History and Components of a Modern Mainframe Computer

Mainframe computers are critical for some of the largest corporations in the world. Each mainframe has more than one modern processor, RAM ranging from a few megabytes to multiple-score gigabytes, and disk space and other storage beyond anything on a microcomputer. A mainframe can control multiple tasks and serve thousands of users every second without downtime.

The chief difference between mainframes and other computing systems is the level of processing that takes place. Mainframes are also different in terms of data bandwidth, organization, reliability, and control. Big organizations-banking, healthcare, insurance, and telecom companies, etc.-use mainframes for processing critical commercial data.

In this article, we discuss the evolution of mainframe computers and their components.

History of mainframe computers

IBM developed a critical part of mainframe computing, the Automatic Sequenced Controlled Calculator (ASCC) for arithmetic operations, in 1944. From the late 1950s through the 1970s, several companies manufactured mainframes: IBM, Burroughs, RCA, NCR, General Electric, and Sperry Rand, for example. Since then, System / 390 by IBM is the only kind of mainframe in use. It evolved from IBM's System / 360 in 1960.

An Early mainframe occupied a huge space. New technologies have drastically reduced the size and cost of the hardware. A current-generation mainframe can fit in a small closet.

Components of a modern mainframe computer

Like a PC, a mainframe has many components for processing data: operating system, motherboard or main board, processor, controllers, storage devices, and channels.

• Motherboard: The motherboard of a mainframe computer consists of a printed circuit that allows CPU, RAM, and other hardware components to function together through a concept called "Bus architecture". The motherboard has device slots for input cards and cable interfaces for various external devices. Where PC motherboards use 32- or 64-bit buses, mainframes use 128-bit buses. General instructions regarding the internal architecture help the motherboard connect to the other devices and retrieve data using binary computation.

• Processor: A CPU acts as the central processing point in mainframe architecture and includes an Arithmetic Logic Unit (ALU) for performing arithmetic calculations. It also works as a controller for the bus architecture and handles traffic and data requests. The processing power of mainframes is much higher compared to PCs, so that they can handle huge amounts of data.

• Storage devices: Storage devices are for entering, retrieving, storing, and recording data. Many are external devices, such as hard drives, tape drives, and punch card readers, all connected to terminals of the mainframe and controlled by the CPU. Their capacity for data storage can be hundred or even thousands of times that of a PC.

• Communication controllers: Communication controllers allow remote computers to access a mainframe. With the help of networks, LAN or WAN, communication controllers establish connections with various devices, perform data transmission over communication channels, and keep track of users at terminals.

• Channels: The "channels" are the cables used to connect the CPU and the main storage to other parts of the system and make sure that data is moved in a systematic way without losing its integrity.

Modern mainframes have advanced features such as expanded service management capabilities, cross-platform integration facilities, etc. And so are suitable for critical data center operations. The cost of maintaining modern mainframes is much less compared to older models.

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Website Design – Hardware and Software Tools You May Need

Before you get started with your new website or editing your current site, you need to consider which hardware and software tools you may need to support your efforts.

When it comes to hardware needed this can be very simple or reasonably complex depending on your particular needs. Of course, if you plan to create a new website (or even view your new website later) you need a computer. Simple enough, right? Not necessarily. We prefer to work with Apple Macintosh (OSX Leopard on MacBook Pro) as we do a lot of intensive graphics work and have previously invested in Adobe Creative Suite software (Photoshop, InDesign, Flash, Dreamweaver, etc.). It is just as easy to create your new website using your Windows PC but we would suggest you stay away from using Windows Vista (any version) and migrate to Windows 7 or stick with Windows XP. These operating systems are just much more stable and reliable.

Another consideration for hardware should be some sort of backup hard drive or removable USB memory stick(s). It is important that you back up all of your website data to a removable drive in the event your computer crashes, is broken or is stolen. When you create website files, most of your data will be stored on the website hosting servers but, in many cases, you will have many other “builder files” that usually never make it to the hosting servers. If you lose this data you will be forced to start from scratch in many cases. Another piece of hardware that many forget about is a HD Video Camcorder. If you plan to include video on your site, you should be investing in something half decent; you can normally pick up a good video camera that also captures “still photos” for under $500.00.

When it comes to software needed, this can be somewhat more complicated, again depending on what your website design goals are. At the very least, you will need some sort of text editing software, FTP (file transfer software), graphics creation software and then a variety of other tools as you progress.

Here are some of the most common subjects you should consider when planning the design of your website product.

COMPUTER

Do you currently have a computer that can process large files (i.e. – video files) quickly and efficiently?

WEBSITE SERVER

Are you planning to host your own website portal? If so, do you know what type of hardware and server software you will need?

