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Chapter 6 - Chapter 6 F ile organization terms and concepts...

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Chapter 6 File organization terms and concepts 1. Computer system organize hierarchy Ω bits represents the smallest unit of data a computer can handle a group of bits Ω bites represents a single character, which can be a letter, a number or another symbol groups to from Ω fields a grouping of characters into a word, a group of words, or a complete number e.g. a person's name or age groups to from Ω records a group of related fields e.g. the student's name, the course taken, the date groups to from Ω files a group of records of the same type groups to from Ω databases a group of related files ----------------------------------------------------------------------------------------------------------------- Ω entity a person, place, thing, or event on which we store and maintain information descried by record also decried by attribute 2. Problems with the traditional file environment Ω data redundancy and inconsistency data redundancy the presence of duplicate data in multiple data files so that the same data are stored in more than place or location occurs when different groups in an organization independently collect the same piece of data and store it independently of each other. waste resources and lead to Each characteristic or quality describing a particular entity e.g. Student_ID is attributes of the entity Course
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data inconsistency the same attribute may have different values additional confusion might result from using different coding systems to represent values for an attribute cause Ω program-data dependence refers to the coupling of data stored in files and the specific programs required to update and maintain those files such that changes in programs require changes to the data any changes in a software program could require a change in the data accessed by that program Ω lack of flexibility a traditional file system can deliver routine scheduled reports after or respond to unanticipated information requirements in a timely fashion Ω poor security because there is little control or management of data, access to and dissemination of information may be out of control no way of knowing who is accessing or even making changes to the organization's data Ω lack of data sharing and availability because pieces of information in different files and different parts of the organization cannot be related to one another, it is virtually impossible for information to be shared or accessed in a timely manner information cannot flow freely across different functional areas of different parts of the organization The database approach to data management 1. Database management systems Ω definition software that permits an organization to centralize data, manage them efficiently and provide access to the stored data by application programs Ω acts as an interface between application programs and the physical data files Ω relieves the programmer or end user from the task of understanding where
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