What is Computer Graphics?

The term computer graphics includes almost everything on computers that is not text or sound. Today almost every computer can do some graphics, and people have even come to expect to control their computer through icons and pictures rather than just by typing.Here in our lab at the Program of Computer Graphics, we think of computer graphics as drawing pictures on computers, also called rendering. The pictures can be photographs, drawings, movies, or simulations -- pictures of things which do not yet exist and maybe could never exist. Or they may be pictures from places we cannot see directly, such as medical images from inside your body.We spend much of our time improving the way computer pictures can simulate real world scenes. We want images on computers to not just look more realistic, but also to BE more realistic in their colors, the way objects and rooms are lighted, and the way different materials appear. We call this work "realistic image synthesis", and the following series of pictures will show some of our techniques in stages from very simple pictures through very realistic ones.

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Statements in QBASIC

Statements in QBASIC

A statement (for the QBASIC) is a set of instructions written by using keywords or commands of QBASIC. Every programming language uses keywords as a statement with certain syntax. The keywords have specific meaning in the QBASIC programming. The statements are the first stored in the memory and executed only when the RUN command is given.

Different statements used in QBASIC are as follows:
CLS Statement

The CLS statement clears the screen. If you write CLS statement in the middle of the program then you cannot see the outputs generated before execution of CLS because it clears the screen.
Syntax: CLS

LET Statement

LET is an assignment statement. It is used to assign the value to a variable. LET is an optional statement i.e. without using LET statement one can assign the value to a variable. The data type must match with the variable type otherwise type mismatch error will occur.

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THE FIVE TYPES OF COMPUTERS

   TYPES OF COMPUTERS
* Mainframe  
-      first type of computer used by government and businesses
-      multiple tasks for many users simultaneously
-      Large corporations
-      Climate controlled rooms
-      Hook-up to it through personal computer
-      Examples  government agencies accessing social security numbers/info
-      National car rental company access info on anytime/where you have ever rented a car
-      Credit card companies customer service

* Supercomputer
-       Processes trillions of calculations per second
-       Weather forecasting
-       Crash testing
-       Special effects in movies
-       $100 million
-       Why do people spend this much on a computer? save lives or will make more than it cost

* Minicomputers
-        Popular in the 70 and 80
-        Small to medium size companies
-        Schools and small office companies (less than 100 people)
-        Less than $100,000
-       Now that PCs are so powerful, these are becoming OBSO.

* Personal Computers
-        Exploded in the early 80
-        Cost is always decreasing
-        Use to have a lot of types now Apple and IBM  compatible (Apple good for media)
-        Rapid processing and relatively low cost
-        Scientist, graphics, financial analyst, architects
-        $2000-$9000

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  Alternately referred to as a processor, central processor, or microprocessor, the CPU (pronounced sea-pea-you) is the Central Processing Unit of the computer. A computer's CPU handles all instructions it receives from hardware and software running on the computer.As you can see in the above picture, the CPU chip is usually in the shape of a square or rectangle and has one notched corner to help place the chip properly into the CPU socket. On the bottom of the chip are hundreds of connector pins that plug into each of the corresponding holes in the socket. Today, most CPU's resemble the picture shown above. However, Intel and AMD have also experimented with slot processors that were much larger and slid into a slot on the motherboard. Also, over the years, there have been dozens of different types of sockets on motherboards. Each socket only supports specific types of processors and each has its own pin layout.

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Features of External Hardware Computer Components

External computer components connect to a computer system from OUTSIDE. They are not necessary for the system to function but make our experiences easier or better. We will discuss the following:

* Input Devices (used to get data into a computer)
*Output Devices (used to get information out of a computer)

* Peripherals

    Input Devices
        Input devices are pieces of hardware that get raw data into the computer ready for processing.
        Processing involves taking raw data and turning it into more useful information.

        Input devices fall into two categories:

     *  Manual Input Devices - Need to be operated by a human to input information
     * Automatic Input Devices - Can input information on their own.

   * Output Devices

    When inputted raw data has been processed it becomes usable information. Output devices are        pieces of hardware that send this usable information out of the computer.

   Some output devices send information out temporarily and some send information out permanently:

  * Temporary Output Devices 
  * Permanent Output Devices

  *Peripheral Devices

   Almost all input and output devices are known as 'Peripheral devices'. 
   These are 'non-essential' hardware components that usually connect to the system externally.
   Peripherals are called non-essential because the system can operate without them.

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Where is the CPU located on the motherboard?

CPU/processor. The central processing unit (CPU), also called a processor, is located inside the computer case on the motherboard. It is sometimes called the brain of the computer, and its job is to carry out commands.

