Operating Syatems of World

2008-03-06T03:09:00.001-08:00

operating system

- An operating system (sometimes abbreviated as "OS") is the program that, after being initially loaded into the computer by a boot program, manages all the other programs in a computer. The other programs are called applications or application programs. The application programs make use of the operating system by making requests for services through a defined application program interface (API). In addition, users can interact directly with the operating system through a user interface such as a command language or a graphical user interface (GUI).
An operating system performs these services for applications:

In a multitasking operating system where multiple programs can be running at the same time, the operating system determines which applications should run in what order and how much time should be allowed for each application before giving another application a turn.
It manages the sharing of internal memory among multiple applications.
It handles input and output to and from attached hardware devices, such as hard disks, printers, and dial-up ports.
It sends messages to each application or interactive user (or to a system operator) about the status of operation and any errors that may have occurred.
It can offload the management of what are called batch jobs (for example, printing) so that the initiating application is freed from this work.
On computers that can provide parallel processing, an operating system can manage how to divide the program so that it runs on more than one processor at a time.
All major computer platforms (hardware and software) require and sometimes include an operating system. Linux, Windows 2000, VMS, OS/400, AIX, and z/OS are all examples of operating systems.

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Operating System
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Introduction; How an OS Works; Current Operating Systems; Future Technologies
I Introduction

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Operating System (OS), in computer science, the basic software that controls a computer. The operating system has three major functions: It coordinates and manipulates computer hardware, such as computer memory, printers, disks, keyboard, mouse, and monitor; it organizes files on a variety of storage media, such as floppy disk, hard drive, compact disc, digital video disc, and tape; and it manages hardware errors and the loss of data.

II How an OS Works

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Operating systems control different computer processes, such as running a spreadsheet program or accessing information from the computer's memory. One important process is interpreting commands, enabling the user to communicate with the computer. Some command interpreters are text oriented, requiring commands to be typed in or to be selected via function keys on a keyboard. Other command interpreters use graphics and let the user communicate by pointing and clicking on an icon, an on-screen picture that represents a specific command. Beginners generally find graphically oriented interpreters easier to use, but many experienced computer users prefer text-oriented command interpreters.

Operating systems are either single-tasking or multitasking. The more primitive single-tasking operating systems can run only one process at a time. For instance, when the computer is printing a document, it cannot start another process or respond to new commands until the printing is completed.

All modern operating systems are multitasking and can run several processes simultaneously. In most computers, however, there is only one central processing unit (CPU; the computational and control unit of the computer), so a multitasking OS creates the illusion of several processes running simultaneously on the CPU. The most common mechanism used to create this illusion is time-slice multitasking, whereby each process is run individually for a fixed period of time. If the process is not completed within the allotted time, it is suspended and another process is run. This exchanging of processes is called context switching. The OS performs the “bookkeeping” that preserves a suspended process. It also has a mechanism, called a scheduler, that determines which process will be run next. The scheduler runs short processes quickly to minimize perceptible delay. The processes appear to run simultaneously because the user's sense of time is much slower than the processing speed of the computer.

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Operating systems can use a technique known as virtual memory to run processes that require more main memory than is actually available. To implement this technique, space on the hard drive is used to mimic the extra memory needed. Accessing the hard drive is more time-consuming than accessing main memory, however, so performance of the computer slows.

III Current Operating Systems

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Operating systems commonly found on personal computers include UNIX, Macintosh OS, and Windows. UNIX, developed in 1969 at AT&T Bell Laboratories, is a popular operating system among academic computer users. Its popularity is due in large part to the growth of the interconnected computer network known as the Internet. Software for the Internet was initially designed for computers that ran UNIX. Variations of UNIX include SunOS (distributed by SUN Microsystems, Inc.), Xenix (distributed by Microsoft Corporation), and Linux (available for download free of charge and distributed commercially by companies such as Red Hat, Inc.). UNIX and its clones support multitasking and multiple users. Its file system provides a simple means of organizing disk files and lets users control access to their files. The commands in UNIX are not readily apparent, however, and mastering the system is difficult. Consequently, although UNIX is popular for professionals, it is not the operating system of choice for the general public.

