In computing, multitasking is a method by which multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is actively executing instructions for that task. Multitasking solves the problem by scheduling which task may be the one running at any given time, and when another waiting task gets a turn. The act of reassigning a CPU from one task to another one is called a context switch. Operating systems may adopt one of many different scheduling strategies, which generally fall into three categories that are multiprogramming, time-sharing and real-time systems.
In multiprogramming systems, the running task keeps running until it performs an operation that requires waiting for an external event (e.g. reading from a tape) or until the computer's scheduler forcibly swaps the running task out of the CPU. Multiprogramming systems are designed to maximize CPU usage. Also in multiprogramming, several programs are in memory concurrently; the system switches among the programs for efficient processing, and minimal idle time. The main advantage of multiprogramming makes efficient use of the CPU by overlapping the demands for the CPU and its I/O devices from various users. It attempts to increase CPU utilization by always having something for the CPU to execute.
In time-sharing systems, the running task is required to relinquish the CPU, either voluntarily or by an external event such as a hardware interrupt. Time sharing systems are designed to allow several programs to execute apparently simultaneously. Time-sharing is using scheduling and multiprogramming to provide an economical interactive system of two or more users. The main advantage of time-share system is when the interaction with computer while program is running, short response times (usually less than 10 seconds). The expression 'time sharing' was usually used to designate computers shared by interactive users at terminals, such as IBM's TSO, and VM/CMS. In real-time systems, some waiting tasks are guaranteed to be given the CPU when an external event occurs.
In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems. The two problems are first is stealing or copying one’s programs or data and second is using system resources (CPU, memory, disk space, peripherals) without proper accounting. Stealing or copying user’s files is when writing over another program’s (belonging to another user or to the OS) area in memory and the user may modify the data which is required by another user. One user can copy another user's program / memory space. This could be very detrimental if, for example, an administrator was running a decryption protocol, and another user stole the decryption program and/or key. Using system resources (CPU, disk space) without proper accounting is causing the printer to mix output by sending data while some other user’s file is printing and one user may use the resources but charge expenses to some another user. Resource usage may not be completely controlled, and could cause deadlock for certain users. For example, if user A had resource 1 and was waiting for resource 2, and user B had resource 2 and was waiting for resource 1, deadlock would occur and neither user would be able to make progress in their program, no matter how many time slots they were allocated.
Can we ensure the same degree of security in a time-share machine as we have in a dedicated machine? Probably not, since any protection scheme devised by man can inevitably be broken by him, and the more complex the scheme, the more difficult it is to feel confident of its correct implementation. It is not as secure and the real question is "How much less secure is it, and does the added exposure outweigh the cost savings for this application”. If you're working with nuclear launch codes, it's going to be hard to argue for saving money by time-sharing. If it's just a bank's database, time-sharing makes sense (and you get added security there because you can have the one guy update software for patching and everybody is running the new software, rather than having 1,000 desktops not all of which are patched). But a case can be made that to secure a system, multi-user operation is required, in order to support multiple roles (security auditor, and user) - dedicated operations don't provide a suitable audit trail.
It's the rare multiprogramming system these days where the operating system is the weak link - even Windows provides enough security.
Monday, December 6, 2010
WHEN USING HANDHELD COMPUTER. . . .
A mobile device is known as handheld computer that is a pocket-sized computing device, typically having a display screen with touch input and/or a miniature keyboard. In the case of the personal digital assistant (PDA) the input and output are often combined into a touch-screen interface. Smart phones and PDAs are popular amongst those who require the assistance and convenience of certain aspects of a conventional computer, in environments where carrying one would not be practical.
The two professionals that I would put forward a theory about how that person might use a hand held computer in their work were a newspaper reporter and a manager in a supermarket.
A newspaper reporter gather and analyze facts about current events through interviews, investigations, or observations and write stories describing the events, background, meaning, and effects. They are assigned breaking news developments such as disasters, crime, and human interest. They take notes or use a tape recorder while covering a story. They check reference materials such as books, news files, and public records including criminal and civil court files for additional relevant facts. Basic tasks of reporters involve viewing events objectively, reporting them accurately, and explaining their significance. This person might use a handheld computer in their work by making their news report quickly, taking pictures of evidences to their story, and easy to carry because of its size, small. It would help them to work simply that makes them more interested for their work, help them be more organized and to more efficiently process newspaper ad sales. It helps them to record the details easily, browse in a web quickly and take pictures or videos that will provide them for proving or for some evidences. Using this handheld computer for a newspaper reporter they can make their feature story and newspaper pictures easy, no hurry for editing and just send their finished story to their publishing company. Also, using handheld computer is a great potential resource for them because of its versatility and portability.
