Explain layered architecture of unix operating system?

Answer 1

)With a neat diagram explain different layer of Unix OS? Also explain interaction between Shell an kernel using any suitable commands.

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Architecture of Unix.

Ans- The part of UNIX that manages the hardware and the executing processes is called the kernel. The kernel is a collection of programs written in C which directly communicate with the hardware. Each hardware device is viewed as a file and is called a device file. This allows the same simple method of reading and writing files to be used to access each hardware device. The file system manages read and write access to user data and to devices, such as printers, attached to the

system. It implements security controls to protect the safety and privacy of information. In executing processes the kernel allocates resources, including use of the CPU and mediates accesses to the hardware.

The user commands are translated into action by the shell which acts as an interpreter. The shell forms the outer part of the operating system and forms the interface between the user and the kernel. For each user logged in, there is shell in action. When a command is given by the user, it is examined by the shell and communicated to the kernel for execution. The functions used to communicate with the kernel are called system calls and are built into the kernel. The system calls are in all the flavors of UNIX are the same. Hence, software developed on one UNIX system can be easily run on another UNIX system.

UNIX's layered design insulates the application from the different types of hardware. This allows the software developer to support the single application on multiple hardware types with minimal effort. The application writer has lower development costs and a larger potential customer base. Users not only have more applications available, but can rely on being able to use the same applications on different computer hardware.