Instead, windowing systems with graphical interfaces, such as Windows and the Macintosh OS, which make computer technology more accessible, are widely used in personal computers (PCs). However, graphical systems generally have the disadvantage of requiring more hardware—such as faster CPUs, more memory, and higher-quality monitors—than do command-oriented operating systems.

IV Future Technologies

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Operating systems continue to evolve. A recently developed type of OS called a distributed operating system is designed for a connected, but independent, collection of computers that share resources such as hard drives. In a distributed OS, a process can run on any computer in the network (presumably a computer that is idle) to increase that process's performance. All basic OS functions—such as maintaining file systems, ensuring reasonable behavior, and recovering data in the event of a partial failure—become more complex in distributed systems.

Research is also being conducted that would replace the keyboard with a means of using voice or handwriting for input. Currently these types of input are imprecise because people pronounce and write words very differently, making it difficult for a computer to recognize the same input from different users. However, advances in this field have led to systems that can recognize a small number of words spoken by a variety of people. In addition, software has been developed that can be taught to recognize an individual's handwriting.

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Operating System
By Gary Law

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What is an operating system?
If you do not want to know, click the items below and go directly into the paper.

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[OS/2 | Mac OS |Windows NT| Windows 97]

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The most basic command software which control your computer's basic function like input and output. You can think it works like a bridge between you and your computer. If you feel headache or do not want to know anything more about what is a operating system,click here and skip to the paper body.

OK, you are tough. Let talk something more technical then: An operating system provided an environment for application to run over it. It typically included a lot of build-in functions like display a character to the screen or input a character from the keyboard. Those are most fundamental function of your computer. Because all the application software needs those most basic function to work with, so they put those most fundamental task into a program and call it Operating System.

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What are the basic functions of an operating system?

Process management
When you type in some executable command, the operating system will go and found the program which match the name you type in and execute it. That's why DOS can only run one program at one time because it takes only one command at one time. Windows and other OS contain 'schedulers', which divide the usage of the processor for different active applications and allocate CPU time to each application at milliseconds.

Memory management
Another duty of an operating system is to allocate memory to itself and other applications. Because DOS can only have 1MB of memory addressable, so the resources for other applications are limited. On the other hand, Windows and other OS can "see" all the memory installed in the computer and use them. So when you are running low in the basic memory, they will go and get those memory to create "Virtual Memory" in order to free up more memory for your applications to use.

File I/O
Other basic function of an OS is to manage your file like store, create, read, write and transfer them. High level operating like rename or delete a file are also included.

Device I/O
This is the function that your OS "talk" with your other hardware like printer, sound card and video card. To "talk" to a device, OS needs to speak the device's language. There is so many different devices out in the market and that means there is a lot of languages, so OS leads a hand by severing itself as an interpreter.

Still not headache enough? OK, try to read "Operating system: Design and Implementation" by Andrew S. Tanenbaum.. Prentice Hall, 1987. Or take CS 474 - Operating System Concepts in Fall. =)

Worked sited: PC Magazine May 14, 1996

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OS/2

What is OS/2?
OS/2 means Operating System 2. It works like other OS, for example, Windows 95, Mac OS and DOS, the main purpose of an operating system is to let you communicate with your computer. OS/2 is used under Intel platform for now.

IBM and Microsoft introduced OS/2 back in 1987, both company positioned OS/2 as the next generation of operating system and as a replacement of DOS. After a rift in 1990 between IBM and Microsoft, they separated and Microsoft go on with its Windows and IBM take over OS/2.

Hardware requirement
OS/2 needs only a minimum of 4MB of RAM and a 386 computer.

Key benefits
Today, the number of people in the world heard of Windows 95 more than the people who know who is the President of United State. Windows is the dominate operating system today but it does not mean it is the best operating system you can have. OS/2 provides a lot of features which is better than Windows 95.