BACKUP HARD DRIVE or USB STICK

Do you currently have some sort of backup hard drive equipment or plan?

VIDEO CAMERA

Will you be creating custom videos for your website and, if so, do you have a HD video camera ready to go?

MOBILE WEB DEVICES

Are you planning to make your website “mobile web friendly”? If so, do you have an iPhone and an iPad? Android phone? Blackberry device? These will be needed for testing purposes!

WEBSITE CREATION SOFTWARE

Do you have any website creation software (i.e. – Adobe Dreamweaver or Microsoft Front Page) installed, licensed and ready to use?

GRAPHICS EDITING SOFTWARE

Are you planning to create your own website graphics or edit pictures? Do you have the necessary software (i.e. – Adobe Photoshop or Photo Studio)?

DATABASES

Are you planning on creating a database for your website and, if so, do you know which software to use for this purpose?

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How to Change the MPI Node Address For a Siemens S7-300 PLC

I have seven Siemens S7-300 PLCs connected together using the MPI (Multi Point Interface) interface. The Siemens MPI protocol is used by Siemens PLCs to communicate with external devices. I want to rename each of the seven PLCs. Here are the steps to accomplish that task.

First, connect your MPI cable to the first PLC. I will be connecting my laptop to each PLC individually. Power up the PLC and open Simatic Manager. The "New Project" Wizard window will open. Just click Cancel to close the window. Now click the Accessible Nodes icon on the toolbar. A window will open showing the identification of the PLC you are connected to. My window is showing MPI = 2 (directly). Make a note of this address and close the window.

Next we need to download a hardware configuration to the PLC. This is where we will rename the PLC node address. There are probably a couple of different ways to do this – following is how I accomplish this. All seven of my PLCs are the same model; Therefore, I am using the same hardware configuration. For the obvious reasons, I want to give each a different MPI node address. I have a project file that contains all seven of my PLC programs and one hardware configuration file. I open the one hardware configuration file, and then double click Hardware in the right hand window. This will open the HW Configuration window. In this window you should see your PLC with its MPI address given.

Remember when we clicked the Accessible Nodes icon and saw MPI = 2 (directly)? My Hardware Configuration Window is showing a MPI address of 7. Place your mouse cursor on the 7 and double click. Your CPU Properties window will open. It should open to the General tab. Look down and you will see Interface Type MPI with an address of 7. Click Properties and the MPI interface Properties window will open. Using the pull down menu, choose your MPI node address and make sure the MPI (1) 187.5kbps is highlighted and click OK. You are now back on the CPU Properties window where you will see your address has changed. Click OK and you will go back to the Hard Ware window where you can verify your MPI node address has changed.

You will now click the Save and Compile icon and then click the download icon. The Select Target Module window will open. Click OK and the Select Node Address window will open. Here you will see the MPI node address you assigned earlier. You will need to click the View button right below this. You will see the current node address appear, this should be the same as what you saw earlier when you clicked the Accessible Nodes icon. Simply click on this number and you will see it appear in the MPI address slot under the Enter connection to target station. Click OK and the Download to Module window will open. Click OK and the Stop Target Modules window will open. Click OK and the "Do you want to start the module?" Window will open. Click Yes.

Now go back to the SIMATIC Manager window and click the accessible nodes icon. You will see your new MPI node address. You can see this same article with pictures at http://www.morerobototics.com .

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Understanding the Significance of Computer Hardware

We are living in an age that is highly influenced by technology. Most of the activities we need to do now are automatic or computerized. Of all the technological developments achieved in the recent past, one significant tool that got developed and which will certainly keep influencing our lives is the computer. You would agree that computers play a very basic role in our daily life, just like the television and the cell phone. We are already at a stage where life will be difficult without a computer. That makes it important to understand the way a computer works, and then be informed of what we should do if it stops working. The most important part of any computer is its hardware, in the absence of which it just can not function.

If you are really keen to assess what has gone wrong with your computer when it stops working, you should understand the working and constituents of its hardware. You should especially have solid knowledge about the computer hardware when you want to undertake its troubleshooting on your own. One important part of the hardware is the RAM memory of any computer. For running any program or application, any computer needs a RAM memory. Other than that, if the computer has a RAM with specifications that are not compatible with the programs it is expected to run, its operation will be slowed down and it would almost crawl. When choosing a computer, you need to ensure that its hardware is not outdated, otherwise you'll have to upgrade it in order to be able to use the intended program.

