Defines OSI and its history. Describes the seven layers of the stack.
OSI means Open Systems Interconnection. It refers to the layered architecture used in computer communication design. The architecture was developed by the ISO (International Organization for Standardization). It defines the way communication is passed from one layer to another in computer systems, ultimately passing through seven different layers. The simplified representation of the OSI stack shows neighboring layers communicating with one another, through specific entities within them.
In the OSI stack the layers that interact with a human are called the higher layers. They are given the conventional levels of 5, 6 and 7. Below these are the four other layers that normally don’t interact with humans. They are called the lower layers. Normal interaction between these layers is initiated by a human from the seventh layer in one computer system, goes down to the lowest level, interfaces with another computer system, and rises up the layers of this second computer system up to the seventh, which then provides the interface with another human. A brief description of these layers follows.
The seventh layer is also known as the application layer. It operates closest to a human user. It interacts with the application that interfaces between the person and the computer system. However, the application being used directly by the user is outside the scope of the seventh OSI layer. The seventh level identifies communication partners, governs resource usage, and basically ensures quality of communication. File transfer protocols (FTP), Simple Mail Transfer Protocol (SMTP) and Telnet are examples of applications contained entirely within this layer.
The sixth layer is also called the presentation layer. It primarily determines how a computer presents its information e.g. the type of characters or file formats to use. In this way, it resolves problems that would otherwise emanate from different file encryption and origins. It then communicates with the fifth layer, also called the session layer. This layer establishes a communication session and basically organizes data into packets.
The fourth layer, called the transport layer, governs reliability and timely delivery of data to the higher layers from the lower ones. This is accomplished through data flow control, package segmentation and error control. The Transmission Control Protocol is an example of this layer. The layer is adjacent to the third one, called the network layer. The network layer provides virtual circuits which provide switching and routing for the data from one node to the next.
The second layer is also called the data link layer. In it, the logical organization of data bits transported over a medium is defined. Data gets encoded into a valid signaling format for the first layer, called the physical layer. An example of the data link layer is the HDLC (High level data link) protocol. Finally, the physical layer conveys the data stream (bits) in form of electrical impulses or radio waves at the mechanical level. Hence the cables and cards used in computer communications are part of this layer.
What is the OSI Stack
TIP-Want to start your computer within seconds?
Have you ever waited over a minute just waiting for your computer to start-up? Follow the easy steps to be able to start up or restart within SECONDS
1) Open "run" from the start menu.
2) Type "Regedit" and enter (--opens Registry Editor--)
3) This may take a few minutes but search for the folder
"HKEY_LOACAL_MECHINESYSTEMCurrentControlSetControlContentIndex"
4) After finding the folder find the Key Called "Startup Delay"
5) Double Click On It
6) A new window will come up and there will be a box named "base" with hexadecimal ticked
7) Tick Decimal
8) Its Default value Is 4800000
9) Change The value To 50000
10) Close everything including the registry editor and restart your computer.
The Five Smallest Web Design Mistakes
A list of the five smallest mistakes web designers make when building websites, and how to avoid them.
We've all come across these. They say the little things are the most important, but many web developers often overlook this obvious piece of advice. As a web developer myself, I find myself constantly looking to improve how my sites work. Could I make things easier for the user? Can I make things more robust? Does the site annoy me in anyway while I'm using it?
But we all miss things, and here's my list of the top 5 smallest mistakes websites can make.
1. Forms with amnesia
We've all had this before in one way or another, and it drives people to madness (And away from the site). You've spent 10 minutes of your time filling in a form on a website only to have your details rejected because of some mistake, but when you're sent back to the form all your precious details are gone! Even worse than this is when you added an image or video to the form and you had to wait 5 minutes for the submission to upload before it completely forgets who you are and makes you start all over again.
Real world example:
You fill out a credit application form to buy a car, but you forget to put your date of birth on it. The salesman tears the form up, and gives you a fresh one to fill out. In a fit of rage, you buy a bus pass.
Solution:
The simplest way to avoid this is to use JavaScript checking in page, so the browser will not automatically clear all the information out. If you need to use bullet-proof server-side checks, ensure you re-populate all form elements with what the user entered. If you need to upload files as part of the process, separate this onto another page to avoid annoying users.
