That would save space in the transaction file, but
now in order to compute a customer??™s bill, you must search serially through two files.
DATABASE TYPES
Starting in the late 1960s, database systems were developed to deal with these and other problems. Two early
types of databases were the hierarchical and networking types. IBM offered DL/1, a hierarchical database, and various
other hardware and software companies offered networking databases on the CODASYL (Conference On
DAta SYstems Language, Database Task Group) model. IDMS was a particularly successful CODASYL database.
The hierarchical and networking database structures organized files together to provide more rapid
access to the information, better security, and easier updates. However, the structures were complex, tied to the
implementation details of the file system, and fairly rigid.
In 1970, E. F. Codd (Edgar, ???Ted,??? an Englishman who moved to the US after serving in WWII) of IBM
proposed the relational database model. The relational model relied heavily on mathematical theory. At the
time, it may have sounded ???dreamy,??? as data were simply to be stored in tables (called ???relations???). Each relation/
table would maintain information about one entity type (type of thing), and entities would be related to one
another by virtue of information stored in the tables, rather than by external pointers or other devices.
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