CS代考程序代写 assembler gui Java distributed system file system FTP compiler interpreter flex CSI3131 Module 1

CSI3131 Module 1
–
Overview
Introduction / of OS
1
▪ Do a quick overview of the organization of
▪ Introduce the operating system to understand its role and main functions
Reading: Chapter
and
2
(Silberchatz)
Goal:
–
computers
input / output, architecture and general operations.
processor (CPU), memory, and
1

Organization
Computer system
Operating system
2

Memory
Device Controllers
CPU
Hardware
Organization
Computer system
Operating system
Bus
3

Main hardware
▪ Processor (CPU)
▪ Main memory (real memory, RAM)
▪ Contains code and data
▪ I / O Modules (I / O Controllers, I / O Processors …)
▪ hardware (with registers: I / O ports) for data transport between CPUs and peripherals such as:
• secondary memory (e.g. hard disks)
• keyboard, screen …
• Communication equipment
▪ Interconnection (ie: Bus)
▪ for communication between processor (s), memory and I / O modules
4

Memory
Device Controllers
CPU
Hardware
Memory Structure
Organization
Computer system
Operating system
Bus
Secondary Memory Main Memory
5

Memory structure
▪ Main memory
▪ Accessible directly by the CPU
▪ A program must be in main memory to be executed by the CPU
▪ Main memory is not large enough to hold all programs and data
▪ The main memory is volatile – its content changes on loss of power or on restart.
▪ Secondary memory
▪ Contains large amounts of data / files, permanently.
▪ In general, a hierarchy exists for memory devices which varies according to speed, cost, size and volatility.
6

Hierarchy of memory devices
7

Hierarchical organization of memory
8

Memory
Device Controllers
Bus CPU
I/O
Structure
By interruption
DMA
Hardware
Memory Structure
Organization
Computer system
Operating system
Direct I/O
Secondary
Memory Main
Memory
9

Structure of the I / O controller
▪ Bus data are buffered in the “data register” (I / O ports)
▪ The “Status / Control” register contains:
▪ information on the status of the I/O operation ▪ the control information coming from the CPU
▪ The “I/O logic” circuit interacts with the CPU via the bus. ▪ Contains logic specific to the interface of each device
10

Communication techniques for I/O
▪ 3 techniques are possible: ▪ Scheduled I/O
• Does not use interrupts. CPU must wait after each I/O operation
▪ I/O triggered by interrupts
• The CPU can execute code during the I/O operation: it is interrupted when the operation is complete.
▪ Direct memory access (DMA)
• A block of data is transferred directly to / from memory without going through the CPU
11

I/ O
Interrupt
12

Modern computer operation
13

Memory
Multi processor
Clusters
Device Controllers
Bus
CPU
By
Direct interruption I/O
Secondary DMA Memory
Main Memory
One * processor
Hardware
I/O
Structure Architecture Memory
Structure
Organization
Computer system
Operating system
14

Computer systems architecture
▪ Systems with a single processor
▪ From PDA to central computer
▪ Almost all have specialized processors for graphics, I/O
• This is not considered to be multi-processor ▪ Multiprocessor systems
▪ Increased processing throughput ▪ Economies of scale
▪ Increased reliability
▪ Asymmetric multiprocessing
• Each processor is given a specific task
▪ Symmetric multiprocessing (most common) • All processors perform all OS tasks
▪ Clusters, distributed systems 15

Memory
Multi processor
Clusters
Device Controllers
Bus CPU
Structure Architecture Memory
interrupt Secondary DMA
Memory Main
One * processor
Hardware
I/O
Direct I/O
Structure
Organization
Computer System
Operating System
Memory
Services What is it?
User View
User Interfac GUI or CLI
16

Abstract view of the components of a computer system
17

Outlook for the
▪ This is my system, only I use it
▪ ie PC of which a user monopolizes
▪ OS maximizes user work (or play)
▪ OS designed for ease of use, not resource use. ▪ Portable systems – low hardware demand
▪ This is the big dedicated computer, I’m lucky to have CPU time
▪ ie the central computer or the minicomputer
▪ The OS is designed to maximize the use of resources (CPU, memory, I / O)
▪ Computer sharing
▪ ie workstations connected to a network of servers
▪ Dedicated and shared resources
▪ OS balances individual needs with resource utilization needs
▪ What? There is a computer inside.
▪ Embedded systems designed to run with minimal intervention
computer user
18

do operating
systems
do?
What
▪ Write a sentence or two that summarizes the role of the OS.
▪ OS is the program most involved with hardware • Material abstraction
▪ The OS allocates resources
• Manage all resources
• Deal with conflicting demands for efficient and fair use of resources
▪ OS is a control program
• Controls the execution of programs (ie processes) to avoid errors and misuse of the computer.
19

