MCSE Training Guide: Windows Architecture and Memory

Transcription

1 MCSE Training Guide: Windows Ch 2 -- Architecture and Memory Page 1 of 13 MCSE Training Guide: Windows Architecture and Memory This chapter wi hep you prepare for the exam by covering the foowing objectives: Compare and contrast the memory usage of a Microsoft MS-DOS-based appication, a 16-bit Windows-based appication, and a 32-bit Windows-based appication operating in Windows 95 You might reca the od wives tae that a bride shoud wear "something od, something new, something borrowed, something bue" to ensure a happy marriage. Windows 95 is simiar to that bride s wedding appare. It has features and capabiities of the oder versions of both DOS and Windows. Windows 95 incudes many great new features that were not present in previous versions of either DOS or Windows. Windows 95 borrows heaviy from the 32-bit architecture of Windows NT. Finay, Windows 95 wi not make you bue when you re trying to run most of your oder DOS and 16-bit Windows appications. This chapter gives you an overview of the architecture of Windows 95, and how Windows 95 manages memory. In this chapter, you wi earn about the foowing: Windows 95 System Services Windows 95 virtua machines Windows 95 virtua memory Windows 95 task scheduing and mutitasking Windows 95 interna messaging Appication memory usage comparison Understanding Ring 0 and Ring 3 Windows 95 uses an Inte 386 or better processor to support mutipe priviege eves for executabe code. Of the four eves, or "rings," in the Inte 386 protection mode, Windows 95 uses Rings 0 and 3. These rings provide different eves of protection and privieges. The ower the ring number, the higher the eves of protection and privieges. Figure 2.1 iustrates the ayout of the ring architecture for Windows 95. Components of Windows 95 are divided between Ring 0 and Ring 3 code. Each ring offers a different eve of system protection. The Ring 0 code is protected by the Inte processor architecture and consists of a the ow-eve operating System Services, such as the Fie Management subsystem and the Virtua Machine fie://i:\chapters\z\zc676.htm 3/21/01

2 MCSE Training Guide: Windows Ch 2 -- Architecture and Memory Page 2 of 13 Manager subsystem. The Ring 3 code is protected from other running processes by protection services provided in the operating system. The Ring 3 code runs the System Virtua Machine and any Virtua DOS Machines. FIGURE 2.1 The ring architecture of Inte 386 or better processors. Ring 0 components are protected by the processor architecture. The processor prevents the component code from writing over another existing component s code. These Ring 0 components are the core eements of Windows 95. They can run a privieged operations, incuding direct communication with the hardware components. They have access to the entire computer system. A bad component in Ring 0 can bring down the computer system; therefore, every component running in Ring 0 needs to be extremey reiabe. A of the ow-eve Windows 95 core components run in Ring 0. Ring 3 components have no processor protection; the operating system must provide protection for Ring 3 components. Ring 3 components cannot write to the hardware components. They must communicate to a Ring 0 process to write to a hardware component. A bad appication component in Ring 3 does not necessariy bring down the computer system. Usuay you can recover from any probems associated with a Ring 3 component by simpy cosing that component. Appications and non-critica System Services of Windows 95 components run on Ring 3. Windows 95 Components Understanding how the various components of an operating system, such as Windows 95, fit together can be difficut. The Windows 95 Resource Kit and the New Riders book Inside Windows 95 provide better reference materia on this subject. This section provides some perspective on Windows 95 components. Figure 2.2 contains a diagram of the Windows 95 components that run in both Ring 0 and Ring 3 of the Inte 386 protection mode. Ring 3 hosts the virtua machines (VMs) in which MS-DOS, Windows 16-bit, and Windows 32-bit appications execute. The MS-DOS appications a run in separate VMs, known as Virtua DOS Machines (VDMs). A Windows appications, whether Windows 16-bit or 32-bit, execute in the System VM. The System VM aows mutipe concurrent appications to run. Whereas a Windows 32-bit appications are isoated in private address spaces, a the active Windows 16-bit appications share a singe, common address space. These appications are managed by the Virtua Machine Manager (VMM) in Ring 0. As a resut, the Windows 16-bit appications operate much as they do under Windows 3.1, where they are cooperativey mutitasked. Windows 32-bit and MS-DOS appications are preemptivey mutitasked. (See Chapter 1, "Panning and Instaation," for a discussion of cooperative and preemptive mutitasking.) The centra components of the Windows graphica environment aso run as System Services. These incude Kerne, GDI, and User. The next section ooks at these System Services in greater detai. FIGURE 2.2 Windows 95 system architecture. Ring 0 hosts both the VMM subsystem and the Fie Management subsystem. The VMM subsystem provides the resources needed for each appication and system process running on the computer, incuding memory management and task scheduing. Virtua Device Drivers (VxDs) are 32-bit, fie://i:\chapters\z\zc676.htm 3/21/01

