for example, hard drive of the personal computer);
- alienated (removable diskettes and disks);
- distributed (communication lines can be considered as them).
The last look (communication channels) can be considered under certain conditions both data carriers, and Wednesday for its transfer.
In the most general sense objects, different in the form, can be considered as data carriers:
- paper (books);
- plates (photographic plates, gramophone records);
- films (photo, film);
- audio cassettes;
- microforms (microfilm, microfiche);
- videotapes;
- compact disks.
Many data carriers are known since ancient times. These are stone plates with the images applied to them; clay tablets; papyrus; parchment; birch bark. There were other artificial data carriers much later: paper, different types of plastic, photographic, optical and magnetic materials.
Information is brought on the carrier by means of change of any physical, mechanical or chemical properties of a working environment.
General information about information and ways of its storage
Any natural phenomenon is anyway connected with preservation, transformation and information transfer. It can be discrete or continuous.
In the most general sense the data carrier is a certain physical environment which can be used for registration of changes and accumulation of information.
Requirements to artificial data carriers:
- high density of record;
- possibility of numerous use;
- high speed of reading of information;
- reliability and durability of data storage;
Separate classification is developed for the data carriers used in electronic computer systems. Carry to such data carriers:
- tape carriers;
- disk carriers (magnetic, optical, magnetooptical);
- flash drives.
Such division has conditional character and is not exhaustive. By means of special devices on the computer equipment it is possible to work with traditional audio- and videotapes.
Characteristics of separate data carriers
At the time the greatest popularity was received by magnetic data carriers. Data in them are presented in the form of sites of a magnetic layer which is applied on the surface of the physical carrier. The carrier can have an appearance of a tape, card, reel or disk.
Information on the magnetic carrier is grouped in zones with intervals between them: they are necessary for high-quality record and data read-out.
Data carriers of tape type are used for backup and data storage. They are a magnetic tape with a capacity up to 60 GB. Sometimes such carriers have an appearance of tape cartridges considerably of bigger volume.
Disk data carriers can be rigid and flexible, replaceable and stationary, magnetic and optical. They have usually the form of disks or diskettes.
The magnetic disk has an appearance of a plastic or aluminum flat circle which is covered with a magnetic layer. Fixing of data on such object is carried out by the magnetic record. Magnetic disks are figurative (replaceable) or non-replaceable.
Floppy disks (floppy disks) have the volume of 1.44 MB. They are packed about special plastic cases. Otherwise such data carriers call diskettes. Their appointment – temporary storage of information and data transfer from one computer on another.
The hard magnetic drive is necessary for permanent storage of data which are often used in work. Such carrier is a package of their several disks linked among themselves concluded in the strong tight building. In use the hard drive is often called "winchester". Capacity of such store can reach several hundred GB.
The magnetooptical disk is the data carrier placed in the special plastic envelope called the cartridge. This universal and very reliable receptacle of data. Its distinctive feature – the high density of the stored information.
The principle of data recording on the magnetic carrier
The principle of data recording on the magnetic carrier is based on use of properties of ferromagnetics: they are capable to keep magnetization after removal of the magnetic field operating on them.
Magnetic field is created by the corresponding magnetic head. During record the binary code takes the form of an electric signal and moves on a head winding. When current proceeds through a magnetic head, around it magnetic field of a certain tension is formed. Under the influence of such field in the core the magnetic flux is formed. Its power lines become isolated.
Magnetic field interacts with the data carrier and creates in it a state which is characterized by some magnetic induction. When the impulse of current stops, the carrier keeps the condition of magnetization.
To reproduce record, use the reading-out head. Magnetic field of the carrier becomes isolated via the head core. If the carrier moves, the magnetic flux changes. The reproduction signal comes to the reading-out head.
One of important characteristics of the magnetic data carrier – record density. It is in direct dependence on properties of the magnetic carrier, type of a magnetic head and its design.