2. Intro pages
No sane person would think that a user would want to see a picture before they are allowed to enter a website. But there is obviously a minority of people who think it's a great idea, and commit this atrocity of form over function on a regular basis. Most people don't even enter sites through the homepage anymore, Google being the main referrer or just specific links from other sites, so there ultimately an annoyance for regular visitors who have seen the intro page 10 times already. These pages serve no purpose other than to annoy people. They're the Simon Cowells of web design.
Real world example:
You go to your local cinema but are forced to stand outside the front door and watch the first 5 minutes of a movie before they let you in, even though you only wanted to buy a drink. Cinemas across the country close down as most people don't get past the front door.
Solution:
Stop doing it! If you really want to introduce people to your site with a flashy bit of design create a custom home page that maintains the general layout and function of your site, but which leaves more space for a bit of graphical showboating.
3. Disguised links
One of the things I hate about websites created by "designers", is the complete lack of attention to styles on links(hrefs). When a user is browsing a site they need to be able to pick links out of the background noise, because users tend to just skim the actual text. Removing the underscore and making links the same colour as the normal text is going to leave most links unclicked.
Real world example:
You try to go and get lunch at McDonalds, but the front doors have been disguised as a window leaving you debating which pane of glass to push. Pick the wrong one and you'll end up with a face full of glass.
Solution:
People like to find and click on links, so make them stand out! Leave them underlined until they are clicked or if you really hate those little lines, make a style that bounces out of your standard text and have a hover style.
4. Image alt tags
This is a very old problem with websites, and one which has become more important (With the introduction of WAP), then less important(With the death of WAP), then more important(Disability rights) and now it is super important! With the increase in hand held internet devices (Such as the iPhone and G1) people are looking to browse faster and on smaller screens. This means a lot of people these days are not seeing your images, and the alt tag is vital for users to navigate around your site.
Real world example:
Roads are designed with tracks in the lanes, because everyone is in a car and won't have a problem with it. Motorbike fatalities rocket overnight,
Solution:
This is a no brainer, stop being lazy and put in the tags. If you don't have the time, use an online A compliance site to test your site for compliance. Without alt tags it won't pass.
5. Flash menus
I feel stupid explaining this one; it should be as obvious as the nose on your face. Flash is a luxury, to be used sparingly and with caution. You should always assume that your users do not have it, and great pains are made to create alternate content for flash that does not load, but there is no 100% reliable method of doing this. If your intro animation
and it's alternate content does not load then that is no big loss, but if your menu is completely missing you will lose a visitor immediately. Is it really worth that just to use your favourite font?
Real world example:
You design your front door with a complicated locking system that can only be opened by people who are right-handed. Left-handed people can get in, but there not happy. People missing an arm just give you a wide berth.
Solution:
Do not use flash for your menus. Menus should be the most functional element of your site, and the easiest to use.
How to Find the Best Laptop
The crucial moment in asking the salesman to give you the best laptop that suit you. The faster, the performance is what all matter in this article.
Firstly look at the Ghz. Usually the Ghz is written in first line of the laptop specification. This is where it will determine the speed of the laptop. Remember, most of the laptop feature can be upgraded, but not this one. The Ghz thing is inside the processor. The higher it is the faster your laptop will perform. Processor with 2.5Ghz is much faster compare to 1.66Ghz.
Second, look at the RAM specification. Most of the people just ask how much is the RAM. That is a good question, but there is another important thing we have to ask; What is the maximum RAM capacity for this laptop. Mostly that I found at my place the maximum capacity is 4GB. If you can find higher, thats better for you. Usually the RAM can be upgraded when buying a laptop. So, when you are buying a laptop, ask the shop to upgrade your RAM for free. Some would give, and some would not.-smile-
Third thing is the hard drive. Usually the capacity of the hard drive doesn't matter for laptop. This is because, usually laptop are use for works, writing document, surfing the net at restaurant, shopping complex and other places.
But for the heavy user, this is the vital point in looking a laptop. Some people store musics, movies, games and many more in the hard drive. These application will need a huge hard disk. Nowadays, you could get big capacity hard disk in laptop like the 320GB and more. Anyway, there is a portable hard drive, just buy the 1TB portable hard drive. Probably, the hard drive would be enough for you for some time.
The fourth thing that is important to see, is the type of external memory card that can be read. The laptop card reader is vital for gadget user. They will need a card reader that can read M2, Memory Stick Pro Duo, Micro SD and many more that doesn't require any adapter. Usually the external memory card is stored in gadget like MP4, handphone, PSP and others.
Six Weird Computer Mice You Don't See Around Often
People are designing many different looks for the computer mouse. Here are some that may look strange, but have many other useful functions.