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High level languages

A programming language such as C, FORTRAN, or Pascal that enables a programmer to write programs that are more or less independent of a particular type of computer. Such languages are considered high-level because they are closer to human languages and further from machine languages. In contrast, assembly languages are considered low-level because they are very close to machine languages.

               The main advantage of high-level languages over low-level languages is that they are easier to read, write, and maintain. Ultimately, programs written in a high-level language must be translated into machine language by a compiler or interpreter.The first high-level programming languages were designed in the 1950s. Now there are dozens of different languages, including Ada, Algol, BASIC, COBOL, C, C++, FORTRAN, LISP, Pascal, and Prolog.

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How to Burn a DVD From a computer?

 Burn a DVD From a computer

           Burning a video to a DVD is one of the primary reasons for owning a laptop with a DVD burner. The task can be intimidating for first-time users, but various DVD burning software can make the task a lot less daunting. Most laptops that have a built-in DVD burner will also come with software to assist in the task of creating DVDs. However, since the majority of laptops run on the Windows operating system, this article will focus on using Windows DVD Maker to create a DVD.

         Locate Windows DVD Maker software from your start menu, under 'All Programs.'

         Windows DVD Maker opening screenshot Click on the options link and select the options that you want for your DVD. Here is where you can decide what menu options you want for the DVD as well as the aspect ratio and format. The defaults are fine for most productions.

           Windows DVD Maker options menu screenshot

Click on 'Add Items' from the menu bar to select pictures and video for your DVD. You will notice a running time total in the left hand bottom of this window. The total alloted time for a DVD is 150 minutes using this method.

 Selecting DVD content

      
             Click to move to the next screen, where you will see that you are now ready to burn the files to a DVD. It is here that you can preview your DVD, make your menu selections add music to your slide show and even customize the menu if that is what you decide.

            Windows DVD Maker menu options

Insert a blank DVD R/RW disk into the DVD R/RW drive. Click on the 'Burn' button from the final window left once you completed step four. If you do not already have a disk in the laptop's DVD drive, it will instruct you to put one in. Once the program completes the burn of video to the DVD, it will notify you that it is complete and eject the DVD.

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Define function of the monitor of the computer?

Define function of the monitor of the computer

                A computer monitor is a display adapter that displays information processed by the computer's video card. When a video card or graphics card converts binary information from is and 0S into images, these images are displayed onto the directly connected monitor. There are different types of monitors, including cathode ray tube (CRT) and liquid crystal displays (LCD). Monitors have display functions that include powering it on and off, controlling brightness, contrast and position, among others.

LCD

                A liquid crystal displays or LCD is a type of flat panel monitor, meaning it's designed to be thin. This feature should not be confused with flat screen, meaning the computer monitor's screen is flat instead of curved. LCD refresh their screen differently than CRT monitors. An LCD screen is created by electric voltages hitting liquid crystal cells, allowing 64 different shades per cell. LCD have one resolution size, and, if a smaller resolution is adopted, a black border will appear around the re-sized resolution.

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Useful programs

Useful programs

         Here are some computer programs useful in understanding and implementing dissonance-based tuning and timbres. Since I usually program in the language MATLAB, most of these are MATLAB programs, although the dissonance calculating program is also available in Microsoft's version of BASIC. Morgan Thunder has also translated the dissonance measuring program into C, and updated by Prof. Frink while Mauricio Rodriguez has translated it into LISP -- thanks Morgan, Prof. Frink, and Mauricio!

       To calculate the dissonance of a sound with a given spectrum, use the following program, which should be placed in your MATLAB folder and called dismeasure.
The logical structure and the meaning of the variables are discussed in the section How to Calculate Dissonance Curves of the paper Relating Tuning and Timbre, which is available on-line for your browsing pleasure.

      A pair of useful MATLAB programs converts from musical ratios into cents, and back again. The which should be named ratcent and centrat and placed in your MATLAB folder. As usual in MATLAB the input variables cents and ratios can be scalars or vector.

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Different between hardware and software?

The beauty of a computer is that it can run a word-processing program one minute and then a photo-editing program five seconds later. In other words, although we don't really think of it this way, the computer can be reprogrammed as many times as you like. This is why programs are also called software. They're "soft" in the sense that they are not fixed: they can be changed easily. By contrast, a computer's hardware the bits and pieces from which it is made and the peripherals, like the mouse and printer, you plug into it is pretty much fixed when you buy it off the shelf. The hardware is what makes your computer powerful; the ability to run different software is what makes it flexible. That computers can do so many different jobs is what makes them so useful and that's why millions of us can no longer live without them.

