MECH 2301 Lecture 15: MECH 2301 Lecture 15 Notes
20 May 2018
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MECH 2301 Lecture 15 Notes
Introduction
Psychical Course of Action
• The file manager checks the validity of the requests and then translates the requests
into the appropriate physical course of action.
• The directory system assists in the location and organization of the file.
• When required, the file manager makes specific I/O data transfer requests to the I/O
device handler layer for execution of the transfer.
• Upon completion of the request, the directory is updated, if necessary, and control is
returned to the command shell or program.
• A general view of the process is illustrated
• As a specific example of this process, consider what occurs within the operating system
when the user of a typical system types the command COPY D: \FILEX TO C:
• Moves the FILEX icon with a mouse to the C
• Drawer on a system with a graphical command interface—the operation is the same
• The sequence of steps takes place.
• Although this description seems long, the steps are reasonable and should not be too
difficult
• The command interface interprets the command and determines that a copy of FILEX on
device D: is to be made and stored on device C:
• The command shell passes the request to the file manager.
• Typically, the shell will request that the file manager open FILEX on D: and create FILEX
on C:
• The file manager looks in the directory for device D: to find a file named FILEX.
• If it succeeds, the file manager reserves a block of space in memory, called a memory
buffer, large enough to hold one or more physical blocks of data from the file.
• Next, the file manager looks in the device C
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