Operating System Classification and Structure
Q?what are the Common System Components
/> Process Management
/> Main Memory Management
/> Secondary-Storage Management
/> I/O System Management
/> File Management
/> Protection System
/> Networking
/> Command-Interpreter System
Q?>what is process
/> A process is a program in
execution. A process needs certain resources
like CPU time, memory,
files, and I/O
devices, to accomplish its task
Q?>Who is responsible for process management
/> The OS is responsible for this.
It does process management performing following activities of process
creation and deletion,
process suspension and
resumption and lastly also
providing some mechanism for process synchronization
and process communication.
Q?>What kind of activities are performed by OS for Main-Memory Management
/> OS performs following tasks
=> it keeps track of which
part of memory are currently being used and by whom
=> decide which process to load
when memory space becomes available
=> allocate and deallocate memory space as needed
Q?why we use secondary-storage
/> since the main memory is volatile
and very small to accommodate all the data and programs permanently,
we use this secondary-storage to back up the main memory.
Q?what OS does to do secondary-storage management
/> OS performs following tasks
=> Free space management
=> storage allocation
=> Disk scheduling
Q?what OS does to do I/O system management
/> OS has following tools for I/O management
=> there is a buffer-caching system :
=> there is also a general
device-driver interface
=> drivers for specific hardware devices
Q?what is file
/> it is a collection of related information defined by its creator.File
can represent both program and data.
Q?How OS manages file
/> it does following activities
=> file creation and deletion
=> directory creation and deletion
=> support of primitive for
mainpulating files and directories
=> map files to secondary storage
=> backup the file on nonvolatile storage
Q?How does the OS assure the protection of the System
/> OS performs following tasks :
=> allocates resources to multiple users or multiple
jobs running at same time
=> it controls the access to System and User resources by distinguishing
between the authorized and unauthorized usage.
=> it also specifies the controls to be imposed on programs, processes
or users
=> keep tracks of and record
which users use how much and what kind of computer resources for
account billing or for statistics
=> it provides a means of enforcement to ensure that all accessed system
resources is controlled
Q?What is Networking(Distributed Systems)
/> In ditributed system the each processors has their
own local memory and the do not share memory or a clock.
/> here the systems are connected through communication
network
/> it provides access to various system resources which cause :
=> computational speed-up, increased
data availability, inhanced reliability
Q?What is Command-Interpreter System
/> There are many commands
given to OS by control
statements which does process
creation, management, I/O handling, secondary-storage management,
main-memory management, file-system access, system-protection,
networking.
The tool that reads and interprets
this control statements are called Control-card
interpreter Or Command-line interpreter or shell(IN Unix)
Q?What are System Calls
/> Running Program ||System Calls|| Operating system
Q?How do we pass parameters between a running program and the Operating
System
/> Pass parameters in Registers
/> Store the parameters in a table in memory, and the table
address is passed as a parameter in a register
/> Push is performed by program
to store the parameters onto the stack while Pop
is performed by operating system to use the parameter from stack.
Q?What are System Programs
/> OS is defined by system programs, not actually by system calls.
This provides the suitable environment
for program development and execution. They are divided into :
/> File manipulation
/> Status information
/> File modification
/> Programming language support
/> Program loading and execution
/> Communication
/> Application programs
Q?what is MS-DOS System Structure
/> MS-DOS has the simple approach and written to provide the
most functionality in the least space.
/> not divided into modules (interfaces and level of functionality not
seperated)
Q?what is Unix System Structure
/> Unix Operating system are
developed by simple approach
and consist of two seperate parts
/1> System programs :
/2> The kernel :
The Unix System Structure is :
| User |
| Shell
and Commands : compilers and interpreters, system libraries |
| Kernel
interface (System Call) |
| Signal-terminal,disk,tape,..driver-device...,
file system, cpu scheduling – memory paging |
| Hardware
Kernel interface |
| Terminal
controller , disk controller, memory controller
|
Q?what are System Structure – Layered Approach
/> The OS is divided into number of layers.
/> Each layer are built on top of lower layer i.e. bottom layer (layer
0),is the hardware and the highest layer (layer N) is the user interface
/> The layers are selected as such that each uses functions(operations) and
services of only lower-level layers.
| Layer5
: user programs |
| Layer4
: buffering for input and output |
| Layer3
: operator-console device driver |
| Layer2
: memory management
|
| Layer1
: CPU scheduling |
| Layer0
: hardware |
Q?what are Virtual Machines
/> This provides an interface identical to the underlying bare hardware
i.e. it treats hardware and the
operating system kernel as though they were all hardware.
Thus, the OS creates the illusion
of multiple processes, each executing on its own processor
with its own virtual memory.
Q?What is MicroKernel
/> It is the near-minimum amount of
software that can provide the mechanism needed to implement an OS.
This mechanism include low-level address space management, thread
management and inter-process communication (IPC).
Microkernel consist of wakeup driver
which wakes up device driver and it also consist of interrupt
handler to handle I/O completion interrupt.
Q?what are the System Design and Implementation criteria
/> we have to design the OS considering two basic concepts :
/1> user goal : OS must be
convenint to use, easy to learn, reliable, safe and fast
/2> System goal : OS must be
easy to design, implement, and maintain, as well as flexible,
reliable, error-free and efficient.
YouTube :
https://www.youtube.com/watch?v=0mNcX1Elrp4&feature=youtu.be
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