The definition of the operating system
▪ So what is the operating system?
▪ No universal definition accepted
▪ “Everything the supplier delivers when ordering an OS” is a first approximation
▪ But this varies a lot.
▪ “The program that runs all the time” is the one
used in this course
▪ This is the (Kernel)
▪ Any other program is a system program (delivered
with the OS) or an application program.
▪ What does “run all the time” mean? When I play Tetris, Tetris is executed by CPU – right?
20

System programs
▪ Are they part of the operating system
▪ Anything not in the kernel, but shipped with
the OS
▪ All depends on the OS and the supplier
▪ Can provide multiple system services, ie UNIX commands (CLI) are system programs for performing system tasks.
▪ Much of the user’s perspective on OS is defined by system programs, not directly by system calls to the kernel.
21

Systems program
▪ System programs (also called utility programs) provide an environment for program development and execution. Services:
▪ File management – ie copy, rm, ls, mkdir
▪ Status information – ie ps, who, regedit
▪ Editing files – editors
▪ Programming language service – ie cc, javac
▪ Loading and running programs – loaders, debuggers
▪ Communications – ssh, ftp
▪ Application programs – browsers, electronic pages, games
22

Services offered to user programs
▪ Input / Output operations
▪ Hardware access is through the kernel for the running
program
▪ Communications
▪ Communication between programs of the same
computer or with those of other computers
▪ Can be done with shared memory or messages
▪ Dealing with errors
▪ Detection
• Hardware errors (internal or external): memory, failure of an I / O device
• Software errors: overflows, prohibition of access to a memory slot
• Inability for OS to satisfy request
▪ Reaction: just report the error to the application, try the operation again, suspend the application
23

Services to ensure efficiency and proper functioning
▪ Resource allocation and management
▪ Required to serve multiple users and multiple
programs
▪ Some resources have their specific management code:
• CPU, main memory, file system
▪ Others are managed via a general code – I / O
▪ Accounting
▪ Statistics on the use of resources by users
▪ Protection and security
▪ Prevent intruders (unauthorized users) from accessing
the system
▪ Prevent users from accessing resources that are not intended for them
24

User interface
Command Line Interface (CLI) allows command entry directly from the keyboard
▪ The command interpreter is a program that reads commands typed by the user
• Often referred to as the “shell” (UNIX terminology) ▪ The execution of a command is done one of two
ways
• The interpreter executes the command
• Programming instructions allow the interpreter to execute
“shell” programs
• The command is used to start a separate program (eg a system program)
–
CLI
25

–
GUI
User interface
▪ User-friendly interface that represents a desktop surface ▪ With mouse, keyboard, and monitor
▪ Icons represent files, programs, actions, etc.
▪ Invented at Xerox PARC
▪ Many systems include CLI and GUI interfaces.
▪ Microsoft Windows is GUI with a CLI “command” shell
▪ Apple Mac OS X contains the “Aqua” GUI interface and a UNIX kernel and therefore the “shell”
▪ Solaris and Linux are CLI with optional GUI interfaces (Java Desktop, KDE)
▪ Which interface do you prefer?
26

OS interfaces
▪ CLI and GUI – interfaces for the user
▪ What are the other interfaces of the operating
system?
▪ Interface for programs that run on the computer and request services from the OS
• The system call interface
▪ Hardware interface
• Interrupts, drivers device controllers
27

Memory
Multi processor
Clusters
I/O Management
Device Controllers
Bus CPU
Structure Architecture Memory
interrupt Secondary DMA
Memory Main
One * processor
Hardware
I/O
Direct I/O
Structure
Organization
Computer System
Memory
Services What is it?
User Interfac GUI or CLI
Operating Management System
Operation
Dual Mode
Process
Memory Management
User View
28

Operating system operations
▪ The OS works on the basis of interrupts
▪ Interrupts come from hardware AND software
▪ Mouse click, divide by zero, OS service request
▪ Timer interruption (process time finished), memory access error (process wants to modify another one or the OS).
▪ Some operations will have to be done only by a reliable program.
▪ Access hardware, memory management registers.
▪ An evil user program could damage other
processes, steal the system, …
▪ Solution: operation in dual mode.
29

User mode and kernel mode
▪ Dual mode operation allows the OS to protect itself and other components
▪ User mode and kernel mode (or supervision)
▪ Bit mode is found in the hardware
• Distinguish the mode (user or kernel)
• Some instructions are privileged
• Call to OS changes the mode to kernel and the return of the call changes it to user mode.
30