Keypad Mouse
Image Credit
This one is handy for number crunchers on the road: a mouse that doubles as a numerical keypad. It's better than holding down the Function Key on your laptop for a number keypad, but most people would want it in wireless. Not very ergonomically confortable either.
Cursor shaped Mouse
Here's an unusual and interesting design: a mouse shaped like a Cursor. We are assured that it is comfortable to use, it's wireless, and that it's no bigger than any other mouse. Judging by the image, we would probably think likewise.
Skype Phone Mouse
This has a handy function for Skype users: a mouse that can be used for making calls. Complete with microphone and audio control.
SpyMouse
Be careful about what you say round this mouse. It has an inbuilt condenser microphone - capable of picking up on any nearby conversations
. The website for this product even say "Exterior look and specifics are subject to change without warning", so watch out - any mouse could be a suspect.
Two Computer Mice you won't find in Shops
The Minty Box
When you have a spare optical mouse and you've got dremel tools, a minty tin, epoxy glue, a mini-hack saw, and around 4 hours of free time, this is what you get: the creative 'Minty Mouse'
Nintendo Mouse
Somebody bougght an old Nintendo Controler and installed an optical mouse inside. Result: very cool mod.
How to Find Mistakenly Deleted Files From PC/Flash Drives
Wondering how to retrieve a file you mistakenly deleted and emptied from your PC recycle bin or images and files from your digital camera, flash drives, mp3 player?
When you delete a file from your computer, it is normally moved to the recycle bin of your computer and if you empty the recycle bin then it seems you have finally cleaned the file from your computers system. Or did ever mistakenly deleted some images or files from your digital camera's flash drive or mp3 player and you wondering how you could retrieve the deleted files?
Well there are several ways out there to retrieve your deleted files, but I will like us to examine an example which is very simple and practical its a freeware windows utility by Recuva that you can actually download for free at the site www.recuva.com.
* Once installed on your computer you can actually scan for files deleted from your computers hard drive mistakenly or by bugs, crashes and viruses
* image and other files deleted from your flash drives (memory card, usb, mp3 player, external hard drives).
* The normal scan will likely give no results but if you select the advanced option and run a scan selecting the drive that you had the deleted file originally
* It will take relatively more time to complete the scan process depending on the size of the drive in question, but it certainly worth it.
* Plus it has a preview window to actually preview the files (in the case of image files) found so you can actually confirm which files you will like to recover.
* And a check box next to each file and by clicking to the check box next the specific file you will like to retrieve the recover function is activated
* Clicking the recover button gives you the option to select the location where you will like to save your recovered file and you have your deleted file again.
How to Install All the Games or Programs You Want and Not Use Up All Your Hard Drive Space
About saving space yet keeping all your games/programs installed.
How to save hard drive space while installing all the games/programs you want.
Here is my short guide of how to install all the programs you want for a minimal amount of cash and time.
Your first step is to buy a small portable hard drive that runs solely from usb power, a good example of this is Maxtor's Black Armor hard drive which is not too pricy and also has encryption as a nice extra feature. But any small usb hard drive will work.
Once you have your nice shiny new hard drive plug it in and set it up then go to my computer (just computer if you are using vista) and find your hard drive and open it up so you can see what's on it (probably nothing right now) then open up your C drive (again in my computer) and go to program files and look for programs that you don't need to run. A good example is if you have crysis (a pc game) installed and you don't want to uninstall it but you need more space for age of empires 3. Find your crysis folder and cut (ctrl+x) and then paste (ctrl+v) it onto your external hard drive. Now you have crysis on your external hard drive and enough room for age of empires. Is you want to play crysis again the cut and paste age of empires onto your hard drive and then cut and paste crysis back into program files.
Thanks for reading and I hope this all makes sense...
Make Your Computer Hour Less Frustrating
Make using the computer and the Internet more fun - Learn how to stop malfunctions and become more computer savvy.
Do you often become frustrated while you use the computer? Do you sometimes lose a lot of time dealing with a glitch or trying to learn how to do something? Every minute spent using a computer is supposed to be enjoyable. You will pick up computer tips, learn how to prevent some computer malfunctions and learn how to quickly solve some problems.
Do you sometimes have trouble logging into a web site you frequently use as a member even if you type in your correct username and password? A few months ago, I lost a lot of time trying to figure out why I could not log into one of my sites. Each time I clicked “Submit” after typing in my username and password, the landing screen said there was no match found for the username I entered. I used the site’s live helpline to no avail.