3 MCSE Training Guide: Windows Ch 2 -- Architecture and Memory Page 3 of 13 protected-mode drivers that manage a system resource, such as a hardware device or instaed software. They aow more than one appication to use the resource at the same time. The Fie Management subsystem features an Instaabe Fie System Manager, which supports mutipe fie systems, such as VFAT, CDFS, and Network redirectors. The Instaabe Fie System Manager aso supports an open fie system architecture, so future fie systems can be added ater. The Bock I/O subsystems are responsibe for the interaction with the physica storage devices. Windows 95 System Services Much of the code within Windows 95 is either new 32-bit code or oder Windows 3.x code rewritten as 32-bit code, rather than 16-bit code. Windows 95, however, is not competey a 32-bit operating system. Windows 95 strikes a baance between three requirements: deivering compatibiity with existing appications and drivers, decreasing the size of the operating system to run on 4 MB of RAM, and offering improved system performance. To provide this baance, Windows 95 uses a combination of both 32-bit and 16-bit code. Windows 95 empoys 32-bit code wherever 32-bit code significanty improves performance without sacrificing appication compatibiity. Existing 16-bit code is retained where it is required to maintain compatibiity, or where 32-bit code woud increase memory requirements without significanty improving performance. A of the I/O subsystems and device drivers in Windows 95, such as networking and fie systems, are fuy 32 bit. A memory management and scheduing components, such as Kerne and Virtua Memory Manager, are 32 bit as we. Figure 2.3 depicts the reative distribution of 32-bit code versus 16-bit code present in each of the Windows 95 System Services. The sizes of the boxes in the figure iustrate the number of ines of code for each 16-bit and 32-bit version of the three System Services fies. Three sets of fies constitute the Windows 95 System Services: Kerne, Graphics Device Interface (GDI), and User: The Kerne (KRNL386.EXE and KERNEL32.DLL) provides base operating system functions, incuding fie I/O services, virtua memory management, appication management, and task scheduing. The GDI (GDI.EXE and GDI32.DLL) contros the graphics operations that create images on the system dispay and other devices, such as printers. The User (USER.EXE and USER32.DLL) creates and maintains windows on-screen and carries out a requests to create, move, size, or remove a window. The User aso handes requests regarding the icons and other components of the user interface. It aso directs input to the appropriate appication from the keyboard, mouse, and other input sources. FIGURE 2.3 Ring 3 System Services. As iustrated, most of the System Services provided by the operating system Kerne are provided as 32-bit code. The remaining 16-bit code consists of hand-tuned assemby anguage, deivering performance that rivas the 32-bit code. Many functions provided by the GDI have been moved to 32- bit code, incuding the spooer and printing subsystem, the font rasterizer, and the drawing operations performed by the graphics DIB engine. Roughy haf of a GDI cas are handed in the 32-bit code. The 16-bit code for GDI contains most of the drawing routines. Much of the window management fie://i:\chapters\z\zc676.htm 3/21/01

