Architecture of UNIX Operating System


UNIX is the Operating System and Operating System is the Program used for interaction of user (uses computer for his/her work) and hardware (physical parts of the computer system).

In UNIX OS Architecture there are set of layers as often does in all operating system architecture: -

  • Application Program Layer.
  •  Shell, Editors & Commands Layer.
  •  Kernel Layer.
  •  Physical (Hardware) Layer.

Architecture of Unix Operating System
Architecture of UNIX Operating System

Any type of program in UNIX  OS process through kernel layer. Kernel Layer means the  center or we can say origin of  UNIX OS. So, we can interact any type of program  in UNIX OS with Kernel through: -
  1. Shell (sh) and Editors (Vi) System Calls.
  2. Commands
  3. Or, through the programs created separately but, presents in (Shell, Editors & Commands Layer), Such as: - “a.out” named programs , where “a.out” is the extension of  files produced by C Compiler.
Kernel Layer is the main layer in UNIX OS Architecture . So, the everything below the System Call interface and above the physical hardware is Kernel.
The Kernel provides : -
  • File System
  • CPU Scheduling
  • Memory Management
  • And, other operating System functions through System Calls.   
There is the term used System Calls , you think so, what is the term System Calls ? These the instruction given by Shell(sh), Editors(vi) & Commands. These instructions are given to Kernel, so it will do various operations for the program called by statements and  Kernel can exchange data between the program 
and  itself.

System Calls in UNIX OS are grouped into three categories: -
1) File Manipulation
2) Process Control
3) Information Manipulation

There is another category also that is, Device Controller, but this category is not included in main categories because, this category is for devices and in UNIX devices are treated as (special ) files. So, the system calls of devices supports both files and device manipulation.

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