SLC/Ver1.0/OS CONCEPTS/Oct'991INTRODUCTION What is an Operating System? Operating Structure -System...
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Transcript of SLC/Ver1.0/OS CONCEPTS/Oct'991INTRODUCTION What is an Operating System? Operating Structure -System...
SLC/Ver1.0/OS CONCEPTS/Oct'991
INTRODUCTIONINTRODUCTION
• What is an Operating System?
• Operating Structure-System Components-OS Services-System Calls & Programs-System Structure-Virtual Machines
SLC/Ver1.0/OS CONCEPTS/Oct'992
What is an OS?What is an OS?
• Important part of almost every computer system.
• Computer System can be divided roughly into four components-The hardware-The Operating System-The Application Program-The User
SLC/Ver1.0/OS CONCEPTS/Oct'993
What is an OS?What is an OS?
COMPUTERHARDWARE
APPLICATION PROGRAMS
COMPILER
USER1
USER2
USERN
ASSEMBLER DATABASESYSTEM
OPERATING SYSTEM
SLC/Ver1.0/OS CONCEPTS/Oct'994
What is An OS?What is An OS?
• An Operating System is similar to a government.
• We can view an Operating Systems as a resource allocator.
• An Operating System is a control program.
SLC/Ver1.0/OS CONCEPTS/Oct'995
What is an OS?What is an OS?
• No adequate definition of an OS.
• Fundamental Goal of Computer System is to execute user programs and to make solving user problems easier.
• The OS is the one program running at all times on the computer, with all else being application programs.
SLC/Ver1.0/OS CONCEPTS/Oct'996
Operating System StructureOperating System Structure
• There are several vantage points from which to view an OS-by examining the services it provides.-another by looking at the interface.-by disassembling the system into its components and their interconnections.
SLC/Ver1.0/OS CONCEPTS/Oct'997
System ComponentsSystem Components
• Process Management
• Main-Memory Management
• File Management
• I/O System Management
• Secondary-Storage Management
• Networking
SLC/Ver1.0/OS CONCEPTS/Oct'998
System ComponentsSystem Components
• Protection System
• Command-Interpreter System
SLC/Ver1.0/OS CONCEPTS/Oct'999
Process ManagementProcess Management
• A process can be thought of as a program in execution.
• A process needs certain resources.
• A process is the unit of work in the system.
SLC/Ver1.0/OS CONCEPTS/Oct'9910
Process ManagementProcess Management
• The OS responsibility in connection with process management-Creation and deletion of both user and system processes-The suspension and resumption of processes-The provision of mechanism for process synchronization, process communication.
SLC/Ver1.0/OS CONCEPTS/Oct'9911
Main-Memory ManagementMain-Memory Management
• It is a large array of words or bytes.
• Main-memory is a repository of quickly accessible data shared by CPU and I/O devices.
• The main-memory is generally the only large storage device that the CPU is able to address and access directly.
SLC/Ver1.0/OS CONCEPTS/Oct'9912
Main-Memory ManagementMain-Memory Management
• Keep several programs in memory.
• There are many different memory-management scheme.
SLC/Ver1.0/OS CONCEPTS/Oct'9913
Main-Memory ManagementMain-Memory Management
• The OS responsibility in connection with memory management-Keep track of memory.-Which processes are to be loaded.-Allocate and deallocate memory space as needed.
SLC/Ver1.0/OS CONCEPTS/Oct'9914
File ManagementFile Management
• File Management is one of the most visible components of an Operating System.
• The OS abstracts from the physical properties of its storage devices to define a logical storage unit, the file.
SLC/Ver1.0/OS CONCEPTS/Oct'9915
File ManagementFile Management
• File is a collection of related information defined by its creator.
• The OS responsibility-The creation and deletion of files.-The Support for manipulating files.-The mapping of files onto secondary storage.
SLC/Ver1.0/OS CONCEPTS/Oct'9916
I/O System ManagementI/O System Management
• One of the purpose of an OS is to hide the peculiarities of specific h/w devices from the user.
• I/O subsystem consists of-A memory management components-A general device-driver Interface-Drivers for specific hardware devices.
SLC/Ver1.0/OS CONCEPTS/Oct'9917
Secondary-Storage ManagementSecondary-Storage Management
• Main-Memory is to small and volatile.
• Computer system must provide secondary storage to back up main memory.
• Computer system uses disks as the principle on-line storage medium, for both programs and data.
SLC/Ver1.0/OS CONCEPTS/Oct'9918
Secondary-Storage ManagementSecondary-Storage Management
• The OS responsibility:-Free-space management.-Storage allocation.-Disk scheduling.1
SLC/Ver1.0/OS CONCEPTS/Oct'9919
NetworkingNetworking
• Processors communicate with one another through various communication lines.