4 MCSE Training Guide: Windows Ch 2 -- Architecture and Memory Page 4 of 13 User code sti remains 16-bit to maintain Windows 16-bit appication compatibiity. The Thunk Layer, shown in figure 2.3, makes reference to the term thunking. This specia term describes how 16-bit code components communicate with their 32-bit code component counterparts. The thunking process transates memory addresses between 32-bit cas and 16-bit cas. A sight performance degradation occurs in the transation, athough it is hardy noticeabe. In genera, the 32-bit code is provided in Windows 95 to maximize the performance and reiabiity of the system. The 16-bit code baances the requirements for reducing the size of the operating system whie maintaining compatibiity with existing appications and drivers. Windows 95 Virtua Machines A appications and dynamic ink ibrary (DLL) programs run in Ring 3. They execute in a virtua machine (VM), which ooks ike a separate computer from the appication s perspective. A VM is an environment created by Windows 95 to simuate a compete computer, with a the resources avaiabe to a physica computer, such as hard disk controers and a timer. The VMM creates and maintains the virtua machine environments and provides each appication the system resources needed to run the system. The System VM runs the System Services as we as a Windows 32-bit and 16-bit appications. The 16-bit Windows appications a run in a shared, common address space. Each 32-bit Windows appication runs in its own private address space. Each MS-DOS appication runs in its own separate VDM. The Virtua Machine Manager, in addition to creating and maintaining these virtua machines, provides severa key services: Memory Management. Contros the 4 GB of addressabe virtua memory, paging from RAM to the hard disk, and performs memory address transation. This is discussed in the foowing section, "Windows 95 Virtua Memory." Task Scheduing and Mutitasking. Aocates system resources and time to the appications and other processes running on the computer. These are discussed in the section "Windows 95 Task Scheduing and Mutitasking" ater in this chapter. MS-DOS Mode support. For MS-DOS appications that need excusive access to system resources. This specia mode of Windows 95 operations shoud not be confused with the VDM. It is a separate and excusive MS-DOS operating environment, and is discussed further in Chapter 8, "Running Appications." Windows 95 Virtua Memory Windows 95 uses two types of memory: physica and virtua. Most users are famiiar with the amount of RAM, or physica memory, on the computer itsef. As mentioned in Chapter 1, the minimum requirement for RAM on a computer running Windows 95 is 4 MB. The recommended amount of RAM is at east 8 MB. The author even suggests 16 MB of RAM for Windows 95. With Windows 95, the operating system uses a of the avaiabe physica memory on the computer. You can overcome hardware memory imitations through the use of virtua memory. The Windows 95 operating system uses a fat memory mode, which everages off the Inte 386 or fie://i:\chapters\z\zc676.htm 3/21/01

5 MCSE Training Guide: Windows Ch 2 -- Architecture and Memory Page 5 of 13 greater processor s capabiity to hande 32-bit addresses. This fat memory mode provides a ogica address space range of up to 4 GB. Athough current computer hardware does not yet hande up to 4 GB of physica memory, some fie servers can now run with up to 1 GB of RAM. Virtua memory bridges the gap between physica memory and ogica memory. The 4 GB of addressabe space used as virtua memory under the fat memory mode is impemented through the use of RAM and a swap fie. The Windows 95 operating system performs memory management, caed demand paging, whereby code and data are moved in 4-KB pages between physica memory and the temporary Windows 95 swap fie on the hard drive. The Virtua Memory Manager contros paging and maintains a page tabe. The page tabe tes which pages are swapped to the hard drive, which remain in RAM, and to which system process or appication they beong. Appication programs are aocated a virtua memory address space, which is the set of addresses avaiabe for use by that program. Both 32-bit Windows and MS-DOS-based programs are aocated private virtua memory address space. A 16-bit Windows-based programs share a singe, common virtua memory address space. Figure 2.4 shows how Windows 95 aocates the 4 GB of virtua memory to each address space. Each process is aocated a unique virtua address space of 4 GB. The upper 2 GB is shared with the system, whereas the ower 2 GB is private to the appication. FIGURE 2.4 Virtua memory address space aocation. The virtua memory is aocated as foows: KB. If not used for a Virtua DOS Machine (VDM), this memory is made avaiabe for any rea-mode device drivers and terminate-and-stay-resident (TSR) programs. 0-1 MB. In a VDM, this memory is used to execute MS-DOS programs. If a shared, common, 16-bit Windows VM is used, then 16-bit Windows appications operate much as they do under Windows MB. Normay this memory is unused. Windows 95 does not use this space, nor do Windows 32-bit appications. If this memory is needed by 16-bit Windows appications, it is avaiabe. 4 MB-2 GB. This memory is used by 32-bit Windows appications and some 16-bit Windows appications. Each Windows 32-bit appication has its own address space, whereas Windows 16-bit appications a share a common address space. 2-3 GB. This memory is used to run a Core System Service components, shared DLLs, and other shared objects. Those components are avaiabe to a appications. 3-4 GB. This memory is reserved for a Ring 0 components, such as the Fie Management subsystem and the VMM subsystem. Any VxDs are oaded in this address space. Virtua memory and virtua addresses enabe you to have more memory avaiabe to programs than actuay exists on the computer in physica RAM. The Windows 95 swap fie impementation is much improved over that from Windows 3.1. With Windows 3.1, you can have either a temporary or permanent swap fie. Windows 3.1 fie://i:\chapters\z\zc676.htm 3/21/01