Manager in a supermarket is the one who is in-charge in supermarket that sells food, drink, products for cleaning the house etc. He/she supervise of the workers within the supermarket day to day. The manager might use the handheld computer in their work by able to make telephone calls, make payments and can use it to store all information that they have in their briefcases, and the device is assisted by wireless networking, where it is an essential step in making electronic document exchange, electronic communication and electronic commerce. It helps them make their work easier and efficient like what a newspaper reporter does. The device is a small portable computer with a smart card and communications device that can replace a cash, cheque book, passport, keys, diary, phone/pager and maps. Using the handheld computer, the manager could send e-mail and to access information services and data networks. Handheld computer is truly a personal machine that for instance, it contains sensitive information or store the owner’s private keys or electronic money. The device helps the manager to be more organized with his/her work which can access to their business data and applications.
The two professionals that I would put forward a theory about how that person might use a hand held computer in their work were a newspaper reporter and a manager in a supermarket.
A newspaper reporter gather and analyze facts about current events through interviews, investigations, or observations and write stories describing the events, background, meaning, and effects. They are assigned breaking news developments such as disasters, crime, and human interest. They take notes or use a tape recorder while covering a story. They check reference materials such as books, news files, and public records including criminal and civil court files for additional relevant facts. Basic tasks of reporters involve viewing events objectively, reporting them accurately, and explaining their significance. This person might use a handheld computer in their work by making their news report quickly, taking pictures of evidences to their story, and easy to carry because of its size, small. It would help them to work simply that makes them more interested for their work, help them be more organized and to more efficiently process newspaper ad sales. It helps them to record the details easily, browse in a web quickly and take pictures or videos that will provide them for proving or for some evidences. Using this handheld computer for a newspaper reporter they can make their feature story and newspaper pictures easy, no hurry for editing and just send their finished story to their publishing company. Also, using handheld computer is a great potential resource for them because of its versatility and portability.
Manager in a supermarket is the one who is in-charge in supermarket that sells food, drink, products for cleaning the house etc. He/she supervise of the workers within the supermarket day to day. The manager might use the handheld computer in their work by able to make telephone calls, make payments and can use it to store all information that they have in their briefcases, and the device is assisted by wireless networking, where it is an essential step in making electronic document exchange, electronic communication and electronic commerce. It helps them make their work easier and efficient like what a newspaper reporter does. The device is a small portable computer with a smart card and communications device that can replace a cash, cheque book, passport, keys, diary, phone/pager and maps. Using the handheld computer, the manager could send e-mail and to access information services and data networks. Handheld computer is truly a personal machine that for instance, it contains sensitive information or store the owner’s private keys or electronic money. The device helps the manager to be more organized with his/her work which can access to their business data and applications.
THE FIVE TYPES OPERATING SYSTEMS
--->Batch Systems
VAX-11/780
--->Interactive Systems
INTERACTIVE UNIX System V/386
INTERACTIVE UNIX System V/386 is a port of the UNIX System V operating system for Intel x86 processors. The system was first released by INTERACTIVE Systems Corporation (ISC) as 386/ix in 1985. At that time it was based on System V.3.0. Later versions were based on System V.3.2. Sun Microsystems acquired ISC in 1992 from its parent Eastman Kodak; the last version was "System V/386 Release 3.2 Version 4.1.1" released in July 1998. Official support ended in July 2006, 5 years after Sun withdrew the product from sale. Until version ISA 3.0.1, INTERACTIVE UNIX supported only 16 MB of RAM. In the next versions, it supported 256MB RAM and PCI bus. EISA versions always support 256MB RAM.
--->Real-time systems
xPC Target™
xPC Target™ is a real-time software environment from MathWorks. Together with x86-basedreal-time systems, it enables engineers to simulate and test Simulink and Stateflowmodels in an early-as-possible stage in real-time on the physical hardware under test. xPC Target™ enables you to execute Simulink® and Stateflow®models on a target computer for rapid control prototyping, hardware-in-the-loop (HIL) simulation, and other real-time testing applications. It provides a library of drivers, a real-time kernel, and a host-target interface for real-time monitoring, parameter tuning, and data logging. The recommended development process is to design or model an algorithm or set of algorithms meant to be implemented in hardware in Simulink. For a complete, fully assembled, real-time testing solution, xPC Target Turnkey combines xPC Target with a variety of high-performance real-time target computers.