OS/2 is a true 32 bit operating system. Unlike Windows 95 still has some 16 bit code in it. So OS/2 runs programs faster than Windows.
OS/2 Crash Protection prevents applications crash with each other and let your whole system goes down. It will close the bad program and let the system keep running without losing any important data.
OS/2 has a more reliable and robust environment for communication, multimedia and multitasking.
Object-oriented technology through IBM's System Object Model.
More ease-of-use features.
OS/2 selected as Overall Readers' Choice Product of the Year by InfoWorld readers in 1995.
Product Line

Last year, IBM introduced OS/2 Warp 3 for personal user and for networked business user, IBM introduced OS/2 Warp Connected which included some networking features like share folders and hard drive with other users. For work groups and small or bigbusiness, OS/2 family has OS/2 LAN Server 4.0 and OS/2 for SMP. So OS/2 is for everyone no matter you need a OS for single user or cooperation usage. According to IDC, OS/2 Warp will gain three share points of the total operating system market by the end of the year. Also, OS/2 outshipped Windows NT two to one in the server market.

The trends and the future
The latest news for OS/2 is the OS/2 Warp Server, currently under beta testing and hopefully can be out to the market by next year. Also IBM is working on the next version of the OS/2 Warp client, code name Merlin; the microkernel versions of OS/2 Warp; and IBM's integrated server series, code name Project Eagle. For the next generation of OS/2, IBM promised will have even better user interface and more intuitive. Also IBM planned to make OS/2 portable and microkernel-based in order to run under both PowerPC and Intel platforms. The first portable version will be OS/2 Warp for the PowerPC which will be shipped later this year.

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Mac OS
Mac OS Copland

What is Mac OS?
Mac OS is the operating system which run only under Mac computer environment. Mac OS has no difference in its basic function as other Intel based operating system, its purpose is work as a communicate bridge between human and computer.

What is Copland?
The latest version of Mac OS is System 7.5. Copland is the next version of Mac OS or you can call it System 8. Copland is the development name for it.

Main Features of Copland
Copland will be the next major release of the Mac OS and it will lead the operating system towards a new level. Copland offers:
Highly automatic, intelligent and the most customizable user interface to the end user.
Provide the highest system performance and stability.
Enable new and more productive ways to tightly integrating and refining System 7.5.
Designed to run the new Apple-IBM Motorola hardware reference platform (CHRP) for PowerPC.
True 32 bit multitasking, multithreading and robust working environment.
Preemptive scheduling of all system processes.
Hardware requirement:
Copland is expected to run under 8M of RAM and 40 MB of disk space. Apple also promised all the existing software for System 7.5 will have no problem run under Capland.

Benefits of Capland to organization and individuals

Easier to learn, use and support
More powerful
Smarter ways to work and communication
Safer choice
The trends and the future of Mac OS

Mac OS runs under only Mac environment and this limited its market share by the sells of Mac computer. Apple computer is currently under restructuring and having a big loss in the third quart. Intel based operating system has dominated the PC market not because they provided a better features than Mac OS, but due to the market share of the Intel based PC has sold in the world. The 'Best features' of Windows 95 like plug and play has been already existed in Mac OS ten years ago. Mac OS is just keep improving and adding new features to itself. Windows is just trying to catch up with Mac OS. The best will only get even better. The success of Mac OS will depend on the market share of the Mac machine in the world because Mac OS runs only under Mac or Power PC environment.

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Windows NT

What is Windows NT?
Windows NT works like other operating system as mention above. It designed as a high- end personal operating system. The difference between NT and the operating system above is NT offer the maximum stability and robustness. Native applications are preemptively multitasked in protected memory spaces, and Ring 3 system DLLs are protected from applications through an elaborate client/server scheme. Also NT provides a significant security features and robust new log-based file system (PC magazine, September 26). In the other words, NT provided a full protection environment for the end users.

