Thursday, November 29, 2007

assingment 2

virtual memory

The purpose of virtual memory is to enlarge the address space, the set of addresses a program can utilize. For example, virtual memory might contain twice as many addresses as main memory. A program using all of virtual memory, therefore, would not be able to fit in main memory all at once. Nevertheless, the computer could execute such a program by copying into main memory those portions of the program needed at any given point during execution.
1.UNIX and Windows virtual memory
Our Virtual Servers uses Unix BSDI operating systems for the majority of its servers because of the superior performance, flexibility and cost efficiency that Unix BSDI offers. The following is a comparison of the BSDI system to the Windows NT system.
With Unix and Windows NT running on standard PC's, Unix ran 27% faster than Windows NT when reading static HTML content, and with API generated content, Unix is between 47% and 197% faster. For CGI contents, Unix is 77% faster than Windows NT.
Internet Services
Unix has included things such as SMTP (Email), NNTP (News), Telnet, and DNS. All of these protocols and services were somehow forgotten by Windows NT. They can be covered up with third party products and Microsoft's own programs. However, none of these programs and products can compare to Unix in terms of flexibility and power.vv
Price Comparison
With the Unix server's cost at approximately one fourth that of the Windows NT, it allows us to provide you with a more cost effective and powerful way to be on the Internet.

Thursday, November 22, 2007

2. Two resons why a regional bank use 6 server computers than one supercomputers:
  • it can perform fastier than one supercomputer.
  • it easy to use.

Wednesday, November 21, 2007

Assignment 1

1.About 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.

Evaluation of the article:
-operating system is the main without this the program is useless cause it will not run.