Operating system structure

Operating system structure

1. Operating System Structure

2. Simple Structure System started as small , simple and limited systems and then grew beyond the scope. MS DOS Interfaces and layers are not well separated Limited by hardware Base hardware made accessible Unix OS Limited by hardware functionality Two separate parts kernel and system programs Kernel separated into series of interfaces and device drivers. Added and expanded

3. Simple Structure

4. Simple Structure

5. Layered approach Proper hardware support ,OS divided into pieces Better control on computer and applications Implementers have freedom to change inner working of OS Modular system OS broken into number of layers Lower layer invoke by higher layers. (DS and Routines) Adv : Simplicity of construction and debugging Each layer implement with operations of lower layer Hide existence of lower level layer from higher layers

6. Layered approach Disadvantage: tends to be less efficient than other types Each layer adds overhead of system call

7. Microkernel System Structure Moves as much from the kernel into “ user ” space. Communication takes place between client program and various services in user program by message passing. Benefits: easier to extend a operating system easier to port the operating system to new architectures more reliable (less code is running in kernel mode) more secure

8. Modules structure Object oriented approach Create modular kernel Set of core components and other services are linked during boot time and l oad time Loadable module Solaris system : organized around core kernel with seven types of lodable modules

9. Modules structure Scheduling classes File system Loadable system calls Executable formats Streams modules Miscellaneous Device and bus drivers