Hardware requirement
Windows NT require 12MB of RAM as minimum, 16MB recommended, 75 MB of hard disk spaces. NT can be run under Intel, Alpha, MIPS, and PowerPC based workstation and its current versions is 3.51 and its interface looks like Windows 3.1.

Who needs Windows NT?
Windows NT actually is designed for business that depends heavily on computer and data- intensive. In a demanding environment like 'down time is money' business, for example, bank, stock market and software firm, the reliability and performance will offer a cutting advantages to their business.

Benefits of NT
You system will keep running and safely
Easy connection any where, any time because NT support more 15 networks and protocols.
Preemptive multitasking and symmetric multiprocessing.
Support wild range of hardware platform
C-2 level certifiable security.
Current trends and future
Microsoft has planned a minor upgrade for NT and it will include a Windows 95 like user interface. Also a major upgrade call Cairo is now under process and should be due around late 1996 or early 1997. At the same time, integrated with Internet in NT is expected. Also, Microsoft is pushing software developer to make sure that the software for Windows 95 should run under Windows NT. You can see Microsoft is trying to make Windows 95 as a personal version OS and NT as a business networking OS.

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Windows 97
What is Windows 97?
Windows 97 will be the next major release of Windows(another one?!). Microsoft has officially rule out the chance of having Windows 96.

(I get this picture from somewhere and it is fun!)

They will only offer a service pack to fix some bugs in Windows 95 and posted on Microsoft's Web site or available as a CD-ROM "service pack".

So what is Windows 95 then?
You dont know?? I think you have not attended the class for a while, check out our last project.

What is new for Windows 97?
You can expect to see more Internet integration like Web editing and the Microsoft's
Internet Explorer 3.0. Also Microsoft Network icon will keep staying on your desktop and MSN will become bigger and bigger.
Higher performance in multimedia. Ultimate sound like DirectX sound and video drivers will be build in Windows 97.
More merged features with Windows NT because they are sharing more code together.
Networking updates like connectable with NetWare 4.x servers and to "talk" with AS/400s.

Posted by Sathiska at 10:08 PM 0 comments
Operating Systems Lecture Notes

Introduction
History of Operating Systems
Operating Systems Structure
System Component
Operating System Services
System Calls and System Programs
Layered Approach System Design
Mechanism and Policy
Process
Definition of Process
Process State
Process Operations
Process Control Block
Threads
Solaris-2 Operating Systems
CPU/Process Scheduling
Schedule Algorithm
FCFS Scheduling
Round Robin Scheduling
SJF Scheduling
SRT Scheduling
Priority Scheduling
Multilevel Queue Scheduling
Multilevel Feedback Queue Scheduling
Interprocess Communication
Critical Section
Mutual Exclusion
Achieving Mutual Exclusion
Semaphores
Deadlock
Necessary and Sufficient Deadlock Conditions
Dealing with Deadlock Problem
Deadlock Prevention
Deadlock Avoidance
Deadlock Detection
Absolutely Important UNIX Commands
References

Operating Systems Review -- by Shikha Ghosh Gottfried.
IEEE Distributed Systems Online
Problem Reporting and Tracking System at CS Computer Systems

