How Operating Systems Work

Computer Operating Systems

When you turn on the power to a computer, the first program that runs is usually a set of instructions kept in the computer's read-only memory (ROM). This code examines the system hardware to make sure everything is functioning properly. This power-on self test(POST) checks the CPU, memory, and basic input-output systems(BIOS) for errors and stores the result in a special memory location. Once the POST has successfully completed, the software loaded in ROM (sometimes called the BIOS orfirmware) will begin to activate the computer's disk drives. In most modern computers, when the computer activates the hard disk drive, it finds the first piece of the operating system: the bootstrap loader.

The bootstrap loader is a small program that has a single function: It loads the operating system into memory and allows it to begin operation. In the most basic form, the bootstrap loader sets up the small driver programs that interface with and control the various hardware subsystems of the computer. It sets up the divisions of memory that hold the operating system, user information and applications. It establishes the data structures that will hold the myriad signals, flags and semaphores that are used to communicate within and between the subsystems and applications of the computer. Then it turns control of the computer over to the operating system.

The operating system's tasks, in the most general sense, fall into six categories:

• Processor management
• Memory management
• Device management
• Storage management
• Application interface
• User interface

While there are some who argue that an operating system should do more than these six tasks, and some operating-system vendors do build many more utility programs and auxiliary functions into their operating systems, these six tasks define the core of nearly all operating systems. Next, let's look at the tools the operating system uses to perform each of these functions.

How to install mac os x 10.7 install DVD lion on your windows pc by using virtual player or vmware workstation.

1. For installing mac os x 10.7 lion on your window pc you have to require mac os x 10.7 which you have licence version or
    you may download from torrent you have to require vmware workstation 7.1.1 which you can download from torrent or
    you may purchase lisense version of virtual matchine and pach of vmware os x lion.

2. First you have require to set up your window bios hardware virtualization enable for that you have to restart your pc and
    when boot start press esc key and select system settings and set hardware virtulization enable.

3 After that install your virtual matchine select next and select typical and select next.

4. After selecting next you want to select install latter and give next after that you give memory 200 gb and you may store
    that file select your location.

5. After selecting location and give memory size 200 GB and select want to keep in single file option and give next two times
    you can see vmware player screen with you have created virtual player.

6. After that you can select edit virtual matchine settings and open your setting and set memory 2668 MB and processors 4
    both processers 2 and hard disk size is 200 GB

7. Now in CD/DVD option you can select your mac os x 10.7 lion DVD iso file or if you have Mac OS X Lion.vmdk file if you have
    iso file then you can select that file and press ok

8. Finally power on your mac os x and you can press ctrl+G to enter in wmware matchine and press F8 for boot your iso file
    after that you can select your DVD option.

9. After that you can see apple ios is boot in your virtual matchine and now you can follow installation guide of mac os x 10.7
    lion.

10. when you install mac os x on vmware player then you can see both the screen given below.

What's new in Visual Studio 2012

It's no secret that a new age of modern apps is here. With connected devices and cloud-based services, you have bigger and better opportunities than ever before. Independent developers can plug in from anywhere, build a brilliant app, and make it available to millions of user. Large, agile teams can give their businesses a significant advantage—and the faster they execute, the greater that advantage can be.

That's why Visual Studio 2012 is one of our biggest releases yet. It comes purpose-built to help you thrive in an environment in which ideas are at a premium and speed is of the essence. Let's look at some of the ways it can help you turn ideas into applications fast.

A new look and feel

From the moment you open the IDE, you'll notice things are different. The entire interface has been redesigned to streamline workflows and provide easy access to the tools you use every day. Tool bars are simplified, tab clutter reduced, and you now have new, fast ways to find code. All of this should make it easier to navigate your application and work the way you like.

Ready for Win8

With the release of Windows 8, things have changed dramatically. Visual Studio 2012 delivers new templates, designers, and testing and debugging tools—everything you need to build addictive applications in as little time as possible. At the same time, Blend for Visual Studio gives you a visual toolkit for taking full advantage of the new (and beautiful) Windows 8 interface.

But maybe the best part of all is what you can do after you've created your application. In the old days, it wasn't always easy to get great products in front of the customers who needed them. Now you have the Windows Store, a widely available distribution channel that can reach millions of users. The terms are transparent and the potential easy to see. So you can code, sell, and maybe spend the next few years on the beach.

Web dev upgraded

When it comes to web development, Visual Studio 2012 also has you covered with new templates, better publishing tools, and full support for emerging standards, like HTML5 and CSS3, as well as the latest advances in ASP.NET. We've also made it easier to debug with the Page Inspector by interacting with the page you're coding, right in the IDE. Going mobile? With ASP.NET you can now create applications with controls that optimize for phones, tablets, and other small screens.

Cloud capable

In the old days, everyone had to maintain a server. Scaling required major investment in infrastructure. Now you have fast access to virtually unlimited servers in the cloud with the ability to add more storage and computing power on the fly. Visual Studio gives you great tools for taking your apps to Windows Azure, including new templates and publishing options, support for distributed caching, and a lower install footprint.

Up for serious business

You'll also find major improvements for SharePoint, including new designers, templates, and deployment options. You can take advantage of upgraded ALM features for SharePoint like performance profiling, unit testing, and IntelliTrace. But the pleasantest surprise of all might be LightSwitch, which enables anyone to create line of business applications without having to write a lot of code.

Flexible agile processes, solid ALM

Ok, so far we've focused mainly on development. But as applications grow more complex, you also need tools that help your team work faster and smarter. That's why we've included a flexible approach to agile. With Visual Studio and Team Foundation Server, you can adopt more productive practices at your own pace, without disrupting existing workflows. We've also invited your entire organization to the party, with new ways to track requirements and feedback from stakeholders, customers, and business team members.

