Compare between the (Single level Directoryand, two level Directory) with Drawing and, Giveone example for each one of them?Logical structure of a directory:1) Single-Level DirectoryThe simplest directory structure is the single-level directory. All files are contained inthe same directory, which is easy to support and understand.A single-level directory has significant limitations, however, when the number of filesincreases or when the system has more than one user. Since all files are in the samedirectory, they must have unique names. If two users call their data file test.txt, thenthe unique-name rule is violated. For example, in one programming class, 23 studentscalled the program for their second assignment prog2.c; another 11 called it assign2.c.Fortunately, most file systems support file names of up to 255 characters, so it isrelatively easy to select unique file names.Even a single user on a single-level directory may find it difficult to remember thenames of all the files as the number of files increases. It is not uncommon for a user tohave hundreds of files on one computer system and an equal number of additionalfiles on another system. Keeping track of so many files is a daunting task.directory cafboatestdata mail conthex recordsatACCfiles2) Two-Level DirectoryAs we have seen, a single-level directory often leads to confusion of file namesamong different users. The standard solution is to create a separate directory for eachuser.In the two-level directory structure, each user has his own user file directory (UFD)The UFDs have similar structures, but each lists cely the files of a single user. When auser job starts or a user logs in, the system's master file directory (MFD) issearched. The MFD is indexed by user name or account number, and each entrypoints to the UFD for that user.When a user refers to a particular file, enly his own UFD is searched. Thus, differentusers may have files with the same name, as long as all the file names within eachUFD are unique. To create a file for a user, the operating system searches only thatuser's LFD to ascertain whether another file of that name exists. To delete a file, theoperating system confines its search to the local UFD; thus, it cannot accidentallydelete another user's file that has the same name.directory ser2 user user 4user flecat bo a testadats adirectory cattest x dataC C O O C O O Ó Ć CThe user directories themselves must be created and deleted as necessary.A special system program is run with the appropriate user name and accountinformation. The program creates a new UFD and adds an entry for it to the MFD.The execution of this program might be restricted to system administrators. Althoughthe two-level directory structure solves the name-collision problem, it still hasdisadvantages. This structure effectively isolates one user from another. Isolation is anadvantage when the users are completely independent but is a disadvantage when theusers want to cooperate on some task and to access one another's files. Some systemssimply do not allow local user files to be accessed by other users.If access is to be permitted, one user must have the ability to name a file in anotheruser's directory. To name a particular file uniquely in a two-level directory, we mustgive both the user name and the file name. A two-level directory can be thought of asa tree, or an inverted tree, of height 2. The root of the tree is the MFD. Its directdescendants are the UFDs. The descendants of the UFDs are the files themselves. Thefiles are the leaves of the tree. Specifying a user name and a file name defines a pathin the tree from the root (the MFD) to a leaf (the specified file). Thus, a user name anda file name define a path name. Every file in the system has a path name. To name afile uniquely, a user must know the path name of the file desired.a

A Directory is the collection of the correlated files on the disk. In simple words, a directory is…

Answered: Compare between the (Single level…

Compare between the (Single level Directory and, two level Directory) with Drawing and, Give one example for each one of them?

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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