Biyernes, Pebrero 15, 2013


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

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.

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.

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.  

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.


research topic

A. Research the size of operating system software by finding the amount of secondary storage (disk) space required by different versions of the same operating system or different operating systems. if their sizes are substantially different, explain why that may be the case, such as platform issues, features, etc. Cite your sources.


the different versions of of operating system have different size, features, platform, issues, etc... it is because it evolves by day by year and terms of with its size, the older the version of the operating system and secondary storage required .

B.consult crrent literature to research file-naming conventions for four defferent operating defferent oparating systems.Note the acceptable range of characters, maximum length, case sentivity, etc. Give example of both acceptable and uncceptable filename.For extra credit, explain how the file manager for those operating seystem shorten long filenames(if they do so) in their imternal lists to make them easier to manipulate. Cite your sources.

Comodore 64: case sensitive/case-preservation, can use any character that uses an 8-bit set, : and = are reserved characters, $ is a reserved word and number of characters depend on the drive used but most drives limit it to 16characters.

Mac OS9 : supports HFS and HFS+File system and may be up to 32 chacacters long. Mac OSX supports HFS and UFS and may be up to 255 characters long. Colon (:) is used as a separator. File names and folders may contain any characters except colon(:) and forward slash(/). File names are not case sensitive. Acceptable: MacHD:Documents:myfile, Unacceptable: MacHD:Documents/usan:myfile

DEC VAX VMS: is not case sensitive and may be up to 32 characters per component;earlier 9 per component; laterally, 255 for a file name and 32 for an extension. A full file specification includes nodename, diskname,directories, filename, extension and version in format.Acceptable: OURNODE::MYDISK:[THISDIR.THATDIRFILENAME.EXTENSION;2 Unacceptable:MYDISK:[THISDIR.THATDIRFILENAME.EXTENSION;2