Networking Part 1

Let us start with our New topic on Networking.

Basics of Networking

When looking at networking basics, understanding the way a network operates is the first step to understanding routing and switching. The network operates by connecting computers and peripherals using two pieces of equipment; switches and routers. Switches and routers, essential networking basics, enable the devices that are connected to your network to communicate with each other, as well as with other networks.

Though they look quite similar, routers and switches perform very different functions in a network.

Networking Basics: Switches

    Switches are used to connect multiple devices on the same network within a building or campus. For example, a switch can connect your computers, printers and servers, creating a network of shared resources. The switch, one aspect of your networking basics, would serve as a controller, allowing the various devices to share information and talk to each other. Through information sharing and resource allocation, switches save you money and increase productivity.

    There are two basic types of switches to choose from as part of your networking basics: managed and unmanaged.
        An unmanaged switch works out of the box and does not allow you to make changes. Home-networking equipment typically offers unmanaged switches.
        A managed switch allows you access to program it. This provides greater flexibility to your networking basics because the switch can be monitored and adjusted locally or remotely to give you control over network traffic, and who has access to your network.

Networking Basics: Routers

    Routers, the second valuable component of your networking basics, are used to tie multiple networks together. For example, you would use a router to connect your networked computers to the Internet and thereby share an Internet connection among many users. The router will act as a dispatcher, choosing the best route for your information to travel so that you receive it quickly.

    Routers analyze the data being sent over a network, change how it is packaged, and send it to another network, or over a different type of network. They connect your business to the outside world, protect your information from security threats, and can even decide which computers get priority over others.

    Depending on your business and your networking plans, you can choose from routers that include different capabilities. These can include networking basics such as:
        Firewall: Specialized software that examines incoming data and protects your business network against attacks
        Virtual Private Network (VPN): A way to allow remote employees to safely access your network remotely
        IP Phone network : Combine your company's computer and telephone network, using voice and conferencing technology, to simplify and unify your communications

OPERATING SYSTEM

What is an Operating System ?

The operating system is 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.

 An operating system (sometimes abbreviated as "OS") is the program that, after being initially loaded into the computer by a boot program, manages all the other programs in a computer. The other programs are called applications or application programs. The application programs make use of the operating system by making requests for services through a defined application program interface (API). In addition, users can interact directly with the operating system through a user interface such as a command language or a graphical user interface (GUI).

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.

An operating system performs these services for applications:

    In a multitasking operating system where multiple programs can be running at the same time, the operating system determines which applications should run in what order and how much time should be allowed for each application before giving another application a turn.
    It manages the sharing of internal memory among multiple applications.
    It handles input and output to and from attached hardware devices, such as hard disks, printers, and dial-up ports.
    It sends messages to each application or interactive user (or to a system operator) about the status of operation and any errors that may have occurred.
    It can offload the management of what are called batch jobs (for example, printing) so that the initiating application is freed from this work.
    On computers that can provide parallel processing, an operating system can manage how to divide the program so that it runs on more than one processor at a time.

All major computer platforms (hardware and software) require and sometimes include an operating system. Linux, Windows, VMS, OS/400, AIX, and z/OS are all examples of operating systems.


Types of operating systems

Operating systems usually come preloaded on any computer you buy. Most people use the operating system that comes with their computer, but it's possible to upgrade or even change operating systems.

The three most common operating systems for personal computers are Microsoft Windows, Apple Mac OS X, and Linux.

Modern operating systems use a graphical user interface, or GUI (pronounced gooey). A GUI lets you use your mouse to click icons, buttons, and menus, and everything is clearly displayed on the screen using a combination of graphics and text.

Each operating system's GUI has a different look and feel, so if you switch to a different operating system it may seem unfamiliar at first. However, modern operating systems are designed to be easy to use, and most of the basic principles are the same.

Thermodynamics

Thermodynamics

Thermodynamics is a branch of physics concerned with heat and temperature and their relation to energy and work. It defines macroscopic variables, such as internal energy, entropy, and pressure, that partly describe a body of matter or radiation. It states that the behavior of those variables is subject to general constraints, that are common to all materials, not the peculiar properties of particular materials. These general constraints are expressed in the four laws of thermodynamics. Thermodynamics describes the bulk behavior of the body, not the microscopic behaviors of the very large numbers of its microscopic constituents, such as molecules. Its laws are explained by statistical mechanics, in terms of the microscopic constituents.

It was born in the 19th century as scientists were first discovering how to build and operate steam engines. Thermodynamics deals only with the large scale response of a system which we can observe and measure in experiments. Small scale gas interactions are described by the kinetic theory of gases. The methods complement each other; some principles are more easily understood in terms of thermodynamics and some principles are more easily explained by kinetic theory.

Laws Of Thermodynamics

The four laws of thermodynamics define fundamental physical quantities (temperature, energy, and entropy) that characterize thermodynamic systems. The laws describe how these quantities behave under various circumstances, and forbid certain phenomena (such as perpetual motion).

The four laws of thermodynamics are:

    Zeroth law of thermodynamics: If two systems are in thermal equilibrium respectively with a third system, they must be in thermal equilibrium with each other. This law helps define the notion of temperature.

    First law of thermodynamics: When energy passes, as work, as heat, or with matter, into or out from a system, its internal energy changes in accord with the law of conservation of energy. Equivalently, perpetual motion machines of the first kind are impossible.

    Second law of thermodynamics: In a natural thermodynamic process, the sum of the entropies of the participating thermodynamic systems increases. Equivalently, perpetual motion machines of the second kind are impossible.

    Third law of thermodynamics: The entropy of a system approaches a constant value as the temperature approaches absolute zero. With the exception of glasses the entropy of a system at absolute zero is typically close to zero, and is equal to the log of the multiplicity of the quantum ground state.

There have been suggestions of additional laws, but none of them achieve the generality of the four accepted laws, and they are not mentioned in standard textbooks.

The laws of thermodynamics are important fundamental laws in physics and they are applicable in other natural science.