You must take certain basic precautions while handling the hardware of computers. The most essential precaution is to ensure that the power supply to your computer is switched off, else it could cause an electric shock. Then, before you touch any part within the computer, ensure that you are not carrying any electric charge by connecting to a grounded piece of metal or you may procure an anti-static mat or wrist band available in the market. While inspecting the hardware components, you should look for broken or damaged component, as these are most likely the reasons for the computer malfunction. If a component does not fit in the slot, you are probably trying to fit it in the incorrect slot.

Once you know the hardware employed in your computer and the role it plays in the functionality of your computer, you'll be in a position to undertake its troubleshooting when it malfunctions. Each piece of hardware contributes to the successful function of the computer. To a large extent, the working of a computer depends on the quality of its hardware, making it imperative to keep it in good condition.

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10 Top Reasons Why I Have to Upgrade My Computer

The rate at which technology is improving is very fast and in the time you get comfortable with the computer hardware you have bought, several new and improved models appear in the market. While some people prefer to keep their computers state of the art, most of us have a 'If it is not broken, do not fix it' attitude when it comes to upgrading or replacing our computers.

This is a strategy that could prove expensive in the long run. It is always better to upgrade your computer on a regular basis, especially if you have had it for over 2-3 years. Even if your computer has had a large trouble-free existence, you really need to consider periodic upgrades and here are the reasons why you must dos so:

1. Increase in Processing Speed ​​- This is one place where you really get to notice an improvement in performance. If you are upgrading from a Celeron 433MHz processor to a Pentium 4 1.6GHz, you would really notice the difference in performance!

2. Faster Memory Access – Improvements in CPU speed are typically accommodated by improvements in the speed at which data transfer occurs between the CPU and RAM. This is another area that provides an improvement in performance.

3. Size and Capacity improvements – Technology drives a reduction in component size coupled with an increase in storage capacity. This means that a RAM card or hard disk of the similar size as the older ones in your computer could have double the capacity!

4. Software Compatibility – Many of the new software packages you may wish to use in order to improve your productivity or entertainment experience may not function well on you old computer. It is better to upgrade your computer to enjoy the benefits of new software fully.

5. Obsolescence of Hardware – As your hardware gets older; Getting a replacement will get more difficult once manufacturers start phasing out the production. With improvement in technology, the older hardware becomes cheaper initially and becomes expensive as supply dries up.

6. Technical Support Issues – Many manufacturers stop providing technical support for older components as they cease production. The older your computer gets, the harder it is to find help in fixing it when it malfunctions.

7. Development of New Hardware – New hardware products appear in the market frequently that revolutionize your computer experience and are based on newly developed technology. The chances of your old computer supporting new devices are very low.

8. Faster Devices – Your old computer may not be in a position to accommodate the speed at which the new devices communicate.

9. New, Fast Communication Protocols – You may not be able to implement new or faster communication protocols in your old computer because the hardware is unable to support them.

10. Operating System and File Format – Your old hardware may not be able to run newer operating systems and some of the file formats may not be supported.

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Review of Takeoff Software for Estimating Construction

So often people want to rush out and buy estimating software or takeoff software without first trying to define their internal estimating processes. Once the estimating process is clearly defined, then and only then, can you actually try to compartmentalize the process into segments. So often the segment is really quantity takeoff. Takeoff of what you may wonder? That is like the million dollar question. This article will speak about the takeoff software process which usually associated with estimating software processes. The takeoff software process can often be takeoff of materials for some folks, and to many others, the takeoff process of scoped systems to create estimates or proposals. This review or comparison will not try to explain the estimating software process but bring to you valid quantity takeoff thinking among estimators in a quest to find which product thinks the way you do. These are the opinions of the author.

I will review and compare 3 types of measuring takeoff products:

It is extremely important to note that these are ONLY measuring takeoff programs, NOT estimating programs.

1) Planswift

2) On-Screen Takeoff by On Center Software

3) Electronic Plan Takeoff Software

All three products have their strengths, however, Planswift and On-Screen Takeoff are stand-alone products and Electronic Plan Takeoff is actually dynamically integrated live with Microsoft Excel which means that it starts and finishes and saves in Excel. They all integrate with Excel, however, you will have to evaluate your thought process and decide which of the three products work-flow think along the lines of how you think. For instance, what is the first thing you do when you get a set of plans? Typically, you start flipping through the plans to see how involved the project is and what type of work do you see that is attractive for your company. Then when you decide you are going to estimate this job, more often than not, you start like 80% of companies in the world of construction estimating by opening your takeoff master template Excel spreadsheet. You rename your spreadsheet to the new job or project and off you go performing takeoff. This is where the differences are:

