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Revision no.: PPT/2K403/02 Essential Unix (and Linux) for the Oracle DBA Revision no.: PPT/2K403/02 Architecture of UNIX Systems © CMS INSTITUTE, 2004 All rights reserved No part of this material may be reproduced, stored or emailed without the prior permission of Programme Director, CMS Institute Revision no.: PPT/2K403/02 UNIX System Structure • Operating system interacts directly with Hardware • Provides common services to programs • Insulating from Hardware • Kernel is treated as an operating system • Programs are independent of the Hardware • Easy to move on different processing environment • Programs should be independent of Hardware © CMS INSTITUTE, 2004 All rights reserved No part of this material may be reproduced, stored or emailed without the prior permission of Programme Director, CMS Institute Revision no.: PPT/2K403/02 UNIX System Structure (contd.) • Programs in the upper layer communicate with Kernel using defined set of system calls • System calls instruct the Kernel to various operations • System calls also exchange the data between Kernel and program • Some Standard programs also fall in this layer i.e executable files by C compiler • Top most layer is used for other application programs eg C compiler (CC) © CMS INSTITUTE, 2004 All rights reserved No part of this material may be reproduced, stored or emailed without the prior permission of Programme Director, CMS Institute Revision no.: PPT/2K403/02 SHELL • It is a program that interprets the commands • If the command is valid then the shell directs the kernel to carry out the request • If invalid then an error message is displayed • Shell starts when an user logs in, and terminates when the user logs out • Presence of shell is indicated by a special symbol known as the shell prompt ( $ or # ) © CMS INSTITUTE, 2004 All rights reserved No part of this material may be reproduced, stored or emailed without the prior permission of Programme Director, CMS Institute Revision no.: PPT/2K403/02 The Crontab and Automation of Scripts 47 © CMS INSTITUTE, 2004 All rights reserved No part of this material may be reproduced, stored or emailed without the prior permission of Programme Director, CMS Institute Revision no.: PPT/2K403/02 48 Design & Published by: CMS Institute, Design & Development Centre, CMS House, Plot No 91, Street No.7, MIDC, Marol, Andheri (E), Mumbai –400093, Tel: 91-22-28216511, 28329198 Email: courseware.inst@cmail.cms.co.in www.cmsinstitute.co.in © CMS INSTITUTE, 2004 All rights reserved No part of this material may be reproduced, stored or emailed without the prior permission of Programme Director, CMS Institute ... Revision no.: PPT/2K 403/ 02 SHELL • It is a program that interprets the commands • If the command is valid then the shell directs the kernel to carry out the request • If invalid then an error message... set of system calls • System calls instruct the Kernel to various operations • System calls also exchange the data between Kernel and program • Some Standard programs also fall in this layer i.e... reproduced, stored or emailed without the prior permission of Programme Director, CMS Institute Revision no.: PPT/2K 403/ 02 UNIX System Structure (contd.) • Programs in the upper layer communicate with
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