What is DBMS and its history?

How Computer Data is Stored and used?
There're 3 ways that data can be stored and used: 1. Magnetic storage. When the data is read/write, the head of the storage device pass the surface of the disk to read the magnetic field alignment and thus the data. 2. Optical storage. The surface of the disk has spots that reflect light, which are interpreted as a binary '1', and spots that do not reflect light, interpreted as a binary '0'. They're removable and convinience. 3. Magneto-optical storage. It uses both magnetic and optical technologies to produce disks with a large capacity. It uses laser beam, which is focused on the spinning disk while a sensor detects changes in polarisation of reflected light from the surface, to read the data.

In order to manage our data efficiently, we need to know more about DBMS and its history.
DBMS which stands for database management system is computer software that manages databases. Databases have been in use since the earliest days of electronic computing.

The system has been developing for 4 decades. By the mid-1960s, there're many similar systems were used in commerce. At that time, people were thinking about a standard. A group which was founded by Charles Bachman, create and standardization of COBOL.

In 1971, they released their standard"Codasyl approach". This approach was based on manual operation. When the database was first opened, the program was handed back a link to the first reocrd in the database, which also contained pointers to other pieces of data. To find any particular record, the programmer need to step through these pointers every time until the required record was returned. IBM also developed a DBMS system called IMS in 1968.

In 1970s, DBMS were developed to a relatonal DBMS from a navigational DBMS. Edgar Codd, who worked at IBM, wrote a new approach to contstruct the database. He used a "table" of fixed-length records. The realtional model solve the inefficient problem with optional elements being moved out of from the main table only if they're needed. In the relational model, some infromation was used as a "key" to define a particular record uniquely. Then Codd's ideas was picked up by Eugene Wond and Michael Stonebraket. They develop a projuect called "INGRES" . They use student programmers to produce code.

In 1979, the products of INGRES were ready for widespread use. At the same time, IBM begined to work with a prototype system based on Codd's concepts. It's called "System R". In1978 and 1979,a standarized query language,SQL, was added, and muliti-user version of the system was tested. In1980s, Sybase, informix, Nonstop SQL and Ingres were sold. In sweden, people also develop a Mimer SQL in the mid-70s. The project was introduced into the independent enterprice.

References
Some Speil (2004) How Computer Data is Stored: an Introduction
http://www.datamole.com/storage.php
Wikipedia (4 Apr 2009) Database management system
http://en.wikipedia.org/wiki/Database_management_system