In Planswift, you decide what drawing you are on and then you perform the measuring of an item you want to perform takeoff on the plan. Unfortunately, that is not exactly how an estimator thinks. Planswift does give you the ability to add a type of takeoff item on the fly by naming it and then perform takeoff of it; somewhat of a very manual and slow process. They also provide you with the ability of applying a type of assembly to a takeoff to aggregate quantities of items in that assembly. Not quite the way an estimator thinks. It forces you to jump to different screens which slows down the process. Typically, the main start of anyone’s takeoff process, or some may think of it as a checklist approach, is to start with your own spreadsheet of YOUR items. Those items can be material items or can be scoped assembly system items. Either way, by starting with a master spreadsheet say in Excel for example, many estimators think of this as a risk reducer, not to forget things they normally takeoff. Being that Planswift is a stand-alone takeoff program, it typically saves your takeoff images in Planswift instead of your estimate in Excel, if Excel is your estimating system. If you are using Excel, you have to manually save your takeoff measurement numbers in Excel and your takeoff images in Planswift or elsewhere, just not in Excel where the takeoff quantity resides. Again, if you want to integrate with Excel, they force you to either export or import takeoff items from Excel rather than being dynamically integrated live to Excel. They do however have the ability to dump the measured quantity from Planswift into any Excel spreadsheet or Word document. The main purpose or the primary focus of this program is measuring, therefore it does a good job at that function. Most of the other functions require you to jump around different screens, and essentially, you loose your thought of where you are. There are some features that attempt to address the estimating process, however, there are many features that are missing for Planswift to be a full fledged estimating system; it is NOT one. Planswift does integrate with the leading estimating system Sage Timberline, but the integration is weak. Since Timberline’s power is in assembly takeoff and where most estimators reside in Timberline, Planswift does not give the estimator the ability to add quantities of miscellaneous Timberline items or one-time items that need to added on the fly to an assembly while they are in Planswift at the Timberline interview screen, and while being in the measuring phase. Planswift does allow the deleting of assembly generated items as well adjusting assembly item quantities in a different screen. Again, to perform all that, you are forced to jump around to different screens. No assembly is ever perfect in any estimating system since project conditions are always uniquely different, therefore, having to add items to an assembly is extremely important. That adding of items and associated quantities is an absolute requirement any estimator typically has to do during the takeoff measuring and estimating phase; something that Planswift struggles with as related to Timberline Estimating. Planswift does allow the direct send of measurements to Timberline Estimating items and assemblies while in Timberline Estimating, just as you would do with the old digitizer measuring boards. Training, support and maintenance are extra for Planswift. On-Screen Takeoff by On Center Software, and Planswift charge their annual maintenance and support fees per license (mandatory) which costs the end user more expense annually especially if a customer has more than one license.

On Center’s On-Screen Takeoff is the Grand Daddy of software takeoff products due to the fact that it has been around the longest. On Center recognizes that On-Screen Takeoff is primarily a measuring program. That is why they have a separate estimating program named QuickBid for those who want an estimating program. On Center does not try to trick you into thinking it is an estimating system. In On-Screen Takeoff, you also decide what drawing you are on and then you perform the measuring of the plan. BUT, before you start, you can load a master set styles of things you typically takeoff or measure from your own library. That process seems to be less complicated than that of Planswift. On-Screen Takeoff does give you the ability to add a type of takeoff item on the fly by naming it and then performing takeoff of it; somewhat of a manual and slow process as well. The program does come with many features that are primarily focused on simple measuring to advanced measuring issues all with attention to detail regarding easy navigation for the takeoff process. On Center does a very good job at that. However, there seems to be a disconnect of thought from an Excel spreadsheet items you may use for estimating and/or proposals. The integration to Microsoft Excel is not a dynamic live link, more like an after thought in my opinion. Yes, you can establish links to named styles to cells or ranges in Excel, somewhat rigid. But the question you will have to ask yourself, which will happen more often than not is: What do you do when you need to add things on the fly during takeoff and in an Excel spreadsheet? Again there will be manual associations you will have to establish with Excel which is another major slowdown. You have to manually save your takeoff measurement numbers in Excel and your takeoff images in On-Screen or anywhere you decide, except the takeoff images will not be saved in Excel where the takeoff quantity resides. This type of situation arises when a takeoff program is a stand-alone program. On Center’s On-Screen Takeoff has the best integration with the most widely used estimating system in the USA: Sage Timberline Estimating. It basically mimics the same interview process as you would do with the old digitizer measuring boards. By working directly with Timberline, On-Screen Takeoff allows the estimator to perform takeoff of a Timberline variable question and immediately returns back directly with the takeoff quantity in a Timberline assembly at the variable question. By virtue of this process, On-Screen Takeoff allows the estimator to continue his/her Timberline interview process in Sage Timberline Estimating by reviewing/massaging generated quantities, or adding items in a Timberline assembly as the estimator see fit. That workflow process gives full control to the estimator, good job On Center. Training, support and maintenance are extra for On-Screen Takeoff. On-Screen Takeoff by On Center Software, and Planswift charge their annual maintenance and support fees per license (mandatory) which costs the end user more expense annually especially if a customer has more than one license.

