Tuesday, November 17, 2009

ASSIGN_01

Hierarchical refers to systems that are organized in the shape of a pyramid, with each row of objects linked to objects directly beneath it. Hierarchical systems pervade everyday life. The army, for example, which has generals at the top of the pyramid and privates at the bottom, is a hierarchical system.Hierarchical systems are as popular in computer systems as they are in other walks of life. The most obvious example of a hierarchical system in computers is a file system, in which directories have files and subdirectories beneath them. Such a file organization is, in fact, called a hierarchical file system . Many data structures for storing information are hierarchical in form. Menu-driven programs are also hierarchical, because they contain a root menu at the top of the pyramid and submenus below it. WHILE...

A relational database matches data by using common characteristics found within the data set. The resulting groups of data are organized and are much easier for people to understand.Such a grouping uses the relational model (a technical term for this is schema). Hence, such a database is called a "relational database."The software used to do this grouping is called a relational database management system. The term "relational database" often refers to this type of software.Relational databases are currently the predominant choice in storing financial records, manufacturing and logistical information, personnel data and much more.