6 MCSE Training Guide: Windows Ch 2 -- Architecture and Memory Page 6 of 13 recommends how much hard disk memory to aocate to the swap fie. If the hard-disk controer is compatibe with 32-bit disk access, running 32-bit disk access wi improve performance. A temporary swap fie that does not need to be on contiguous hard disk space is created when Windows 3.1 starts. This same temporary swap fie is reeased when the user exits Windows. Athough a permanent, contiguous swap fie provides better performance than a temporary swap fie, because it is a static fie, hard disk space is not freed up when the user exits Windows. In Windows 95, the swap fie configuration is much easier. The best features of temporary and permanent swap fies are combined through improved virtua memory agorithms and 32-bit access methods. By defaut, Windows 95 uses a dynamic swap fie, which shrinks and grows based on the needs of the operating system and the avaiabe hard disk space. A permanent swap fie has itte benefit in Windows 95. TIP: The best way to ensure swap fie performance is to put the swap fie on a hard disk that has ampe free space so the swap fie can shrink or grow as required. If you have mutipe hard drives, seect the one with the fastest access time as we as the most free space. Windows 95 Task Scheduing and Mutitasking Windows 95 uses a task scheduer to determine the order and priority of processes running on the computer. These processes run as threads. A thread is a unit of executabe code. Each thread has a base priority, which is the priority the thread normay wants to run. MS-DOS appications and 16-bit Windows appications usuay have a singe thread. Newer 32-bit Windows appications can take advantage of running mutipe threads to improve performance. Some tasks within the 32-bit Windows appication can be spun off as separate threads that run concurrenty. Windows 95, ike Windows NT, uses priority eves to hep schedue processes. There are 32 priority eves, ranging from the owest priority eve of 0 to the highest of 31. A thread may have its base priority atered by as much as two eves higher or ower than the origina priority eve. Appications have ow priority; critica system tasks (such as I/O) have high priority. Figure 2.5 iustrates how the two parts of the scheduer process, the primary and secondary scheduer, work. The primary scheduer evauates a thread priorities and gives the thread with the highest priority a time sice of execution time. If two or more threads have the same priority, they re stacked. Each stacked thread is granted a time sice of execution in sequence unti no threads have the same priority. The actua ength of a time sice depends on the configuration of the computer. FIGURE 2.5 Scheduing threads to run. The secondary scheduer can boost the priority of non-executing threads. This priority boost heps prevent threads that have a ower base priority from being bocked from receiving execution time. The secondary scheduer aso adjusts the priority of threads over time to smooth the execution of programs. Windows 95 adjusts threads as foows: Threads waiting for user input (in the foreground) get a priority boost, making the system more responsive. fie://i:\chapters\z\zc676.htm 3/21/01

