Exercises

1.Explain in your own words why file deallocation is important and what would happen if it did not accord on a regular basis
answer:

It really depends on the operating system. Most modern operating systems will deallocate all files assigned to a process when the process terminates, and will flush all internal I/O buffers prior to that, so closing files is mainly a question of neatness, not necessity.

Some bound I/O management libraries may retain internal application-side buffers that aren't flushed unless the file is explicitly closed. In these cases, you might need to close a file before terminating in order to avoid file corruption or lost updates. But that is relatively rare these days.

It's good form to close files explicitly, just in case they need to be closed explicitly. But you don't really have to do it in most cases. For "quick and dirty" development of small apps.

2.Describe how the File manager allocates a file to a single user . List the steps that you think would be followed and emplane your reasoning.
answer:

Best-fit: search the entire list of available memory and allocate the
    smallest block that is big enough.
Best-fit: search the entire list of available memory and allocate the .... If a file is moved from one environment to another, then it would become .... 13.2 Consider the following I/O scenarios on a single-user PC. ... Would you use polled I/O, or interrupt-driven I/O? Give reasons for your choices.

3.Is device independence important to the file manager ? Why or why not ? describe the consequences if that were not the case.
 answer:

The device independence is important to a file manager  because with out the independence where the file well be stored if he wont depend on a storage. If there where  no independence to the file manager the file cant be manage. 

4.Do you think file retrieval is different on a menu-driven system  and a command-driven system? Explain your answer and describe your difference between the two. Given an example when each would preferred over the other.  
 answer:

command driven

Refers to programs and operating systems that accept commands in the form of special words or letters. In contrast, programs that allow you to choose from a list of options in a menu are said to be menu driven. Command-driven software is often more flexible than menu-driven software, but it is more difficult to learn.
menu-driven system
An interactive computer system in which the operator requests the processing to be performed by making selections from a series of menus.

5.