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What do you mean by operating system?

Suppose you're back in the late 1970, before off-the-shelf computer programs have really been invented. You want to program your computer to work as a word processor so you can bash out your first novel—which is relatively easy but will take you a few days of work. A few weeks later, you tire of writing things and decide to reprogram your machine so it'll play chess. Later still, you decide to program it to store your photo collection. Every one of these programs does different things, but they also do quite a lot of similar things too. For example, they all need to be able to read the keys pressed down on the keyboard, store things in memory and retrieve them, and display characters (or pictures) on the screen. If you were writing lots of different programs, you'd find yourself writing the same bits of programming to do these same basic operations every time. That's a bit of a programming chore, so why not simply collect together all the bits of program that do these basic functions and reuse them each time.

A typical computer architecture linking the hardware to the applications via the BIOS and the operating system.

That's the basic idea behind an operating system: it's the core software in a computer that (essentially) controls the basic chores of input, output, storage, and processing. You can think of an operating system as the "foundations" of the software in a computer that other programs (called applications) are built on top of. So a word processor and a chess game are two different applications that both rely on the operating system to carry out their basic input, output, and so on. The operating system relies on an even more fundamental piece of programming called the BIOS (Basic Input Output System), which is the link between the operating system software and the hardware. Unlike the operating system, which is the same from one computer to another, the BIOS does vary from machine to machine according to the precise hardware configuration and is usually written by the hardware manufacturer. The BIOS is not, strictly speaking, software: it's a program semi-permanently stored into one of the computer's main chips, so it's known as firmware, it is usually designed so it can be updated occasionally, however.

Photo: Typical computer architecture: You can think of a computer as a series of layers, with the hardware at the bottom, the BIOS connecting the hardware to the operating system, and the applications you actually use (such as word processors, Web browsers, and so on) running on top of that. Each of these layers is relatively independent so, for example, the same Windows operating system might run on laptops running a different BIOS, while a computer running Windows (or another operating system) can run any number of different applications.

Operating systems have another big benefit. Back in the 1970 and early 1980 virtually all computers were maddeningly different. They all ran in their own, idiosyncratic ways with fairly unique hardware (different processor chips, memory addresses, screen sizes and all the rest). Programs written for one machine (such as an Apple) usually wouldn't run on any other machine (such as an IBM) without quite extensive conversion. That was a big problem for programmers because it meant they had to rewrite all their programs each time they wanted to run them on different machines. How did operating systems help? If you have a standard operating system and you tweak it so it will work on any machine, all you have to do is write applications that work on the operating system. Then any application will work on any machine. The operating system that definitively made this breakthrough was, of course, Microsoft Windows, written by Bill Gates. It's important to note that there were earlier operating systems too. You can read more of that story in our article on the history of computers.

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what is computer program?

As you can read in our long article on computer history, the first computers were gigantic calculating machines and all they ever really did was "crunch numbers": solve lengthy, difficult, or tedious mathematical problems. Today, computers work on a much wider variety of problems but they are all still, essentially, calculations. Everything a computer does, from helping you to edit a photograph you've taken with a digital camera to displaying a web page, involves manipulating numbers in one way or another.

Suppose you're looking at a digital photo you just taken in a paint or photo-editing program and you decide you want a mirror image of it in other words, flip it from left to right. You probably know that the photo is made up of millions of individual pixels colored squares arranged in a grid pattern. The computer stores each pixel as a number, so taking a digital photo is really like an instant, orderly exercise in painting by numbers! To flip a digital photo, the computer simply reverses the sequence of numbers so they run from right to left instead of left to right. Or suppose you want to make the photograph brighter. All you have to do is slide the little "brightness" icon. The computer then works through all the pixels, increasing the brightness value for each one by, say, 10 percent to make the entire image brighter. So, once again, the problem boils down to numbers and calculations.

What makes a computer different from a calculator is that it can work all by itself. You just give it your instructions (called a program) and off it goes, performing a long and complex series of operations all by itself. Back in the 1970s and 1980s, if you wanted a home computer to do almost anything at all, you had to write your own little program to do it. For example, before you could write a letter on a computer, you had to write a program that would read the letters you typed on the keyboard, store them in the memory, and display them on the screen. Writing the program usually took more time than doing whatever it was that you had originally wanted to do (writing the letter). Pretty soon, people started selling programs like word processors to save you the need to write programs yourself.

Today, most computer users buy, download, or share programs like Microsoft Word and Excel. Hardly anyone writes programs any more.