7 MCSE Training Guide: Windows Ch 2 -- Architecture and Memory Page 7 of 13 Threads competing a vountary wait get a priority boost. A threads periodicay receive a priority boost to prevent them from ocking shared resources needed by higher priority threads. Compute-bound threads get a priority decrease, so that I/O operations are not bocked. The task scheduer is the Windows 95 component responsibe for providing system resources to the appications and other processes. It aso schedues processes in a way that enabes mutipe appications to run concurrenty. This method of concurrent process scheduing is caed mutitasking. Windows 95 uses cooperative mutitasking as we as preemptive mutitasking. With Windows 3.1, appications run concurrenty using cooperative mutitasking. Cooperative mutitasking requires the appication to periodicay check the message queue and cooperativey reease contro of the system to other appications that are running. Appications that do not check the message queue reguary can "hog" CPU cyces and prevent other appications from running. For backwards compatibiity, Windows 95 cooperativey mutitasks Windows 16-bit appications. For Windows 32-bit appications, Windows 95 uses preemptive mutitasking, which aows the operating system to take contro of the processes running at any time. Preemptive mutitasking is a more efficient means of mutitasking. The task scheduer decides which processes acquire contro of the system, preemptivey aocating system resources. The priority of the process itsef is used to hep the scheduer aocate enough execution time for each process. Windows 95 Interna Messaging Windows appications use a message-passing mode to hep contro programs. An event (such as a keyboard entry, mouse movement or cick, the receipt of data by a hardware buffer, and so on) generates an interrupt. Events are converted by the interrupt hander into messages. Windows appications generate messages to request the operating system to perform a function or to pass data to another Windows appication. One botteneck for Windows 3.1 is that it uses ony a singe message queue for a appications. If ony one appication fais to retrieve its messages, the system becomes unstabe and hangs because the other appications are bocked from retrieving their messages. As a resut, the computer ocks up and you must reboot your system. This botteneck does not exist in Windows 95. Athough a singe message queue exists for a Windows 16-bit appications for backwards compatibiity (that is, for appications designed for previous versions of Windows), each Windows 32-bit appication thread has its own private message queue. Figure 2.6 iustrates this new interna messaging structure. The Windows 95 operating system takes messages from the raw input queue and passes them to the appropriate Windows 32-bit appication thread or, if the message is for a Windows 16-bit appication, to the Windows 16-bit subsystem. Therefore, if one of these processes or appications hangs and no onger receives its incoming messages, the other processes are unaffected. FIGURE 2.6 Windows 95 message-passing queue structure. fie://i:\chapters\z\zc676.htm 3/21/01

8 MCSE Training Guide: Windows Ch 2 -- Architecture and Memory Page 8 of 13 For study purposes, remember the foowing: Windows 32-bit appications have a message queue for each thread. Windows 16-bit appications share a common message queue. If a Windows 16-bit appication fais, messages are bocked for a running Windows 16-bit appications unti the faied program is ceared. MS-DOS appications do not use the message-passing design nor do they have a message queue. NOTE: Because WIN16 appications share a common memory address space and a common message queue, if a WIN16 process hangs whie in the foreground, a other WIN16 processes cease to receive messages from the operating system and appear hung. This is due to a fag that is set for WIN16 processes, known as the WIN16 mutex (Mutuay Excusive). Because 16-bit code is considered non-reentrant (it cannot be used by more than one process at a time), a system must be in pace to ensure that no two processes attempt to use the same piece of 16-bit code simutaneousy. Under Windows 95, this is done by enforcing the rue that ony the process that currenty owns the rights to the WIN16 mutex is abe to make requests to 16-bit API functions. When the given process is finished using the 16-bit code, it hands the mutex to the next process. You earn more about the mutex in Chapter 8, "Running Appications." Architectura Evauation This topic area has ony one exam objective. To propery address the objective, however, you need a cear understanding of the Windows 95 system architecture. Tabe 2.1 compares and contrasts the memory usage of a Microsoft MS-DOS-based appication, a 16- bit Windows-based appication, and a 32-bit Windows-based appication operating in Windows 95. Tabe 2.1 Comparing Memory Usage Appication MS-DOS Windows 16- bit Windows 32- bit Memory Usage Each runs in a private Virtua DOS Machine. No message queue. Loaded in the ower 1 MB of virtua memory. A run in a common address space and share a singe message queue. Loaded in the ower 2 GB of virtua memory. Each runs in a private address space, and each thread has its own message queue. Loaded in the 4 MB to 2 GB range of virtua memory. To see how Windows 95 runs appications, see Chapter 8. You aso might want to perform Exercise 2.1 to see how different appications affect the number of virtua machines that execute under Windows 95. fie://i:\chapters\z\zc676.htm 3/21/01

