Download Unit 1

Operating Systems
Operating Systems
Unit 1:
– OS objectives
– Mode of operation
– Components
– Architecture
– Linux
– Windows XP
What Is an Operating
System?
• Computer = set of able resources
– processor(s), memory, I/O & communication devices
• OS
– enables use of resources
– manages resources
• resources not limited to hardware
• shift from:
– pure efficient use of resources
– enhance user experience
COP 4994 - Operating Systems
to
2
Mode of operation
• Kernel:
– substance, core, center, essence, gist, heart,
heart and soul, inwardness, marrow, meat,
nub, pith, sum, nitty-gritty
• pieces of software that perform OS tasks
• has privileged access to resources
COP 4994 - Operating Systems
3
Terminology
• kernel mode or kernel space
• user mode or user space
• system call:
– user mode program invokes kernel mode
functionality
COP 4994 - Operating Systems
4
Operating System
Components
•
•
•
•
•
Processor scheduler
Memory manager
I/O manager
Interprocess communication manager
File system manager
COP 4994 - Operating Systems
5
Operating System
Architectures
• Operating systems tend to be complex
– Provide many services
– Support variety of hardware and software
– Operating system architectures help
manage this complexity
• Organize operating system components
• Specify privilege with which each component
executes
COP 4994 - Operating Systems
6
Operating System
Architectures
•
•
•
•
monolithic
layered
micro-kernel
distributed
COP 4994 - Operating Systems
7
Monolithic Architecture
• Monolithic operating system
– Every component contained in kernel
• direct communication among all elements
• highly efficient
– Problems:
• complexity
• new devices, emerging technologies
– enabling, protection
COP 4994 - Operating Systems
8
Monolithic Architecture
COP 4994 - Operating Systems
9
Layered Architecture
•
•
•
Groups components that perform
similar functions into layers
Each layer communicates only with
adjacent layer
System calls might pass through many
layers before completion
COP 4994 - Operating Systems
10
Layered Architecture
COP 4994 - Operating Systems
11
Microkernel Architecture
• Microkernel
– provides only small number of services
– attempt to keep kernel small and scalable
• High degree of modularity
• Extensible, portable and scalable
• Increased level of inter-module
communication
COP 4994 - Operating Systems
12
Microkernel Architecture
COP 4994 - Operating Systems
13
Distributed Operating
Systems
• Network operating system
– Runs on one computer but allows its
processes to access remote resources
• Distributed operating system
– Single OS manages resources on more than
one computer
COP 4994 - Operating Systems
14
Distributed Operating
Systems
COP 4994 - Operating Systems
15
Linux Kernel Architecture
• Monolithic kernel:
Contains modular components
– Process management
– Interprocess communication
– Memory management
– File system management
• VFS: provides a single file system interface
– I/O management
– Networking
COP 4994 - Operating Systems
16
Linux Kernel Architecture
COP 4994 - Operating Systems
17
Loadable Kernel Modules
• Enables code to be loaded on demand
• Reduces the kernel’s memory footprint
– Kmod: a kernel subsystem that manages
modules without user intervention
• Determines module dependencies and loads and
unloads them on demand
– Problem: kernel and module versions
COP 4994 - Operating Systems
18
Windows XP Kernel
Architecture
• Modified microkernel
– has layers
– has modular components within layer
– Microkernel
• Basic system mechanisms
• Thread scheduling, interrupt dispatching, etc.
• Abstracts hardware specifics that differ between
architectures
COP 4994 - Operating Systems
19
Windows XP Kernel Architecture
COP 4994 - Operating Systems
20
Windows XP Kernel
Architecture
• Executive
– main operating system subsystems
• Environment subsystems
– Provide a specific computing environment
for user-mode processes:
– Examples: Win32, SFU, WOW64
COP 4994 - Operating Systems
21
Agenda for next week:
• Chapter 3: Process Concepts
• Chapter 4: Thread Concepts
• Read ahead !
COP 4994 - Operating Systems
22