MECH 2301 Lecture 8: MECH 2301 Lecture 8 Notes
20 May 2018
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MECH 2301 Lecture 8 Notes
Introduction
Alphanumeric Unicode
• A data file consisting of alphanumeric Unicode characters representing records made up
of names, addresses, and accounting information applicable to a business database.
• A data file configured in some special way to represent an image, sound, or other
object.
• Several examples of these types of files were illustrated
• A directory file consisting of information about other files
• One common file representation views a file logically as a collection of records, each
made up of a number of fields.
• A typical record-oriented file is shown
• In this illustration, each record is made up of the same fields, and each field is the same
fixed length for all records
• These restrictions are not necessarily valid in all cases.
• Some fields may not be required for certain records.
• The company personnel file shown does not require the salary field for retired
employees.
• This file also uses a field of comments.
• The comments field is a variable-length field, so that more comments can be added
when necessary.
• This also shows that the file may appear differently, without affecting the record
structure underneath.
• The layout shown is sometimes called a table image
• While the layout in is referred to as a form image.
• Describing a file by its records and fields represents the file logically
• That is, it represents the file the way the user views it.
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