The Key Features of xPC Target™
--->Hybrid Systems
Windows 7
Screenshot of Windows 7 Ultimate Edition
Windows 7 is the latest release of Microsoft Windows, a series of operating systems produced by Microsoft for use on personal computers, including home and business desktops, laptops, netbooks, tablet PCs, and media center PCs. Windows 7 was released to manufacturing on July 22, 2009, and reached general retail availability on October 22, 2009, less than three years after the release of its predecessor, Windows Vista. Windows 7's server counterpart, Windows Server 2008 R2, was released at the same time.
Unlike its predecessor, Windows Vista, which introduced a large number of new features, Windows 7 was intended to be a more focused, incremental upgrade to the Windows line, with the goal of being compatible with applications and hardware which Windows Vista was not at the time. Presentations given by Microsoft in 2008 focused on multi-touch support, a redesigned Windows shell with a new taskbar, referred to as the Superbar, a home networking system called HomeGroup, and performance improvements. Some standard applications that have been included with prior releases of Microsoft Windows, including Windows Calendar, Windows Mail, Windows Movie Maker, and Windows Photo Gallery, are not included in Windows 7; most are instead offered separately at no charge as part of the Windows Live Essentials suite.
Maximum limits on physical memory (RAM) that Windows 7 can address vary depending on both the Windows version and between 32-bit and 64-bit versions. The maximum quantity of cores in 1 physical processor of a PC that Windows 7 supports is: 32 for 32-bit, 256 for 64-bit. The maximum quantity of physical processors of a PC that Windows supports is: 2 for Professional, Enterprise, and Ultimate; 1 for Starter, Home Basic, and Home Premium.
--->Embedded Systems
Amora Theme for Symbian OS 9.1 (s60 3rd)
Symbian OS is one of Nokia's mobile operating systems for mobile devices and smartphones, with associated libraries, user interface, frameworks and reference implementations of common tools, originally developed by Symbian Ltd. It is a descendant of Psion's EPOC and runs exclusively on ARM processors, although an unreleased x86 port existed.
Symbian features pre-emptive multitasking and memory protection, like other operating systems (especially those created for use on desktop computers). EPOC's approach to multitasking was inspired by VMS and is based on asynchronous server-based events.
Symbian OS was created with three systems design principles in mind:
VAX-11/780
The "native" VAX operating system is DEC's VAX/VMS (renamed to OpenVMS in 1991 or 1992 when it was ported to Alpha, "branded" by the X/Open consortium, and modified to comply with POSIX standards[2]). The VAX architecture and VMS operating system were "engineered concurrently" to take maximum advantage of each other, as was the initial implementation of the VAXcluster facility. Other VAX operating systems have included various releases of BSD UNIX up to 4.3BSD, Ultrix-32, VAXELN and Xinu. More recently, NetBSD and OpenBSD support various VAX models and some work has been done on porting Linux to the VAX architecture.
The VAX-11/780 was the first VAX model sold, which was introduced on October 25, 1977 at the Digital Equipment Corporation's Annual Meeting of Shareholders. Bill Strecker, C. Gordon Bell's doctoral student at Carnegie-Mellon University, was responsible for the architecture. The VAX-11/780 was used as a baseline in CPU benchmarks because its speed was about one MIPS. The actual number of instructions executed in 1 second was about 500,000. One VAX MIPS was the speed of a VAX-11/780; a computer performing at 27 VAX MIPS would run the same program roughly 27 times faster than the VAX-11/780. Within the Digital community the term VUP (VAX Unit of Performance) was the more common term, because MIPS do not compare well across different architectures. The related term cluster VUPs was informally used to describe the aggregate performance of a VAXcluster. The performance of the VAX-11/780 still serves as the baseline metric in the BRL-CAD Benchmark, a performance analysis suite included in the BRL-CAD solid modeling software distribution. The VAX-11/780 included a subordinate stand-alone LSI-11 computer that performed booting and diagnostic functions for the parent computer. This was dropped from subsequent VAX models. Enterprising VAX-11/780 users could therefore run programs under three different Digital Equipment Corporation operating systems, VMS and using compatibility mode, RSX-11M, and RT-11 using this subordinate computer.--->Interactive Systems
INTERACTIVE UNIX System V/386
INTERACTIVE UNIX System V/386 is a port of the UNIX System V operating system for Intel x86 processors. The system was first released by INTERACTIVE Systems Corporation (ISC) as 386/ix in 1985. At that time it was based on System V.3.0. Later versions were based on System V.3.2. Sun Microsystems acquired ISC in 1992 from its parent Eastman Kodak; the last version was "System V/386 Release 3.2 Version 4.1.1" released in July 1998. Official support ended in July 2006, 5 years after Sun withdrew the product from sale. Until version ISA 3.0.1, INTERACTIVE UNIX supported only 16 MB of RAM. In the next versions, it supported 256MB RAM and PCI bus. EISA versions always support 256MB RAM.
