3.how unix is organized

The UNIX system is functionally organaized at three levels ::

• The kernal ,which schedules tasks and manages storage
• The Shell, which connects and interprets users commands ,call programes from memory and executes them : and
  
• The tools and applications that offer additional functionality to the operating system

the three levels of unix system ::

• Kernl
• Shell
• Tools & Applications

The Kernel :: The heart of the operating system ,the kernel controls the hardware and turns part of the system on and off at the programmers command .if we ask the computer to list (ls) all the files in a directory,the kernel tells the computerto read all the files from the disk and display them on the screen.



The Shell :: There are several types of shells ,most notably the command driven Bourne Shell ($sh) and the C shell ($csh)and menu-driven shells that make it easier for beginners to use.
What ever shell iis used ,its purpose is same -- to act as an interpreter between the user and the computer.

Tools & Applications :: There are hundreds of tools available to UNIX users,although some have been written bythird party vendors for specific applications.Typically,tools are grouped into categories for certain functions,such as word processing,business applications,or programming.
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