• The processors in the system are connected through a communication network.
SLC/Ver1.0/OS CONCEPTS/Oct'9920
Protection SystemProtection System
• Protection refers to a mechanism for controlling the access of programs, processes, or users to the resources defined by a Computer System.
• E.g. memory-addressing hardware.
SLC/Ver1.0/OS CONCEPTS/Oct'9921
Command-Interpreter SystemCommand-Interpreter System
• Command-Interpreter is the interface between the user and the OS.
• A program that reads and interprets control statements is executed automatically.
• This program is called command-interpreter, and is often known as shell.
SLC/Ver1.0/OS CONCEPTS/Oct'9922
Operating System ServicesOperating System Services
• Types of services-Program Execution.-I/O operations-File-System manipulation-Communications-Error detection-Resource allocation
SLC/Ver1.0/OS CONCEPTS/Oct'9923
Operating System ServicesOperating System Services
• Types of services-Accounting-Protection
SLC/Ver1.0/OS CONCEPTS/Oct'9924
System CallsSystem Calls
• System calls provide the interface between a process and the OS.
• Some system may allow system calls to be made directly from a higher-level language program.
• E.G. To read data from a file and to copy them to another file.
SLC/Ver1.0/OS CONCEPTS/Oct'9925
System CallsSystem Calls
• System calls can be roughly grouped into five major categories:-process control,-file manipulation-device manipulation-information maintenance-communication
SLC/Ver1.0/OS CONCEPTS/Oct'9926
System Calls-Process ControlSystem Calls-Process Control
• End, abort
• load, execute
• create process, terminate process
• get process attributes, set process attributes
• wait for time, wait event, signal event
• allocate and free memory
SLC/Ver1.0/OS CONCEPTS/Oct'9927
System Calls-File ManipulationSystem Calls-File Manipulation
• Create file, delete file
• open, close
• read, write, reposition
• get file attributes, set file attributes
SLC/Ver1.0/OS CONCEPTS/Oct'9928
System Calls-Device ManipulationSystem Calls-Device Manipulation
• request device, release device
• read, write, reposition
• get device attributes, set device attributes
• logically attach or detach devices
SLC/Ver1.0/OS CONCEPTS/Oct'9929
System Calls-Information System Calls-Information MaintenanceMaintenance
• get time or date, set time or date
• get system date, set system date
SLC/Ver1.0/OS CONCEPTS/Oct'9930
System Calls-CommunicationsSystem Calls-Communications
• create, delete communication connection
• send, receive message
• transfer status information
• attach or detach remote devices
SLC/Ver1.0/OS CONCEPTS/Oct'9931
System ProgramsSystem Programs
• It is a logical layer just above OS.
• System programs provide a more convenient environment for program development and execution.
SLC/Ver1.0/OS CONCEPTS/Oct'9932
System ProgramsSystem Programs
• They can be divided into several categories:-File Manipulation-Status information-File Modification-Programming Language Support
SLC/Ver1.0/OS CONCEPTS/Oct'9933
System ProgramsSystem Programs
• They can be divided into several categories:-Program loading and Execution-Communications-Application programs
• Perhaps the most important system program for an OS is command interpreter.
SLC/Ver1.0/OS CONCEPTS/Oct'9934
System StructureSystem Structure
• A common approach is to partition the task into small components, rather than have one monolithic system.
SLC/Ver1.0/OS CONCEPTS/Oct'9935
System Structure-Simple System Structure-Simple StructureStructure
• Commercial system doesn’t have a well-defined structure.
• Such OS started as small, simple and limited systems, and then grew beyond their original scope.
• MS-DOS is an example of such a system
SLC/Ver1.0/OS CONCEPTS/Oct'9936
System Structure-Simple System Structure-Simple StructureStructure
Application program
Resident system program
MS-DOS device driver
ROM BIOS device drivers
MS-DOS Layer structure
SLC/Ver1.0/OS CONCEPTS/Oct'9937
System Structure-Layered System Structure-Layered ApproachApproach
• Consists of breaking the OS into a number of layers, each built on top of lower layers.
• The bottom layer is the hardware; the highest(layer N) is the user interface.
SLC/Ver1.0/OS CONCEPTS/Oct'9938
System Structure-Layered System Structure-Layered ApproachApproach
Layer M-1
An OS Layer
Layer M
SLC/Ver1.0/OS CONCEPTS/Oct'9939
Virtual MachinesVirtual Machines
• Virtual Machine creates a machine for each “user” and the user can choose which OS to run on that virtual machine
• e.g Java Virtual Machine.