General Overview Of UNIX System

First UNIX system was developed in 1969 and ran on systems from microprocessors to mainframes and provided a common execution environment across them. The system was divided into two parts : Programs and services: It is the part readily apparent to users e.g. shell, mail text editor etc. Operating System: That supports above-mentioned programs and service. The early version of UNIX […]

Kernel Architecture of Various Popular Operating Systems.

Overview : UNIX : Layered Architecture Linux : Monolithic Architecture Windows : Hybrid Architecture (Microkernel + Layered) Mach : Microkernel Architecture. UNIX KERNEL ARCHITECTURE : Unix OS considers files and processes as the most important entities.   Unix offers a shell that acts as a command interpreter between the user and the kernel. The relevant part of the kernel is […]

Virtual Machine Architecture

Virtualization can be defined as the process of creating multiple copies of an object. A virtual machine is a virtualization of a machine. The software that creates multiple copies of a machine is called a virtual machine monitor (VMM) or a hypervisor. Each virtual machine have its own OS called ‘guest OS’ and the OS on which hypervisor is running […]

Types of Operating System Architecture Models

There are mainly three types of operating system architecture models : Monolithic OS : Used in older but smaller operating systems. Operating system is divided into procedures. Each procedure have a particular task and all procedures have common data structures and system tables. Each procedure can call other procedures. Resulting in high degree of inter-process dependency. Very little importance is […]

Processor Execution Modes

There are mainly three types of OS architecture models : Monolithic OS Layered OS Client-server or microkernel OS In every model, there are two modes of processor execution : the user mode and the system mode. Application programs run in the user mode whereas the operating system runs in the system mode. The system mode is also called the kernel […]

Design Goals of Operating Systems.

The design goals of operating systems are : POSIX Compliance : POSIX (Portable operating system interface bases on Unix) is an IEEE standard 1003.1-1988. This standard helps in bringing comptibility among the various OSes. Extensibility : It is the ability of an OS to grow and change over time, according to the changing requirements of the user and the market. […]

Types of Operating Systems.

Various types of operating systems are : Single User OS : There is only one user and only his/her programs in the system memory. So there are not security issues too. This type of OS is called a ‘single user mono programming‘. e.g. DOS (Disk operating system) Multi-User OS : System is one but it is connected with multiple terminals […]

How operating system boots (booting process)?

Every time a computer is turned on a monitor program is loaded from the secondary memory into main memory, which takes control of the computer and provides an interface to interact. Steps involved in booting process of a general OS : Basic Input Output System (BIOS) is stored in ROM, which capable of doing I/O operations on I/O devices. When […]

What are Objectives of an operating system?

The objectives of an operating system are : Providing the ‘user-friendly’ interface so that the user need not bother about the underlying hard-ware. The commands given by user in an natural language are interpreted by the operating system, which in turn uses the hardware to get the required task done. Creating an environment for other programs to be executed on […]

What is an Operating System?

When the system is switch on, the operating system is automatically loaded into the main memory and it takes control of the computer system. The operating system provides an interface to the user for interaction with the machine by way of managing files, executing a program, or printing an output etc. The software running on a system can be divided […]