Welcome to the new tutorial on Unix, a beginner's guide to Unix. Let us learn/understand the essentials and basic concepts of the Unix Operating System with hands-on examples.

In this introductory Unix module will learn:

• What is the Operating System
• Unix Operating System
• Features of Unix
• Unix System Architecture
• Different variations/flavors of Unix
• Unix File System
• Unix Commands

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Hi All, I'm Dinanath Jayaswal, Senior UI/Web Developer and Adobe Certified Expert Professional, I wanna welcome you to the Introduction to Unix Operating System/Unix tutorial for Beginners.

This Course/Tutorial is ideal for:

• Freshers
• Intermediates
• Beginner Programmers
• Any Developer/Designer

By the end of this series, you will be able to understand:

• What is the Operating System
• Unix basics and advanced concepts
• Unix Architecture
• Unix Command usage

• Computer Basics

1. Introduction to Operating System
   • 1.1. What is OS (Operating System)
   • 1.2. Functions of Operating System
   • 1.3. Popular Operating System
2. Introduction to Unix
   • 2.1. History of Unix Operating System
   • 2.2. Features of Unix
   • 2.3. Compare different Operating System (MS-DOS, MS-Windows, Unix)
   • 2.4. Difference between different Operating System (Unix, MS-DOS, MS-Windows)
3. Unix Architecture
   • 3.1. Different flavors/variations/varieties/versions of Unix
   • 3.2. Unix System Architecture-Structure
     • 3.2.1. Kernel
     • 3.2.2. Shell
     • 3.2.3. Programs

In this section, you will be able to understand the fundamentals of Operating Systems, its functions and various Operating Systems used in the world.

• OS (Operating System) is a set of programs/package acts as an intermediary/interface between computer software, end-user and computer hardware
• An operating system (OS) is a collection of system software that manages computer hardware, software resources, and provides common services for computer programs
• Programs which helps to manage/communicate between software and hardware (low-level software manages hardware by controlling the execution of programs)
• Core/brain/heart of machine's/device's software and provide an environment to execute programs
• OS (Operating System) controls the allocation of resources and services such as (Memory, Processor, Devices, Information, controlling attached devices/peripherals)

Here is the list of important functions performed by an Operating System:

• Co-ordination between Software and Hardware
• Memory Management
• Device Management
• Processor Management
• Security
• Error detection
• Co-ordination between User and Software
• Control over system performance
• Task/Internal Job scheduling
• File Management

Here are some popular and widely used Operating Systems (OS) - Some popular Operating Systems include:

• Unix
• DOS
• Microsoft Windows
• macOS (Apple mac)
• Linux (Unix clone)
• Android (Mobile OS)
• iOS (Apple Mobile OS - iPhone, iPad, iPod)

In this section, you will be able to understand the basic concepts-history of Unix operating systems, features of Unix, along with its comparison, similarities and difference between other Operating Systems in the market like MS-DOS and MS-Windows.

• Unix is developed by Ken Thompson and Dennis Richie at AT&T Bell Laboratories Research Center, USA in the year 1969
• Unix is multi-user, multi-tasking, and multi-processing, high-function, interactive Operating System
• Unix is terminal ie. command prompt based Command Line Interface/Interpreter (CLI), UNIX system also have a Graphical User Interface (GUI) similar to Microsoft Windows which provides an easy to use environment
• Initially, Unix was written in Assembly language, First Operating System is written in HLL ie. High-Level Language (C)
• Originally Unix is spelled as UNICS (Uniplexed Information Computing System/Service)
• Later Unix is re-written in C language and renamed as Unix
• Some of Unix OS ie. distributions are Free (Open Source - Linux) and some are not free (license needed)

Mentioned below the features and capabilities supported by Unix Operating System:

• Multi-user capability
• Multi-tasking
• Multi-process
• Hierarchical File Structure / Hierarchical File System
• Open Source System
• Portability
• Programming Utility/Facility
• Communication Facility
• Security
• Tools and Utilities
• Piping (Pipes & Filters)
• Help Facility - Integrated Help
• Modularity
• Unix Shell
  
