basics

1) Kernal
2) Shell
3) Utilites

Kernal-

(i) take care of your Operating system
(ii) its a memory resident program(available in memory all the time)
(iii) loaded at boot time
(iv)manages entire resources of your system.these resources available to each user as a unit
(v) also provide service to user application, i.e. voice manager , Process ,Schedular


Functions of kernal:

(i) schedules work done by cpu(work of user is carried out as early as possible).as FCFS (first come first serve)
(ii) Transfer data from one part of machine to another
(iii) Interpret and execute instructions from shell
(iv)Enforce file access permissions

SHELL:

(i) Command line interpretor
(ii ) the moment you logged in you got placed in a shell program

shell prompt ----> $

(iii) shell moves your request to kernal
(iv) shell checks list of valid commands
(v) donot put burden on kernal
(vi) shell takes command from user and pass on to OS kernal to execute it

Types of Shells:

(i) Bsh -> Bourne shell
(ii) Bash -> Bourne Again Shell
(iii)Tcsh -> turbo c shell
(iv) Csh -> C shell
(v) Ksh -> Korn shell