This next system is ONLY if your estimating system or proposal generator is Microsoft Excel. Electronic Plan Takeoff Software is a plug-in for Excel. You start your spreadsheet, you perform the measuring takeoff, you may even add some more items on the fly all the while you are in the measuring phase in the Electronic Plan Takeoff program. When you are done, even if you added items on the fly, they automatically appear in your Excel spreadsheet. Excel is the control of everything. Your project is started in Excel, your takeoff is saved in Excel, the estimate or proposal is/can be produced there in Excel; one program, one place. Many takeoff programs interface with Excel somehow, but only Electronic Plan Takeoff is live linked with Excel, meaning all your Excel spreadsheet descriptions appear in the measuring takeoff program so you always know where you are in Excel. That is a huge difference in comparison to Planswift and On-Screen Takeoff. You can even change a description of a takeoff item in Electronic Plan Takeoff and it is automatically changed live, in your Excel spreadsheet. When you talk about the estimating and takeoff phase you must keep processes cleans and easy and this program does just that. There is no getting lost in this program. Just like the other reviewed programs above, the central focus of this program is takeoff measuring, and it does a GREAT job at that. The navigation within the program is really simple and easy. It is not made to work with other estimating systems, but there is a version that allows the direct send of measurements to any Microsoft Windows program awaiting a keyboard entry, just as you would do with digitizer measuring boards. There is also a version that works with digitizer boards as well. If you use Microsoft Excel for estimating, or takeoffs, or proposals, then this Electronic Plan Takeoff program for Excel would be your best choice. The integration to Excel is unmatched in Electronic Plan Takeoff compared to Planswift or On-Screen Takeoff. What is quite different in Electronic Plan Takeoff is that training, support, and maintenance are INCLUDED with a purchase, whereas training, support and maintenance are extra for Planswift and On-Screen Takeoff. Moreover, annual support and maintenance for Electronic Plan Takeoff year two and beyond is a low fee per company per year, instead of per license. On-Screen Takeoff by On Center Software, and Planswift charge their annual maintenance and support fees per license (mandatory) which costs the end user more expense annually especially if a customer has more than one license.

Microsoft and Excel are registered trademarks of Microsoft Corporation. Planswift is the registered trademark of Tech Unlimited, Inc. On-Screen Takeoff and QuickBid are registered trademarks of On Center Software, Inc. Sage Timberline Office, Sage Timberline Estimating are registered trademarks of Sage Software, Inc.

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Microsoft Access and Medical Private Practice

For physicians medical office software installation could be nerve-wracking, not because they want to avoid electronic medical records, but because the majority of the software packages are too complicated and very expensive for them.

The good news is, you can make your medical office software system uncomplicated and relatively easily maintained with one of the popular database software packages being used today, the Microsoft Access.

Microsoft Access is a relational database system developed by Microsoft. Microsoft Access is one of the easiest and most flexible database management solutions for the medical office and provides data validation and user-friendly features on data entry screens. It has been the dominant lightweight database system used for the last decade and has continued to grow with additional features. Access is a productive and very customizable solution for small medical practices and comes with MS Office (or standalone). However the next step up in a medical environment would be MS SQL Server but small medical offices usually only has need of a lightweight application and the added functionality with MS SQL Server, comes with a heavy price.

With this relational database system you can be up and running in one hour, which means that it is not necessary for your practice to spend lot of money to purchase, configure, update and maintain an SQL Server solution. Microsoft Access includes without any additional costs, points of integration with popular software packages including: Microsoft Word, Excel & Outlook and provides a free runtime version.

MS Access network setup is very easy. A medical office with 2-8 users is up and running within ten minutes, while installation and application maintenance is extremely simple. Virtually any user with a basic knowledge of Microsoft Access can handle all maintenance procedures without the assistance of IT personnel.

Keep also in mind that SQL Server is the flagship database system from Microsoft and it is suitable for use in environments with up to thousands of users. Microsoft Access can handle 2- 8 users and it is limited to 2 GB data storage.

We are convinced that the best way for private medical offices around the world to enter the world of electronic medical records is to purchase a professionally designed but inexpensive and affordable Microsoft Access based software solution.

