Tuesday, January 15, 2008
2. Example of Deadlock: When two person are about to buy one product at the time.
Example of Starvation: When one person borrowed a pen from his classmate and his
classmate get his pen back.
Example of Race: When two guys have the same girlfriend.
3. Four necessary condition needed for the deadlock from exercise #2:
if the product is only one.
if the two person needed that one product urgently.
if there's other alternative products available.
if the two person are brand concious and the product happen to be what they like.
a. Deadlock will not happen because there are two traffic lights that control the traffic. But when some motorist don't follow the traffic lights, deadlock can occur because there's only one bridge to drive through.
b. Deadlock can be detected when there will be a huge bumper to bumper to the traffic and there will be accident that will happen.
c. The solution to prevent deadlock is that, the traffic lights should be accurate and motorist should follow it. In order to have a nice driving through the bridge.
Thursday, December 13, 2007
- page 104 question # 4
What is the cause of thrashing? How does the system detect thrashing? Once it detects thrashing, what can the system do to eliminate this problem?
a. The thrashing is caused by mainly by the file indexing in vista and not with your page file. Indexing usually happens in the first 15mins after you boot up - its normal.Your pagefile seems very large - try to make it a fixed size of about 1024Mb on a second HD if possible. Have you inserted a spare USB memory stick for readyboost - it helps reduce thrashing later on.
Thrashing is caused by under allocation of the minimum number of pages required by a process, forcing it to continuously page fault. The system can detect thrashing by evaluating the level of CPU utilization as compared to the level of multiprogramming. It can be eliminated by reducing the level of multiprogramming.
b. How does the operating sytem detect thrashing?
-An operating system would have no idea that thrashing is happening. The OS would be responsible for making use of virtual memory to make up for the lack of physical RAM during a particular computing session, but would have no concept that this is causing issues with hardware.
c. Once thrashing is detected, what can the operating system do to eliminate it?
-Thrashing is usually a symptom of low memory in your system. To minimize it, try adding more memory to your computer or try to cut down on use interface elements that use extra memory like complicated background images and detailed icons.
- pg. 56 question # 1-3
a.) Multi programming:
-Multiprogramming is the technique of running several programs at a time using timesharing. It allows a computer to do several things at the same time. Multiprogramming creates logical parallelism. The concept of multiprogramming is that the operating system keeps several jobs in memory simultaneously. The operating system selects a job from the job pool and starts executing a job, when that job needs to wait for any i/o operations the CPU is switched to another job. So the main idea here is that the CPU is never idle.
b.)Internal fragmentation. How does it occur?
-Internal fragmentation is the space wasted inside of allocated memory blocks because of restriction on the allowed sizes of allocated blocks. Allocated memory may be slightly larger than requested memory; this size difference is memory internal to a partition, but not being used.
c.) External fragmentation. How does it occur?
-the external fragmentation is to create a minimum swap file size that somewhat exceeds the usual size of your swap file. If your swap file exceeds the minimum, external fragmentation will occur. Setting a maximum that may be exceed is ill advised as it can crash your system if it is exceeded.
d.) Compaction. Why is it needed?
e.) Relocation. How often should it be performed?
- Relocation is the process of replacing symbolic references or names of libraries with actual usable addresses in memory before running a program. It is typically done by the linker during compilation, although it can be done at run-time by a loader. Compilers or assemblers typically generate the executable with zero as the lower-most, starting address. Before the execution of object code, these addresses should be adjusted so that they denote the correct runtime addresses.
2. Describe the major disadvantages for each of the four memory allocation schemes presented in the chapter?
- The major disadvantage only 1 job per partition and waste of main storage.
3. Describe the major advantages for each of the memory allocation schemes presented in the chapter?
-The major advantage of this is operating system is easy to implement.
Thursday, November 29, 2007
- Windows operating sysyem
Windows NT is a portable, secure, multithreaded, multiprocessing operating system. As a result, its virtual memory manager must:• Be compatible with multiple processor types • Protect the NT Executive from applications • Protect applications from each other • Provide mechanisms for programs to efficiently share physical memory (RAM). • Be efficientAn Application's View of MemoryIn Windows NT, applications access memory using a 32-bit linear addressing scheme. This scheme is sometimes referred to as flat memory model because applications view memory as one linear (or flat) array of memory locations. Applications address memory using simple 32-bit offsets from address zero (0). Since a 32-bit offset can specify 232 memory addresses, each application can access up to 4 Gb of (virtual) memory. The range of addresses an application can access is called the application's address space (Figure 7).The 32-bit flat memory model makes Windows NT portable because it is compatible with the memory addressing of processors such as the MIPS R4000 and DEC Alpha. It also simplifies porting of applications originally written for flat memory model environments such as Unix and the Apple Macintosh.The flat memory model used in Windows NT contrasts sharply with the segmented model used in Windows for MS-DOS. In Windows for MS-DOS, memory is broken into many differently sized segments, each with a maximum length of 64K. This has been a major difficulty for developers of Windows applications for a very long time because changing segments is somewhat difficult and slow. This difficulty has led to many 64K limits in a lot of software, including the Windows 3.1 resource heap. The 32-bit flat memory model does away with all of these constraints.
- UNIX OPERATING SYSTEM
Most corporations have UNIX systems for handling heavy-duty applications. Microsoft Windows 2000 has been rapidly gaining ground because it provides better performance at lower cost. But companies aren't going to replace UNIX with Windows 2000—they've invested too much in their UNIX systems over the years. So many companies are choosing to add Windows 2000 to support departmental functions. It's expensive and inefficient to run two separate systems side by side so network and IT managers need to learn how to integrate Windows 2000 with their existing UNIX systems. This book shows them how to do just that and much more. The expert authors of this book approach Windows 2000 from a UNIX Systems administrator's point of view.
Wednesday, November 21, 2007
Operating systemFrom Wikipedia, the free encyclopediaJump to: navigation, searchAn operating system (OS) is the software that manages the sharing of the resources of a computer and provides programmers with an interface used to access those resources. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the system. At the foundation of all system software, an operating system performs basic tasks such as controlling and allocating memory, prioritizing system requests, controlling input and output devices, facilitating networking and managing file systems. Most operating systems come with an application that provides a user interface for managing the operating system, such as a command line interpreter or graphical user interface. The operating system forms a platform for other system software and for application software.
The most commonly-used contemporary desktop OS is Microsoft Windows, with Mac OS X also being well-known. Linux and the BSD are popular Unix-like systems.
2) the two reason why we use six server computer in regional bank instead of one super computer
- the first reason is that why we use six server computer in regional bank instead of one super computer is because so that we can easily work faster ,and it is faster to finish
- the second reason is that why we use six server computer in regional bank instead of one super computer is that the computer will have more faster reading in a program and so that the search that you've looking for can be easily found because of the help of the six server computer .