Links
Cryptology ePrint Archive -- provides rapid access to recent research in cryptology. Papers have been placed here by the authors and did not undergo any refereeing process other than verifying that the work seems to be within the scope of cryptology and meets some minimal acceptance criteria
How Operating Systems Work
Operating System Developers homepage
Overview of Projects on Distributed Operating Systems -- at Department of CS, U. of Ulm.
Review of Operating Systems
Virtual Network Computing - VNC -- Access Personal Computer remotely
Win2VNC -- a dual-screen hack for Windows. This program will let you use two screens on two different computers as if they were connected to the same computer. It even works between different operating systems.
Books & Tutorials
Cryptography and Network Security by William Stallings | Resources
Multithreaded Programming with ThreadMentor: A Tutorial by C.-K. Shene
Operating System Design & Implementation - Tutorial -- by Mohan Raj Dhanagopal.
Operating System Concepts Sixth Edition by Abraham Silberschatz , Peter Baer Galvin and Greg Gagne
Operating Systems, Fourth Edition by William Stallings | Resources
Nachos
Guide to Nachos 5.0j by Dan Hettena & Rick Cox -- Nachos and Java.
Nachos -- General Nachos documentation at U. of Washington.
Nachos User-Level Remote Debugging With GDB -- at U. of Kansas.
Reading Nachos Source Code -- by Michael O'Donnell, University of Chicago
Road Map Through Nachos -- by Thomas Narten at Duke U.
High-level overview of the source code which can be used as companion to overcome the initial learning curve encountered when learning and using the system.
Salsa -- An Operating Systems Tutorial -- by Archna Kalra at U.Mass Amherst.
Programming
cpp-home -- wide range of C++ tutorials and codes.
cprogramming.com
C-lesson by Christopher Sawtell -- This archive contains a complete course to learn the 'C' computer language itself.
LEARN C/C++ TODAY -- Annotated collection of tutorials on both C and C++.

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Process Creation

In general-purpose systems, some way is needed to create processes as needed during operation. There are four principal events led to processes creation.

System initialization.
Execution of a process Creation System calls by a running process.
A user request to create a new process.
Initialization of a batch job.

Foreground processes interact with users. Background processes that stay in background sleeping but suddenly springing to life to handle activity such as email, webpage, printing, and so on. Background processes are called daemons. This call creates an exact clone of the calling process.

A process may create a new process by some create process such as 'fork'. It choose to does so, creating process is called parent process and the created one is called the child processes. Only one parent is needed to create a child process. Note that unlike plants and animals that use sexual representation, a process has only one parent. This creation of process (processes) yields a hierarchical structure of processes like one in the figure. Notice that each child has only one parent but each parent may have many children. After the fork, the two processes, the parent and the child, have the same memory image, the same environment strings and the same open files. After a process is created, both the parent and child have their own distinct address space. If either process changes a word in its address space, the change is not visible to the other process.

Following are some reasons for creation of a process

User logs on.

User starts a program.

Operating systems creates process to provide service, e.g., to manage printer.

Some program starts another process, e.g., Netscape calls xv to display a picture.

Process Termination

A process terminates when it finishes executing its last statement. Its resources are returned to the system, it is purged from any system lists or tables, and its process control block (PCB) is erased i.e., the PCB's memory space is returned to a free memory pool. The new process terminates the existing process, usually due to following reasons:

Normal Exist Most processes terminates because they have done their job. This call is exist in UNIX.
Error Exist When process discovers a fatal error. For example, a user tries to compile a program that does not exist.
Fatal Error An error caused by process due to a bug in program for example, executing an illegal instruction, referring non-existing memory or dividing by zero.
Killed by another Process A process executes a system call telling the Operating Systems to terminate some other process. In UNIX, this call is kill. In some systems when a process kills all processes it created are killed as well (UNIX does not work this way).

Process States

A process goes through a series of discrete process states.

New State The process being created.
Terminated State The process has finished execution.
Blocked (waiting) State When a process blocks, it does so because logically it cannot continue, typically because it is waiting for input that is not yet available. Formally, a process is said to be blocked if it is waiting for some event to happen (such as an I/O completion) before it can proceed. In this state a process is unable to run until some external event happens.
Running State A process is said t be running if it currently has the CPU, that is, actually using the CPU at that particular instant.
Ready State A process is said to be ready if it use a CPU if one were available. It is runable but temporarily stopped to let another process run.
Logically, the 'Running' and 'Ready' states are similar. In both cases the process is willing to run, only in the case of 'Ready' state, there is temporarily no CPU available for it. The 'Blocked' state is different from the 'Running' and 'Ready' states in that the process cannot run, even if the CPU is available.