Computer - Operating System

It is a program with following features:

• An operating system is a program that acts as an interface between the software and the computer hardware.
• It is an integrated set of specialised programs that are used to manage overall resources and operations of the computer.
• It is specialised software that controls and monitors the execution of all other programs that reside in the computer, including application programs and other system software.

Objectives of Operating System

• To make a computer system convenient to use in an efficient manner
• To hide the details of the hardware resources from the users
• To provide users a convenient interface to use the computer system
• To act as an intermediary between the hardware and its users and making it easier for the users to access and use other resources
• To manage the resources of a computer system
• To keep track of who is using which resource, granting resource requests, according for resource using and mediating conflicting requests from different programs and users
• To provide efficient and fair sharing of resources among users and programs

Characteristics of Operating System

• Memory Management -- keeps tracks of primary memory i.e. what part of it is in use by whom, what part is not in use etc. and allocates the memory when a process or program requests it.
  
• Processor Management -- allocates the processor(CPU) to a process and deallocates processor when it is no longer required.
  
• Device Management -- keeps track of all devices. This is also called I/O controller that decides which process gets the device, when, and for how much time.
  
• File Management -- allocates and de-allocates the resources and decides who gets the resources.
  
• Security -- prevents unauthorized access to programs and data by means of passwords and similar other techniques.
  
• Job accounting -- keeps track of time and resources used by various jobs and/or users.
• Control over system performance -- records delays between request for a service and from the system.
  
• Interaction with the operators -- The interaction may take place via the console of the computer in the form of instructions. Operating System acknowledges the same, does the corresponding action and informs the operation by a display screen.
  
• Error-detecting aids -- Production of dumps, traces, error messages and other debugging and error-detecting methods.
  
• Coordination between other software and users -- Coordination and assignment of compilers, interpreters, assemblers and other software to the various users of the computer systems.
  
  

  Computer - Internet and Intranet

  Internet

  It is a worldwide system which has the following characteristics:
  
  
• Internet is a world-wide / global system of interconnected computer networks.
• Internet uses the standard Internet Protocol (TCP/IP)
• Every computer in internet is identified by a unique IP address.
• IP Address is a unique set of numbers (such as 110.22.33.114) which identifies a computer’s location.
• A special computer DNS (Domain Name Server) is used to give name to the IP Address so that user can locate a computer by a name.
• For example, a DNS server will resolve a name http://www.tutorialspoint.com to a particular IP address to uniquely identify the computer on which this website is hosted.
• Internet is accessible to every user all over the world.

Intranet

• Intranet is system in which multiple PCs are connected to each other.
• PCs in intranet are not available to the world outside the intranet.
• Usually each company or organization has their own Intranet network and members/employees of that company can access the computers in their intranet.
• Each computer in Intranet is also identified by an IP Address which is unique among the computers in that Intranet.

Similarities in Internet and Intranet

• Intranet uses the internet protocols such as TCP/IP and FTP.
• Intranet sites are accessible via web browser in similar way as websites in internet. But only members of Intranet network can access intranet hosted sites.
• In Intranet, own instant messengers can be used as similar to yahoo messenger/ gtalk over the internet.

Differences in Internet and Intranet

• Internet is general to PCs all over the world whereas Intranet is specific to few PCs.
• Internet has wider access and provides a better access to websites to large population whereas Intranet is restricted.
• Internet is not as safe as Intranet as Intranet can be safely privatized as per the need.

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