Architecture of Unix

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Unix Architecture

Unix Architecture

The architecture of Unix operating system is divided by into four layers. These are the hardware, kernel, system call interface(shell), and application programs/ libraries. The above Unix architecture diagram is showing all the layers.

The Kernel

The kernel is a part of the operating system. It interacts directly with the hardware of the computer through a device that is built into the kernel. The main functions of the kernel are,
  • Memory management
  • Controlling access to the computer.
  • Maintaining the file system. 
  • Handling interrupts. 
  • Handling errors. 
  • Performing input and output services.
  • Allocate the resources of the computer among users.
The kernel is the main part of the Architecture of Unix OS.

The Shell

It is a software program and it acts as a mediator between the kernel and the user. It reads the commands and then interpret them and sends a request to execute a program. So, the shell is also called a command interpreter.

It contains nearly 100 system calls. System calls tell the kernel to carry out various tasks for the program, such as
  • Opening a file.
  • Writing a file.
  • Obtaining information about a file.
  • Executing programs.
  • Terminating a process.
  • Changing the priority of processes.
  • Getting the time and date.


The hardware includes all the parts of a computer including clocks, timers, devices, parts etc. in the Unix OS Architecture.

Unix Commands and Libraries

This layer of Unix architecture includes user-written applications, using shell programming languages, and libraries of UNIX.

I hope you have cleared about the architecture of UNIX operating system notes.

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Memory Management in OS(Operating System)