Eventually, I asked the consultant at the computer lab I was using for help. He discovered a gap between the left edge of the username field box and my username. If there is a gap between the edge of the field box and your username or password, the web site system will think you typed in an extra character. Even if you copy and paste your username or password into a field, the gap I have discussed can be created. If you incur this error, just click your mouse into the field before the beginning of your username or password and hit “Backspace”.
Do you use a flash drive to save and store documents? If you do, click the “Safely Remove Hardware” icon before unplugging your device. If you have closed out every application you have used and still receive a screen message saying your generic device cannot be unplugged, shut your computer down and then unplug your device.
Have you had it with Internet Explorer crashing and causing you to restart everything you were doing on the Internet or log back into a web site? Quit using Internet Explorer and try Mozilla Firefox, which is a safer, more convenient Internet browser service.
Whenever you cannot get a web page to load after you type in the URL for a particular web site, hit the “Refresh” button once or twice. If the page still won’t load, move on. Do not spend too much time trying to use a feature on a site. If a malfunction occurs on a site where you are a member, let the site’s customer service department know and then go to another site or do something else.
Make your passwords short and easy to remember. If you create an account on a web site but have to wait for a password to be assigned and you receive a password that is long or hard to remember in your E-mail confirmation notice, change your password to your liking once you log into your new account the first time.
Always read a site’s terms of service before filling out a form to sign up for an account. It is a hassle to fill out a form, click “Terms of Service” before you reach the “Submit” button and have to fill out the form again after you read the terms.
Reduce your time going to another site. If the site you are currently using has an extremely long link, highlight most of the link and hit “Delete” before typing in a new address.
Avoid excessive pop-up ads. Click “Tools” and activate the pop-up blocker.
Avoid tiring your arm out constantly pulling the scroll bar. Click your mouse on the screen and use the “down” arrow key to move down your page.
Do you ever use your computer speaker? To adjust the volume level, click the megaphone icon.
Speed up your Internet loading time. Use a DSL Internet service instead of a dial-up service.
Prevent glitches and power outages from destroying your work. Save your work often, especially once you finish writing a file. Hook your computer up to a surge protector.
Reduce your amount of junk mail. If unsubscribing to a particular sender does not work, click “Add to Black List”.
When you want to use a CD, make sure it is properly inserted before using it. If it does not automatically pop in, touch the middle part of the CD and push it down.
I sometimes see people spend time trying to type in a number from the ten-key pad with no results. If no number appears on the screen, hit the numeric lock key.
Follow these tips to make your computer use more enjoyable!
Mac OS X: A Web Developer's Dream
Contrary to common beliefs, Mac OS X is a very capable machine for web development.
Web developers often shy away from Mac OS X
, because they believe that it is very unsuitable in terms of web development; this is very untrue, and in this article I will talk about Mac OS X and web development, sorting out truth from fiction.
Myth #1
You can't do any real web development on Mac OS X, including server
scripts such as PHP.
The Truth
You can do the same amount of web development on Mac OS X as you can on any Windows machine; in fact, I have found Mac OS X even easier to set up server scripts. Recently I decided to set up PHP on my Mac at home to find out that Mac OS X Leopard actually comes with Apache2 and PHP5 already installed onto it! All it takes is a few configuration steps to set up PHP5 to work on your computer.
Myth #2
It is much harder to set up the use of web development languages on Mac OS X than it is on Windows.
The Truth
I have actually found it easier to set up different web development languages on my Mac than on my friends Windows computer. A few days after I set up Apache2, PHP5 and MySQL on my Mac I helped a friend do it on his Windows computer. It took at least 3 more hours to get all of them installed on his computer than on mine, and even longer to get MySQL to work because the default configuration file for MySQL on Windows does not have everything needed for it to work.
Myth #3
You might be able to do web development on Mac, but you can't get much further than the things you can do with iWeb.
The Truth
You can do the same scripting on a Mac as you can do on a Windows machine. Saying that you are confined to iWeb is like saying you are confined to Frontpage on Windows.
There are many more myths regarding Mac OS X and web development, but I think that this will help some of you realize that Mac OS X is just as good for web development as Windows is. In the end, the scripting of languages is the same on both machines because the languages do not change depending on operating systems; the only difference I can find is setting up those scripting languages, which I have found to be much easier on Mac OS X than on Windows.