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Futon Frame Maintenance and Common Replacement Parts and Hardware

A little preventative maintenance of your futon frame can greatly increase how long it lasts. We recommend checking the bolts on your futon frame every month or two, depending on how often it's used. If they are loose, gently tighten them, but be careful not to over tighten them. If you have a wooden frame, you can rub a bar of Ivory soap in the arm tracks every now and then, to keep things operating smoothly.

Most of the damage that we see is from forcing the frame to operate, when it's stuck. If you are converting your frame from a bed to a sofa, or from a sofa to a bed, and it does not easily convert, stop what you are doing, and remove the mattress, and carefully examine why it's not moving easily. Usually if you try to convert the frame and you pull on one side more than the other, something will jam, and if forced, you may break something.

Normally a guest will try to make their bed in the morning, and not knowing how to do it, they may break your frame. We suggest telling your guests to leave the futon as a bed, and you'll take care of changing it from a bed to a sofa for them.

Some parts wear out, and some of the plastic parts can dry out over the years. If the bolts are not tightened, a part can move around in a way that it's not recommended to, and that can cause it to break. People ask us why they do not make some of the parts in futon frames out of metal so they're never break. The reason is, if they were metal, and something jammed up, and was forced, the seat, or back, or an arm would crack, and that would be a more costly repair.

Here's a list of some of the more common futon frame hardware and parts. This is by no means a complete listing of all the parts, but it includes most of the common parts. Some items are called more than one name, so we list them twice. Futon store that has been around a long time, might even have obsoleste parts that you might need.

If you need a part that you can not find anywhere, consult a good futon store who's willing to help you, and give them a description and a couple of pictures showing what you need and see if they are willing to help you. They may need to know the name of the manufacturer of the frame because there are many frames that look the same, but the size of the bolts or seat decks and other items will all be slightly different.

Futon Bolts
Standard Futon Hinges
Click Click Hinges
Triple Click Hinges
Futon Mattress Storage Bags
Oblong Rollers
Carriage Blocks
Round Futon Rollers
Double Futon Rollers
Nylon Roller Inserts
Futon Barrel Nuts, Nuts, and Cross Dowels
Larger Futon Barrel Nuts
Futon Seat Stoppers
Futon Storage Bags
Allen Wrenches
Larger Allen Wrenches
Plastic Leg Caps
1/2 "Futon Hardware Sets
5/8 "Futon Hardware Sets
Angle Support Brackets
Decorative Bolt Covers or Plugs
Clevis Pins and Assemblies
Various Plastic Rollers, Glides and Carriage Blocks
Stretcher Support Rails
Futon Seat Decks
Futon Back Decks
Futon Arms
Cotter Pins
Washers and Clips
Futon Slats and Supports

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Wide Area Network (WAN)

Types and Characteristics of WANs

What is a WAN?

There are two prevailing definitions of a Wide Area Network (WAN). The book definition of a WAN is a network that spans large geographical locations, typically to interconnect multiple Local Area Networks (LANs). The practical definition of a WAN is a network that traverses a public network or commercial carrier, using one of several WAN technologies

What are its Main Components?

The main components for a WAN are routers, switches and modems. These components are described below in the hardware section.

CPE – Devices on the subscriber contracts are called customer premises equipment (CPE).
The subscriber owns the CPE or leases the CPE from the service provider. A copper or fiber cable connects the CPE to the service provider's nearest exchange or central office. This cabling is often called the local loop, or "last-mile".

DTE / DCE – Devices that put data on the local loop are called data circuit-terminating equipment, or data communications equipment (DCE). The customer devices that pass the data to the DCE are called data terminal equipment (DTE). The DCE primarily provides an interface for the DTE into the communication link on the WAN cloud.

Hardware

In a WAN you will need various types of hardware components for it to function. The typical items of hardware that you will need in a WAN are:

Router – An electronic device that connects a local area network (LAN) to a wide area network (WAN) and handles the task of routing messages between the two networks. Operates at layer 3, and makes decisions using IP addresses.

Switch – A switch is a network device that selects a path or circuit for sending a unit of data to its next destination. Operates at layer 2, and uses MAC addresses to send data to correct destination.

Modem – Short for modulator / demodulator, a modem that enables a computer to communicate with other computers over telephone lines. Operates at layer 1, where signals are converted from digital to analogue and vice versa for transmission and receiving.

Wan Standards

WANs operate within the OSI model using layer 1 and layer 2 levels. The data link layer and the physical layer. The physical layer protocols describe how to provide electrical, mechanical and functional connections to the services provided by the ISP. The data link layer defines how data is encapsulated for transmission to remote sites.

Encapsulation

Encapsulation is the wrapping of data in a particular protocol header. Remember that WANs operate at the physical layer and the data link layer of the osi model and that higher layer protocols such as IP are encapsulated when sent across the WAN link. Serial interfaces support a wide range of WAN encapsulation types, which must be manually specified. These types include SDLC, PPP, Frame delay etc. Regardless of WAN encapsulation used it must be identical on both sides of the point to point link.