  
• Multi-user capability
  • Multiple ie. many users can use the machine simultaneously supported via terminals/command prompt
• Multi-tasking
  • Multiple programs can be run at a time
• Multi-process/Multi-processing
  • Each user can execute multiple/many/several processes simultaneously
• Hierarchical Structure
  • Unix directories/folders system are present like a tree structure to support, organize and maintain files
• Open Source System
  • Some of Unix OS ie. distributions are Free (Open Source - Linux), users can modify source code as per needs and requirements
• Portability
  • Unix allows users to transfer data/information/files/folders from one system to another
• Programming Utility/Facility
  • Unix Shell can be used as a Programming/Scripting Language
• Communication Facility
  • Communication between different users is possible by using/sharing some information
• Security
  • Unix Operating System provides System-level security controlled by the system administrator and file-level security controlled by the owner of the file/folder
• Tools and Utilities
  • Supports/provide many useful tools/software/utilities used for software development
• Piping
  • The output of the current command can be used as an input of next command/process (last-current-next process/command can be linked/chained)
• Help Facility - Integrated Help
  • Unix man command is used to get/view any command help
• Modularity
  • Unix Operating System consists of multiple independent modules/programs/utilities which perform a specific task
• Unix Shell
  • Unix Shell a command interpreter that helps to interact with Unix OS ie the Kernel. (Shell takes input/command from a user and executes programs-run command)

Similarity between Unix and MS-DOS:

• Command Line Interface CLI / Command Terminal Window / Command Prompt
• I/O (Input Output) redirection concepts
• Hierarchical directory structure (Root directory at the top)
• Read-Write (RW) and execute permissions on files/folder
• Wildcard Character support

Similarity between Unix and MS-Windows:

• Graphical User Interface (GUI)
• Multi-tasking Operating System
• Built-in networking with TCP/IP as the standard protocol

Difference between Unix and MS-DOS:

Difference between Unix and MS-Windows:

In this section, will get more information on different Unix flavors/variations/variety/version, Unix Architecture with Kernel and Shell.

There are many ie. different flavors/variations/variety/versions of UNIX available in the market, although they share common similarities. The most popular varieties of UNIX are Sun Solaris, GNU/Linux, and macOS X:

An operating system is a collection of software, each designed for a specific function. Here is a basic block diagram of a Unix system Architecture-Structure:

Hardware (Physical Devices)

• The Hardware layer of the Unix Operating System controls the use of physical system resources, such as memory manager, process manager, disk drivers, devices, and so on
• The hardware consists of all input and output peripheral devices (RAM, HDD, CPU and so on)

The UNIX operating system is made up of three parts named as the Kernel, the Shell and the Programs:

1. Kernel
2. Shell
3. Programs

1. Kernel

• The kernel is the hub/heart/core of Unix Operating System

2. Shell

• Shell is an interface between a User/User application and Kernel

3. Programs / User-Application Program

• Utility programs and applications are given by the user are handled in this layer

• The kernel is the hub/heart/core of Unix Operating System
• It acts as an interface between the Hardware and Shell layer
• It allocates the time and memory to the programs and handles the communications in response to the system calls
• Most of the tasks such as memory management, task scheduling, file management, and so on are performed by Kernel
• It manages external commands in Unix
• Manages system resources, and enforce the security scheme
• Manages the machine's memory and allocates it to each active/currently running process
• Manages processor interrupts, and takes care of error handling
• Schedules the work is done by the Central Processing Unit CPU and controls how processes are executed
• Manages the creation and terminations of processes, and the communication between processes
• Allocates and manages resources used by each user
• Allows user processes, including shell commands to run Kernel instructions

• Shell is an interface between a User/User application and Kernel
• Shell is the command interpreter in Unix, it supports a Command Line Interface, and also allows scripting
• It serves as the interface between the User and the Kernel, helps to interact with Unix OS ie the Kernel (Shell takes input/command from a user and executes programs-run command)
• The Shell is a Command Line Interface (CLI), As and when we type a command at the terminal, the shell interprets the command and calls the corresponding program
• The Shell layer processes the user request
• Shell uses standard syntax for all the commands
• It provides a rich set of commands
• Shell is an environment in which we can run our commands, programs and shell scripts
• A file "/etc/shells" contains a list of all the Shells supported and available in the system

Different Shells available with most of the Unix variants/flavors: (Shell Types / Shell variants)

• Bourne shell (sh)
• C shell (csh)
• Korn shell (ksh)
• TelShell (wish)
• Bourne Again Shell (bash)

• Utility programs and applications are given by the user are handled in this layer
• The commands are themselves called as programs in Unix
• There are various commands and utilities which you can make use of in your day to day activities. cp, mv, cat and grep, etc.
• Data in Unix are organized into files and files are organized into directories which are further organized into a tree-like structure called as the file system