You can even outsource your ALM efforts to us. With Team Foundation Service, you get ALM without the infrastructure. That way, even the smallest teams can then benefit from revision control, code reviews, and agile planning tools.

Now it's your turn

This is, of course, only a small bit of what's new in Visual Studio. You'll find plenty of more coding enhancements, ALM improvements, and tools that make your development life a little easier. (For an exhaustive list of new features,) Your task is to find out what works for you and do what you do best. Who knows? Maybe you'll write the next app that will grab everyone's attention. And that would definitely make all of our hard work worth it.

Filter in Linux

If a Linux command accepts its input from the standard input and produces its output on standard output is know as a filter. A filter performs some kind of process on the input and gives output. For e.g.. Suppose you have file called 'hotel.txt' with 100 lines data, And from 'hotel.txt' you would like to print contains from line number 20 to line number 30 and store this result to file called 'hlist' then give command:
$ tail +20 < hotel.txt | head -n30 >hlist

Here head command is filter which takes its input from tail command (tail command start selecting from line number 20 of given file i.e. hotel.txt) and passes this lines as input to head, whose output is redirected to 'hlist' file.

Consider one more following example
$ sort < sname | uniq > u_sname

Here uniq is filter which takes its input from sort command and passes this lines as input to uniq; Then uniqs output is redirected to "u_sname" file.

Pipes in Linux

A pipe is a way to connect the output of one program to the input of another program without any temporary file.

Pipe Defined as:
"A pipe is nothing but a temporary storage place where the output of one command is stored and then passed as the input for second command. Pipes are used to run more than two commands ( Multiple commands) from same command line."

Syntax:
command1 | command2

Examles: 

Command using Pipes	Meaning or Use of Pipes
$ ls | more	Output of ls command is given as input to more command So that output is printed one screen full page at a time.
$ who | sort	Output of who command is given as input to sort command So that it will print sorted list of users
$ who | sort > user_list	Same as above except output of sort is send to (redirected) user_list file
$ who | wc -l	Output of who command is given as input to wc command So that it will number of user who logon to system
$ ls -l | wc  -l	Output of ls command is given as input to wc command So that it will print number of files in current directory.
$ who | grep pratik	Output of who command is given as input to grep command So that it will print if particular user name if he is logon or nothing is printed (To see particular user is logon or not)

How to write your first Shell Script in linux?

Following steps are required to write shell script:

(1) Use any editor like vi or mcedit to write shell script.

(2) After writing shell script set execute permission for your script as follows
syntax: 
chmod permission your-script-name

Examples:
$ chmod +x your-script-name
$ chmod 755 your-script-name

Note: This will set read write execute(7) permission for owner, for group and other permission is read and execute only(5).

(3) Execute your script as
syntax: 
bash your-script-name
sh your-script-name
./your-script-name

Examples:
$ bash bar
$ sh bar
$ ./bar

NOTE In the last syntax ./ means current directory, But only . (dot) means execute given command file in current shell without starting the new copy of shell, The syntax for . (dot) command is as follows
Syntax:
. command-name

Example:
$ . foo

Now you are ready to write first shell script that will print "Knowledge is Power" on screen.

$ vi first
#
# My first shell script
#
clear
echo "Knowledge is Power"

After saving the above script, you can run the script as follows:
$ ./first

This will not run script since we have not set execute permission for our script first; to do this type command
$ chmod 755 first
$ ./first

First screen will be clear, then Knowledge is Power is printed on screen.

Script Command(s)	Meaning
$ vi first	Start vi editor
# # My first shell script #	# followed by any text is considered as comment. Comment gives more information about script, logical explanation about shell script. Syntax: # comment-text
clear	clear the screen
echo "Knowledge is Power"	To print message or value of variables on screen, we use echo command, general form of echo command is as follows syntax:  echo "Message"

Tip: For shell script file try to give file extension such as .sh, which can be easily identified by you as shell script.

Download Linux. Which linux and where?

When Linus Torvalds first developed Linux back in August of 1991, the operating system basically consisted of his kernel and some GNU tools. With the help of others Linus added more and more tools and applications.

With time, individuals, university students and companies began distributing Linux with their own choice of packages bound around Linus' kernel. This is where the concept of the "distribution" was born.

Today, creating and selling Linux distributions is a multi-million dollar business. You can buy a boxed version of Linux from companies such as Red Hat, SuSE, MandrakeSoft and others. You can also download Linux from any number of companies and individuals. There are distributions of all types and for practically any kind of computing endeavor.

For a complete list of various linux distributions and a comparison check this wiki artilce. You can follow the links there to download your favourite linux. My favourite is Cent OS.

How to use Linux?

You can use Linux as Server Os or as stand alone Os on your PC. (But it is best suited for Server.) As a server Os it provides different services/network resources to client. Server Os must be:

• Stable
• Robust
• Secure
• High Performance

Linux offers all of the above characteristics plus its Open Source and Free OS. So Linux can be used as:

(1) On stand alone workstation/PC for word processing, graphics, software development, internet, e-mail, chatting, small personal database management system etc.
(2) In network environment as:

(A) File and Print or Application Server
Share the data, Connect the expensive device like printer and share it, e-mail within the LAN/intranet etc are some of the application.

(B) Linux sever cab be connected to Internet, So that PC's on intranet can share the internet/e-mail etc. You can put your web sever that run your web site or transmit the information on the internet.

So you can use Linux for:

• Personal Work
• Web Server
• Software Development Workstation
• Workgroup Server
• In Data Center for various server activities such as FTP, Telnet, SSH, Web, Mail, Proxy, Proxy Cache Appliance etc