MECH 2301 Lecture Notes - Lecture 20: Device Driver
20 May 2018
School
Department
Course
Professor
MECH 2301 Lecture 20 Notes
Introduction
Different Methods of File Access
• The file management system supports manipulation of the data within the file.
• For some systems, it can identify, locate, and manipulate individual records or individual
blocks within a file, possibly for several different methods of file access.
• For others, the manipulation is limited to reads, writes, and the movement of a pointer.
• The file management system acts as an interface for the transfer of data to and from the
various I/O devices by requesting transfers from the I/O device driver level of the
operating system.
• It also assigns buffer spaces in memory to hold the data being transferred.
• The actual transfer, and the interface between the physical device and the operating
system, is handled by the appropriate I/O device driver.
• The file system manages file security and protection.
• It attempts to protect the integrity of files and prevent corruption. It provides a
mechanism to control access to files.
• There are several different types of access control in use.
• Summing up the operation, the file manager receives requests from the utility/
command layer of the operating system or from application programs, determines the
course of action, and attempts to fulfill the request.
• In those cases that require data transfer to or from an I/O device, the file manager will
issue a request to the appropriate I/O device driver in the next inner layer to perform
the actual I/O transfer.
• The file manager specifies the physical block to be transferred, the direction of the
transfer, and the memory location to be used, but the actual transfer is performed by
the I/O device driver.
• There are two powerful advantages in separating the file and I/O functions into different
tasks.
find more resources at oneclass.com
find more resources at oneclass.com