9 MCSE Training Guide: Windows Ch 2 -- Architecture and Memory Page 9 of 13 Exercises Exercise 2.1: Counting Virtua Machines To iustrate the point about how Windows 95 manages virtua machines, foow Exercise 2.1 to count the number of virtua machines running on your Windows 95 computer. 1. From your computer, start Windows If you instaed Windows 95 on your computer with the Typica Setup option, the System Monitor program might not be instaed, because it is an optiona component. To determine whether the System Monitor utiity program is instaed, from the Start menu, choose Programs, Access-ories, System Toos, and then System Monitor. If System Monitor is not avaiabe, you must add it to your computer by foowing these steps: a. From the Start menu, choose Settings, Contro Pane. From the Contro Pane program group, choose the Add/Remove Programs icon. b. Cick on the Windows Setup tab, doube-cick on Accessories, and add a check mark to the System Monitor check box. Press Enter or choose OK. Press Enter or choose OK again to insta the System Monitor. 3. From the Start menu, choose Programs, Accessories, System Toos, System Monitor. The System Monitor utiity program dispays key system information in either a Line Chart, Bar Chart, or Numeric Chart format. 4. Any items previousy seected are dispayed when the System Monitor utiity program starts. When you run the System Monitor utiity program for the first time, the Kerne Processor Usage (%) appears in a Line Chart. 5. You must remove a current items to run this exercise. Highight any items you want to remove, and then from the Edit menu, choose Remove Item. 6. Choose Edit, Add Item to open the Add Item diaog box. From the Category ist, cick on Kerne to dispay the ist of Kerne items. 7. Choose Virtua Machines from the Item ist. If you need an expanation of each item, choose Expain to see that this shows the number of virtua machines present in the system. Press Enter or choose OK to add the item Virtua Machines as a seection. 8. Choose View, Numeric Charts to obtain the number of virtua machines that currenty are active. Normay this vaue is 1, because the Windows 95 computer has just been started. It coud be higher. 9. Open some Windows program appications or the Windows Exporer. Has the number of virtua machines changed? The number of active virtua machines shoud not change when fie://i:\chapters\z\zc676.htm 3/21/01

10 MCSE Training Guide: Windows Ch 2 -- Architecture and Memory Page 10 of 13 Windows programs are started. 10. Start an MS-DOS command prompt by choosing Start, Run to open the Run diaog box, or choose Start, Programs, then MS-DOS Prompt. Has the number of virtua machines changed? It shoud change, because each MS-DOS appication wi start another virtua machine. 11. Start another MS-DOS command prompt, and then a third. What happens to the count of virtua machines after you start each new MS-DOS command prompt? Each time another MS- DOS command prompt is started, the number of virtua machines shoud increase by a count of 1. If the initia count was 1, then starting three MS-DOS command prompts increases the number to Cose a three MS-DOS command prompts. How many virtua machines are currenty active? The count of virtua machines shoud be back down to 1, or the starting number in step 8. Based on what you know about virtua machines, expain why the count changes during the exercise. A of the Windows 16-bit and 32-bit appications run in a singe system virtua machine. But each MS-DOS appication runs in its own Virtua DOS Machine. Opening a new MS-DOS command prompt causes the virtua machine count to increase by one. 13. When you finish viewing the System Monitor utiity information, cose the System Monitor. Review Questions The foowing questions wi test your knowedge of the information in this chapter. For additiona questions, see MCP Endeavor and the Microsoft Roadmap/Assessment Exam on the CD-ROM that accompanies this book. 1. The ring architecture of Inte 386 processes provide different eves of protection and privieges. Windows 95 executes in which two of the foowing rings of the Inte 386 protection mode? Seect the two best answers: A. Ring 0 B. Ring 1 C. Ring 2 D. Ring 3 E. Ring 4 2. Windows 95 is an advanced operating system that takes advantage of the Inte ring architecture. To understand how Windows 95 uses the ring architecture, you need to understand the rings themseves. Which one of the foowing rings of the Inte 386 protection mode offers the most privieges, incuding direct communication with the hardware components? fie://i:\chapters\z\zc676.htm 3/21/01