--->Real-time systems
xPC Target™
xPC Target™ is a real-time software environment from MathWorks. Together with x86-basedreal-time systems, it enables engineers to simulate and test Simulink and Stateflowmodels in an early-as-possible stage in real-time on the physical hardware under test. xPC Target™ enables you to execute Simulink® and Stateflow®models on a target computer for rapid control prototyping, hardware-in-the-loop (HIL) simulation, and other real-time testing applications. It provides a library of drivers, a real-time kernel, and a host-target interface for real-time monitoring, parameter tuning, and data logging. The recommended development process is to design or model an algorithm or set of algorithms meant to be implemented in hardware in Simulink. For a complete, fully assembled, real-time testing solution, xPC Target Turnkey combines xPC Target with a variety of high-performance real-time target computers.
The Key Features of xPC Target™
- Real-time execution of Simulink and Stateflow models on a target computer via an optimized real-time kernel
- Support for target computer hardware, including PMC, PCI, PCIe, cPCI, and PC104 form factors
- Support for numerous I/O modules, including analog I/O, digital I/O, pulse train generation and capture, and shared memory
- Support for communication protocols and data buses, including serial, UDP/IP, CAN, J1939, ARINC 429, and MIL-STD-1553
- Tools for real-time monitoring, parameter tuning, and data logging
- Standalone operation using xPC Target Embedded Option
- Open APIs (Visual Basic, C/C++, Java, and .NET) for programmatically developing user interfaces
--->Hybrid Systems
Windows 7
Windows 7 is the latest release of Microsoft Windows, a series of operating systems produced by Microsoft for use on personal computers, including home and business desktops, laptops, netbooks, tablet PCs, and media center PCs. Windows 7 was released to manufacturing on July 22, 2009, and reached general retail availability on October 22, 2009, less than three years after the release of its predecessor, Windows Vista. Windows 7's server counterpart, Windows Server 2008 R2, was released at the same time.
Unlike its predecessor, Windows Vista, which introduced a large number of new features, Windows 7 was intended to be a more focused, incremental upgrade to the Windows line, with the goal of being compatible with applications and hardware which Windows Vista was not at the time. Presentations given by Microsoft in 2008 focused on multi-touch support, a redesigned Windows shell with a new taskbar, referred to as the Superbar, a home networking system called HomeGroup, and performance improvements. Some standard applications that have been included with prior releases of Microsoft Windows, including Windows Calendar, Windows Mail, Windows Movie Maker, and Windows Photo Gallery, are not included in Windows 7; most are instead offered separately at no charge as part of the Windows Live Essentials suite.
Maximum limits on physical memory (RAM) that Windows 7 can address vary depending on both the Windows version and between 32-bit and 64-bit versions. The maximum quantity of cores in 1 physical processor of a PC that Windows 7 supports is: 32 for 32-bit, 256 for 64-bit. The maximum quantity of physical processors of a PC that Windows supports is: 2 for Professional, Enterprise, and Ultimate; 1 for Starter, Home Basic, and Home Premium.
--->Embedded Systems
Symbian OS is one of Nokia's mobile operating systems for mobile devices and smartphones, with associated libraries, user interface, frameworks and reference implementations of common tools, originally developed by Symbian Ltd. It is a descendant of Psion's EPOC and runs exclusively on ARM processors, although an unreleased x86 port existed.
Symbian features pre-emptive multitasking and memory protection, like other operating systems (especially those created for use on desktop computers). EPOC's approach to multitasking was inspired by VMS and is based on asynchronous server-based events.
Symbian OS was created with three systems design principles in mind:
- the integrity and security of user data is paramount,
- user time must not be wasted, and
- all resources are scarce.
Monday, November 22, 2010
November 23,2010
We are not living for nothing. We live because we have our mission and in order to go on for our journey, we must first face obstacles, challenges in life. In life, we learn to sacrifice and learn things that will help us and make us to be a better person. That's why we need to value life, live it happily, don't waste time that until such time you just know that you lost someone. Hope we learn to value everything especially in simple things.
Searching....
I am now searching for the types of OS. It's so hard because I have time pressured...,hmm...I hope I can finish it today so that I can start my next case study...,Help me God :)
MY BLOG.
char..,naa naku blog..,hehe
..,pwede maulaw..,by the way, maski hagu na aku life, still go on, no choice eh..,hmm
..,pwede maulaw..,by the way, maski hagu na aku life, still go on, no choice eh..,hmm
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