From registers to files

Schools once kept attendance and student details in manual registers. That caused problems: entering data was tedious; the same detail written in different places could disagree; registers could be lost or damaged; and totals and percentages were worked out by hand, with errors.

Computers improved this with files. A file is a container that stores data; to use the data, we need programs that read and write it. But keeping data in separate files has its own limitations:

• Difficulty in access: a new program must be written for every new kind of question.
• Data redundancy: the same data is stored in many files. For example, a student's name (SName) is kept in both the STUDENT file and the ATTENDANCE file, and the same guardian's details are stored twice for two siblings.
• Data inconsistency: if a name is changed in one file but not in the other, the files disagree.
• Data isolation: there is no link between related files, so combining their data is hard.
• Data dependence: the programs depend on the exact structure of each file; if the structure changes, every program that uses it must be changed.
• Controlled data sharing: it is hard to give different users different access rights. For example, guardians should be able to read attendance, but not change it.

The root problem is duplicated data, because duplicated data soon becomes mismatched data. A database management system solves these problems.