11 MCSE Training Guide: Windows Ch 2 -- Architecture and Memory Page 11 of 13 A. Ring 0 B. Ring 1 C. Ring 2 D. Ring 3 E. Ring 4 3. You are asked to present an overview of the Windows 95 system architecture, incuding rings. You draw a diagram that points out each ring and its protection eve. Which of the foowing rings of the Inte 386 protection mode offers no processor protection, but instead needs the operating system to provide processor protection? A. Ring 0 B. Ring 1 C. Ring 2 D. Ring 3 E. Ring 4 4. On the diagram you create for the presentation in Question 3, you need to point out where appications run. In which of the foowing rings of the Inte 386 protection mode do the MS- DOS, Windows 16-bit, and Windows 32-bit appications run? A. Ring 0 B. Ring 1 C. Ring 2 D. Ring 3 E. Ring 4 5. Within its System Services, Windows 95 uses a combination of 32-bit and 16-bit code to run appications. In which of the foowing rings of the Inte 386 protection mode do the System Services run? A. Ring 0 B. Ring 1 C. Ring 2 D. Ring 3 E. Ring 4 6. Windows 95 runs appications in Virtua Machine. The Virtua Machine Manager is used to manage these appications. In which of the foowing rings of the Inte 386 protection mode does the Virtua Machine Manager run? A. Ring 0 B. Ring 1 C. Ring 2 D. Ring 3 E. Ring 4 fie://i:\chapters\z\zc676.htm 3/21/01

12 MCSE Training Guide: Windows Ch 2 -- Architecture and Memory Page 12 of Which of the foowing components make up System Services? Seect the three best answers: A. User B. Thunk C. GDI D. GUI E. Kerne 8. John runs severa appications at once on his Windows 95 computer. Which of the foowing appications do not run in separate, private, virtua machines? A. Windows 32-bit B. Windows 16-bit C. MS-DOS D. A of the above E. None of the above 9. The Virtua Machine Manager provides severa services, incuding memory management, task scheduing, and DOS mode support. Every time you open an MS-DOS appication, the count of the number of virtua machines running under Windows 95. A. decreases by two B. decreases by one C. stays the same D. increases by one E. increases by two 10. Windows 95 uses two types of memory: physica and virtua. Virtua memory is comprised of which two of the foowing components? Seect the two best answers: A. ROM B. RAM C. VMM D. A swap fie E. A page tabe 11. For what is the 16-bit Windows mutex used? A. It protects a non-reentrant area of code from being preempted by a 16-bit process at potentiay disastrous points. B. It provides a ayer between the virtua memory space and between MS-DOS and 16- bit appications. C. It provides system resources for the appications and other processes. D. It hosts the virtua machines in which MS-DOS, Windows 16-bit, and Windows 32- bit appications run. fie://i:\chapters\z\zc676.htm 3/21/01

13 MCSE Training Guide: Windows Ch 2 -- Architecture and Memory Page 13 of 13 Review Answers 1. A D 2. A C E 3. D 4. D 5. D 6. A 7. A 8. B 9. D 10. B D 11. A fie://i:\chapters\z\zc676.htm 3/21/01