Packet and Circuit Switching

Circuit switching and packet switching are both used in high-capacity networks.
The majority of switched networks today get data across the network
Through packet switching.

Circuit-switching is more reliable than packet-switching. Circuit switching is old and expensive, packet switching is more modern.

General Routing Issues

What is a Routing Protocol?

A routing protocol is a protocol that specifies how routers communicate and exchange information on a network. Each router has prior knowledge of its immediate neighbors and knows the structure of the network topology. The routers know this because the routing protocol shares this information.

Protocol

RIP (Routing Information Protocol) was one of the most commonly used protocols on internal networks. Routers use RIP to dynamically adapt changes to the network connections and communicate information about which networks routers can reach and the distance between them. RIP is sometimes said to stand for Rest in Pieces in reference to the reputation that RIP has for breaking unexpectedly and rendering a network unable to function.

Routing Algorithms

Distance Vector

This type of routing protocol requires that each router simply inform its neighbors of its routing table. The distance vector protocol is also known as the bellman-ford algorithm.

Link State

This type of routing protocol requires that each router maintain a partial map of the network. The link state algorithm is also know as Dijkstra's algorithm.

IGRP

IGRP is a type of distance vector routing protocol invented by cisco used to exchange routing data in a autonomous system. Distance vector protocols measure distances and compare routes. Routers that use distance vector must send all or a portion of their routing table in a routing update message at regular intervals to each neighbor router.

Addressing and Routing

What does routing mean?

Routing is the process of deciding how to move packets from one network to another.
The directions also known as routes can be learned by a router using a routing protocol then the information is passed from router to router along the route of the destination.

IP Address's

Every machine connected to the internet is assigned an IP address. An example of an IP address would be 192.168.0.1. IP addresses are displayed in decimal format to make it easier for humans to understand but computers communicate in binary form. The four numbers that separate an IP address are called Octets. Each position consists of eight bits. When added to together you get 32 ​​bit address. The purpose of each octet in an IP address is to create classes of IP addresses that can be assigned within a network. There are three main classes that we deal with Class A, B and C. The octets of an IP address are split into two parts Network and Host. In a class A address the first octet is the network portion, this determinates which network the computer belongs to, the last octets of the address are the hosts that belong to the network.

Sub netting

Sub netting allows you to create multiple networks within a class A, B or C address. The subnet address is the address used by your LAN. In a Class C network address you would have a subnet mask of 255.255.255.0. A subnet mask identifies which portion is network and which is host. For example 192.168.6.15 the first octet three octets are the Network address and the last octet being the host (Workstation). It is important to subnet a network because gateways need to forward packets to other LANS. By giving each NIC on the gateway an IP address and a Subnet mask it allows the gateways to route packets from LAN to LAN. Once the packet arrives at its destination, the gateway then uses the bits of the subnet portion of the IP address to decide which LAN to send the packets.

Circuit Switched Leased Lines

A circuit switched network is one that establishes a dedicated circuit (or channel) between nodes and terminals before the users may communicate. Here are some terminologies associated with a Circuit switched network.

Frame relay is a telecommunication service designed for cost-efficient data transmission between local area networks (LANs)

Basic rate interference is a service used by small business for internet connectivity. An ISDN BRI provides two 64 Kbps digital channels to the user.
Primary rate interface (PRI) is a telecommunications standard for carrying voice and data transmissions between two locations
All data and voice channels are ISDN and operate at 64kbit / s

Packet Switching

Http://www.raduniversity.com/networks/2004/PacketSwitching/main.htm – _Toc80455261

Packet switching refers to protocols in which messages are broken up into small packets before they are sent. Each packet is then transmitted over the Internet. At the destination the packages are reassembled into the original message. Packet switching main difference from Circuit Switching is that that the communication lines are not dedicated to passing messages from the source to the destination. In Packet Switching, different messages can use the same network resources within the same time period.

Http://en.wikipedia.org/wiki/Asynchronous_Transfer_Mode

Asynchronous Transfer Mode (ATM) is a cell relay, packet switching network and protocolwhich encodes data into small fixed-sized cells.

ISDN is used to carry voice, data, video and images across a telephone network. ISDN stands for integrated services Digital Network. Isdn also provides users with a 128kbps bandwidth. This is done through frame relay. Frame relay complements and provides a service between ISDN, which offers bandwidth at 128 Kbps and Asynchronous Transfer Mode which operates in somewhat similar fashion to frame relay but at speeds from 155.520 Mbps or 622.080 Mbps. Frame relay is based on the older X.25 packet switching technology and is used to transmit analogue signals such as telephone conversations.

