Tuesday, January 15, 2008

Assignment # 4

1. The major difference between deadlock, starvation and race is that in deadlock, the problem occurs when the jobs are processed. Starvation, however is the allocation of resource that prevents one job to be executed. Race occurs before the process has been started.

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
@ 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

Assignment #3

#4a.What is the cause of thrashing?
@Thrashing is caused by under allocation of the minimum number of pages required by a process, forcing it to continuously page fault.

b. How does the system detect thrashing?
The system can detect thrashing by evaluating the level of CPU utilization as compared to the level of multiprogramming.

c.Once it detects thrashing, what can the system do to eliminate this problem?
It can be eliminated by reducing the level of multiprogramming.

a.Multiprogrammng. Why is it to use?-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?
External Fragmentation happens when a dynamic memory allocation algorithm allocates some memory and a small piece is left over that cannot be effectively used. If too much external fragmentation occurs, the amount of usable memory is drastically reduced. Total memory space exists to satisfy a request, but it is not contiguous.

Sunday, December 2, 2007

Assingment No. 2

Windows Operating System;

The Windows NT Virtual Memory ManagerIn Windows NT, responsibility for managing the relationship between the virtual organization of memory (as seen by applications) with the physical organization of memory (as seen by the operating system) falls on a component of the Windows NT executive called the virtual memory (VM) manager .Memory Management GoalsWindows 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.


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

Assignment 1

1. Operating System

The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers. For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop -- it makes sure that different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system.
Operating systems can be classified as follows:
multi-user : Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users. multiprocessing : Supports running a program on more than one CPU. multitasking : Allows more than one program to run concurrently. multithreading : Allows different parts of a single program to run concurrently. real time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time. Operating systems provide a software platform on top of which other programs, called application programs, can run. The application programs must be written to run on top of a particular operating system. Your choice of operating system, therefore, determines to a great extent the applications you can run. For PCs, the most popular operating systems are DOS, OS/2, and Windows, but others are available, such as Linux.
As a user, you normally interact with the operating system through a set of commands. For example, the DOS operating system contains commands such as COPY and RENAME for copying files and changing the names of files, respectively. The commands are accepted and executed by a part of the operating system called the command processor or command line interpreter. Graphical user interfaces allow you to enter commands by pointing and clicking at objects that appear on the screen.

2. The two reasons whywe use six server computer in regional bank instead of one supercomputer
  • Because it is more usefull than the other computer
  • Because to make the work faster and no hustle