(c) The support of primitives for manipulating files and directories

(c) The support of primitives for manipulating files and directories;

(d) The mapping of files onto disk storage;

(e) Backup of files on stable (non volatile) storage; and

(f) Protection and security of the files.

Protection

• refers to a mechanism for controlling the access of programs, processes, or users to the resources defined by the computer together with some means of enforcement.
• Protection can improve reliability by detecting latent errors at the interfaces between component subsystems.
• An unprotected resource cannot defend against use (or misuse) by an unauthorised or incompetent user.

Command Interpretation

• One of the most important components of an operating system is its command interpreter.
• It is the primary interface between the user and the rest of the system.
• This program is variously called:
• The command line interpreter (CLI)
• The shell (in Unix)

Summary

• The Figure depicts the role of the operating system in coordinating all the functions.

OS Structure

• We can view an OS from several vantage points i.e.
• Services that the system provides
• The interface that it makes available to users and programmers
• Its components and their interconnections.

OS Structure Overview

Operating System Services

• The common services provided by an OS are:
• Program execution
• OS loads a program into memory and executes the program
• The program must be able to end its execution, either normally or abnormally
• I/O Operation
• A program may require an I/O device while running
• Therefore an OS must be able to provide the required I/O
• File System Manipulation
• Programs need to read or write files.
• The OS gives permission to the program to operate on files.