计算机专业英语Chapter3 Database Fundamentals.ppt

计算机专业英语Chapter3 Database Fundamentals
Data storage traditionally used individual, unrelated files, sometimes called flat files. In the past, each application program in an organization used its own file. In a university，for example, each department might have its own set of files: the record office kept a file about the student information and their grades, the financial aid office kept its own file about students that needed financial aid to continue their education，the scheduling office kept the names of the professors and the courses they were teaching, the payroll department kept its own file about the whole staff (including professors), and so on.
Today, however, all of these flat files can be combined in a single entity, the database for the whole university.
Introduction to DBMS
Although it is difficult to give a universally agreed definition of a database, we use the following common definition: a database is a collection of related, logically, coherent data used by the application programs in an organization.
A database management system (DBMS) is an important type of programming system, used today on the biggest and the smallest computers. As for other major forms of system software, such as compilers and operating systems, a well-understood set of principles for database management systems has developed over the years, and these concepts are useful both for understanding how to use these systems effectively and for designing and implementing DBMS's. DBMS is a collection of programs that enables you to store, modify, and extract information from a database. There are many different types of DBMS's, ranging from small systems that run on personal computers to huge systems that run on mainframes.
Ⅰ.Components of DBMS
A DBMS is a combination of five components：hardware, software, data, users, and procedures .
1. Hardware
The hardware is the physical computer system that allows access to data. For example，the terminals, hard disk，mai