Transition from user mode to kernel mode
▪ A timer prevents processes from taking over the system
▪ An interruption after a period of time
▪ OS decrements a counter
▪ When the counter is zero, change process or end process.
▪ Configure before giving control to the process to regain control or terminate the program.
31

The system call
▪ The interface that offers OS services to programs
▪ Process control:
• to run a program.
▪ File management:
• create / open / read / write a file, list a directory.
▪ Device management:
• request / release of a device
▪ Information management:
• time management, process attributes and files
▪ Communication:
• open / close a connection, send / receive messages
32

System call (continued)
▪ Normally written with high level programming language (eg C).
▪ Implemented with software interrupt
▪ The software interrupt changes the mode bit to kernel mode and calls the appropriate subroutine according to an array of system calls and the interrupt number
• Linux example: http://docs.cs.up.ac.za/programming/asm/derick_tut/syscalls
.html
▪ At the end of the subroutine, the mode returns to user mode and values are returned to the calling program.
33

System call API
34

How to access system calls
▪ Often accessed through programs with an application programming interface (API) and not directly system call
▪ Common APIs:
▪ Win32 for Windows
▪ POSIX API for POSIX systems
• UNIX, Linux and MAC OS X
▪ Java API for Java Virtual Machine (JVM)
▪ The calling program does not know anything about the
implementation of the system call.
▪ Simply obeys API standards: parameters to provide, return values, and desired operation
▪ The OS interface details are hidden behind the API.
• Managed by the API library (set of functions supplied with the
compiler)
▪ Possible to use system calls directly 35

Example of the standard API in C
▪ The printf () function which makes a write() system call
36

Main
▪ Process management
▪ A process with a thread has a single program counter
▪ The OS manages the resources required by the processes
• CPU, memory, I/O, files
• Initialization data
▪ The OS manages the activities of the processes: creation and destruction, interactions between processes, etc.
▪ Memory management
▪ Memory management determines which process and when it occupies memory to optimize CPU usage and the computer’s response to users
▪ Secondary memory management
▪ The OS gives a uniform and logical view of the information stored
in secondary memory
▪ File system, mass storage
▪ The I/O subsystem
▪ A role of the OS is to hide the various peculiarities of the user’s
devices
operations
of the operating system
(OS)
37

realization
of OS
Design and
▪ The design of the SE is mainly affected by the choice of material and type of system
▪ Batch, time-shared, one-user, multi-user, distributed, real-time, general use
▪ User needs versus system needs
▪ User needs – easy to use, easy to learn, reliable, and fast
▪ System requirements – easy to design, simple to build and maintain, as well as flexible, reliable, error-free, and efficient.
▪ Implementation
▪ Traditionally in assembler
▪ Today, especially in C, with small sections in assembler (drivers, manipulation of registers)
39

System structure
▪ Internal structure of OS vary
▪ Since needs/requirements vary
▪ Simple hardware, simple functions ▪ Simple monolithic structure
▪ More resources and complex functions
▪ Layered Structure
▪ MS-DOS and traditional UNIX are monolithic OS which use a layered structure.
▪ Even more resources and functions, with a focus on flexible and elegant design
▪ Micro-Kernel structure (MACH, QNX, Windows NT)
▪ Flexibility and efficiency
▪ Modular structure (Solaris, Windows NT)
40

UNIX structure: few layers
41

Virtual machines: the problem and the solution
▪ How to allow different OS to run on a single physical machine?
▪ Not easy, because each OS requires direct access to the hardware
▪ SOLUTION: A program that creates a layer that makes several physical machines available virtual
▪ On each we can run a different SE 42

System model
(a) A single real machine and single kernel
(b)
Several
virtual
machines and
several
kernels
43

Operation
▪ The VM system allows unprivileged instructions to execute normally
▪ System calls are executed by the VM system and the results are passed to the virtual machine on which the process is running
44

Advantages
▪ Each virtual machine can use a different OS! ▪ In theory, we can build virtual machines on
virtual machines!
▪ Complete protection, because virtual machines are completely isolated from each other
▪ A new OS can be developed on a virtual machine without disturbing others
45

Implementations
▪ The concept of VM is widely used to allow running one OS on another
▪ Eg. SUN, Apple, Linux allow Windows to run on their platform,
▪ They must provide Windows with an environment that Windows recognizes as its usual Intel environment.
46

VMWARE on Linux
47

Java Virtual Machine
48

We do not cover these concepts
▪ Distributed system
▪ Embedded real-time systems ▪ Multimedia systems
▪ Hand held Computers
▪ Peer to peer
▪ WEB operating system
49
Fall 2008

Thank You!
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