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Sunday, April 14, 2013

What are different components of operating system? – Part 5

10. Networking: 
- Presently, many different types of protocols along with applications and hardware for using them are supported by most of the operating systems. 
The computers running different operating systems can easily become a part of the network and participate in resource sharing activities such as sharing of printers, scanners and of course files. 
- They may connect to network either through wired connection or a wireless one. 
- Through this component, OS of one computer system can access the resources of another computer system at a remote location. 
- Almost anything can be shared including remote computer’s sound and graphics card. 
- There are network services that allow transparent access to a computer’s resources like SSH.
- Client/ server networking allows a system to connect to a server which offers various services to its clients.
- Numbered access points or ports are used for providing these services beyond the network address of the server. 
- Maximum one running program can be associated to each of the port number which will handle all the requests.
- A user program can then access the local hardware resources by making a request to the kernel of its operating system.

11. Security: 
- The security of a computer system depends on the proper working of the technologies involved in it. 
- A modern OS lets you access many resources both for the internal applications and external devices through the kernel. 
- The operating system must have the capability of deciding which requests are to be allowed and which are to be rejected. 
- There are some systems which decide this on the basis of some requester identity which they further classify as privileged or non–privileged. 
- For establishing the identity there has to be some form of authentication. 
Mostly a username or ID is quoted along with a password. 
- Some other methods are bio-metric data or magnetic cards. 
- There are cases where no authentication is required for accessing resources. 
Another concept under security is the authorization. 
- The services which can be accessed by the requester are tied to his/ her account or to group in which he/ she belongs. 
- Some auditing options are also offered by systems having a high security level. 
- With these the requests from various sources can be tracked. 
- Internal security is also essential from the programs that are currently executing. 
- It is maintained by raising interrupts to the kernel of the OS. 
- If direct access is provided to the programs for hardware, then security cannot be maintained.

12. User Interface: 
- For an operating system to be operated by a user, a user interface is required. 
- This interface is termed as the shell and is vital if the operating system is to work according to the user’s instructions. 
- The directory structure is observed by the user interface and then it sends requests for the services wanted by the OS from the input hardware devices. 
- It also sends requests to the operating system demanding for the status messages and prompts to be displayed on output hardware devices. 
- There are two most common forms of the user interface namely the GUI (graphical user interface) and the CLI (command line interface). 
In the former, the environment is visual and in the latter case the commands have to be typed line by line. 
- Almost, all the modern operating systems come with a graphical user interface.
- In some operating systems such as Mac OS, the GUI is already integrated in to its kernel. 
- There are some operating systems that are modular in nature.  

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