PSDN stands for packet switched data network and is a data communication network. Packet switched networks do not establish a physical communication signal like the public telephone circuit (circuit switched network) Packets are sent on a fixed length basis and assigned with a source and a destination address. The packages then explicitly on the routers to read the address and route the packets through the network.

Mobile and Broadband Services

Digital Subscriber Line (DSL) is mainly used to bring high bandwidth connections to homes and small business's over a copper wire telephone line. This is can only be achieved if you stay within the range of the telephone exchange. DSL offers download rates of up to 6mbps allowing continuous transmission of video, audio and 3D effects. DSL is set to replace ISDN and compete with the cable modem in providing multimedia to homes. DSL works by connecting your telephone line to the telephone office over copper wires that are twisted together.

Asymmetric Digital Subscribers Line is most commonly used for home users. It provides a high download speed but a lower upload speed. Using ADSL, up to 6.1 megabits per second of data can be sent downstream and up to 640 Kbps upstream.

Http://en.wikipedia.org/wiki/Symmetric_Digital_Subscriber_Line

Symmetric Digital Subscriber Line is a digital subcriber line which runs over one pair of copper wires. The main difference between ADSL and SDSL is the difference in upload and download speeds. SDSL allows the same upstream data rate and downstream data rate as ADSL upstream can be very slow.

[Http://searchnetworking.techtarget.com/sDefinition/0],,sid7_gci558545,00.html

HDSL High bit-rate Digital Subscriber Line, one of the earliest forms of DSL, is used for wideband digital transmission within a corporate site and between the telephone company and a customer. The main characteristic of HDSL is that that provides equal bandwidth in both directions.

IDSL is a system in which data is transmitted at 128 Kbps on a regular copper telephone line from a user to a destination using digital transmission.

The Local Loop enables operators to connect directly to the consumer via copper local loops and then add their own equipment to offer broadband and other services. This process involves operators accessing local exchange buildings to connect to a network of copper lines which connect them to homes and businesses. BT is an Example of a Local Exchange. The local loop connecting the telephone exchange to most subscribers is capable of carrying frequencies well beyond the 3.4 kHz upper limit.

Benefits of using DSL

DSL can provide a virtual instantaneous transmission of voice, data and video over ordinary copper phone lines. A DSL connection can eliminate delays while waiting to download information and graphics from the Internet. It provides users with a cost effective high speed Internet connection. Another benefit is that a DSL connection is always on-line (like a LAN connection) with no waiting time for dialing or connecting.

There are now more than 10 million broadband connections in the UK. By December 2005 there were 9.792 million broadband connections in the UK and the average broadband take up rate during the three months to December was more than 70,000 per week.

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Computer Engineer Salary

A report by CNNmoney states that students who majored in computer engineering were the top earners of the class of 2011. On top of that according to the Bureau of Labor Statistics, the demand for computer software engineers is expected to grow by nearly 38% by 2016 You may have just stumbled upon your new career!

There are two types of engineers, hardware and software. A hardware engineer deals with physical components. They research, design, and test the physical components of a computer including circuit boards, chips, and keyboards. A software engineer, called developers, create programs for users to perform task. They create the software that translates the commands from applications into instructions that the hardware can understand. They create the operating systems and computer interfaces for desks and consumer electronics.

95% of jobs are located in metropolitan areas. Positions are located in research labs and manufacturing labs. Some work in computer system design firms, research and develop firms, or federal government. Just as there is a range of potential work environments you may end up being in, there are also a large variety of things you may be creating programs for. Computer engineers create on computers, cell phones, navigational systems in your car, video games, and etc. If you're creative, love computers, and do not mind making a lot of money in the process then this just might be for you!

Some of the highest income makers coming directly out of college are graduates in the computer engineering field. This is a great incentive to buckled down and stay focused on those late nights studying in your dorm. This will literally pay off .. BIG TIME! The average salary for computer engineer job postings nationwide are 29% higher than average salaries for all jobs nationwide. Sound good yet? Let's get into the specifics.

The overall computer engineer salary is $ 87,000. To be even more specific let's discuss what you can expect if you enter involved in hardware or software. Starting with the low end of what you can expect. As a software engineer the lowest 10% average $ 45.44 / hr or $ 57,810 annually. The highest 10% average $ 65.28 or $ 135,780. As a hardware engineer the percentages or a slight bit higher. A hardware computer engineer salary on the low end can on average expect $ 48.73 / hr or $ 62,400. The highest 10% of hardware engineers make $ 70.07 / hr or $ 147,610. Not a bad day's work!

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