MECH 2301 Lecture Notes - Lecture 21: Device Driver, Management System
20 May 2018
School
Department
Course
Professor
MECH 2301 Lecture 21 Notes
Introduction
Logical file access methods
• The idea of changing an I/O device driver is familiar to you if you have ever installed a
new printer, video card, or disk drive for your PC.
• A command request to redirect data is easy to implement
• Since the file manager controls the file.
• The file manager simply directs the binary data to a different I/O driver.
• In general, the file manager is responsible for
• Assumes the chore of, organizing, locating, accessing, and manipulating files and file
data and managing space for different devices and file types
• The file manager takes requests as its input, selects the device, determines the
appropriate format, and handles the request.
• It uses the services of the I/O device layer to perform actual transfers of data between
the devices and memory.
• There are a number of different ways in which to access the data in a file.
• The method used reflects both the structure of the file and the way in which the data is
to be used.
• For example, a program file made up of executable code will be read as a whole into
memory.
• A file made up of inventory data records will often be accessed one record at a time, in
some random order queried to the system.
• As we have already seen, some file management systems support a number of different
formats
• While others leave the structuring and formatting of data within a file to the application
programs and utilities that use the file
• It is beyond the scope to discuss file access methods in any detail.
find more resources at oneclass.com
find more resources at oneclass.com