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The Importance of the main() Function in C Programming

By Dan Gookin from C All-in-One Desk Reference For Dummies
All C language programs must have a main() function. It's the core of every program. It's required. The main() function doesn't really have to do anything other than be present inside your C source code. Eventually, it contains instructions that tell the computer to carry out whatever task your program is designed to do. But it's not officially required to do anything.

The basic main() function
When the operating system runs a program in C, it passes control of the computer over to that program. This is like the captain of a huge ocean liner handing you the wheel. Aside from any fears that may induce, the key point is that the operating system needs to know where inside your program the control needs to be passed. In the case of a C language program, it's the main() function that the operating system is looking for.

At a minimum, the main() function looks like this:

main() {}
Like all C language functions, first comes the function's name, main, then comes a set of parentheses, and finally comes a set of braces, also called curly braces.

If your C program contains only this line of code, you can run it. It won't do anything, but that's perfect because the program doesn't tell the computer to do anything. Even so, the operating system found the main() function and was able to pass control to that function — which did nothing but immediately return control right back to the operating system. It's a perfect, flawless program.

Dissecting the main() function
The set of parentheses after a C language function name is used to contain any arguments for the function — stuff for the function to digest. For example, in the sqrt() function, the parentheses hug a value; the function then discovers the square root of that value.

The main() function uses its parentheses to contain any information typed after the program name at the command prompt. This is useful for more advanced programming. Beginning programmers should keep in mind what those parentheses are there for, but you should first build up your understanding of C before you dive into that quagmire.

The braces are used for organization. They contain programming instructions that belong to the function. Those programming instructions are how the function carries out its task or does its thing.

By not specifying any contents, as was done for the main() function earlier, you have created what the C Lords call a dummy function — which is kind of appropriate, given that you're reading this at Dummies.com.

Note that the basic, simple main()function doesn't require a specific keyword or procedure for ending the program. In some programming languages, an END or EXIT command is required, but not in C. In the C language, the program ends when it encounters the last brace in the main() function. That's the sign that the program is done, after which control returns to the operating system.

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Programming the ENIAC

Built in 1943-45 at the Moore School of the University of Pennsylvania for the War effort by John Mauchly and J. Presper Eckert (no relation to Columbia University's Wallace Eckert) but not delivered to the Army until just after the end of the war, the Electronic Numerical Integrator And Computer (ENIAC) was the first general-purpose electronic digital computer. It was 150 feet wide with 20 banks of flashing lights and about 300 times faster than the Mark 1 at addition. Wallace Eckert is cited in the histories as an influence on the designers, as he was for the Mark 1. These US Army photos from the archives of the ARL Technical Library show two early programmers (Gloria Ruth Gordon [Bolotsky] and Ester Gerston) at work on the ENIAC.

     
The ENIAC was not a stored-program computer; it is "better described as a collection of electronic adding machines and other arithmetic units, which were originally controlled by a web of large electrical cables" (David Alan Grier, IEEE Annals of the History of Computing, Jul-Sep 2004, p.2). It was programmed by a combination of plugboard wiring (shown at the top) and three "portable function tables", shown above (CLICK HERE and HERE for better views). Each function table has 1200 ten-way switches, used for entering tables of numbers. Note the IBM punches on the far right -- a bit hard to make out; better visible in this clearer but less atmospheric copy of the same photo. Franz Alt writes in Archaeology of Computers -- Reminiscences, 1945-47, Communications of the ACM, July 1972:

One of the peculiarities that distinguished ENIAC from all later computers was the way in which instructions were set up on the machine. It was similar to the plugboards of small punched-card machines, but here we had about 40 plugboards, each several feet in size. A number of wires had to be plugged for each single instruction of a problem, thousands of them each time a problem was to begin a run; and this took several days to do and many more days to check out. When that was finally accomplished, we would run the problem as long as possible, i.e. as long as we had input data, before changing over to another problem. Typically, changeovers occurred only once every few weeks.


Later, ENIAC's plugboards were permanently "microprogrammed" with a repertoire of 50-100 commonly used instructions that could be referenced from a "user program" entered as a sequence of instructions into the function-table switches. [40]

Herb Grosch says of this page [10 May 2003]:

I was roaming around the links and sublinks in the ENIAC story, and note with much interest that there were three or four castered twiddle boards [portable function tables A, B, and C], where I had always assumed only one.
I note the almost complete absence of Col.[then Major] Simon, and of Dick Clippinger, who should share with von Neumann the credit for moving from plugging to twiddling for program insertion.

I was pleased to see short reference to the IBM I/O units, which show in your and other copies of the most famous photo. I wonder if John McPherson knows how they were sold/rented/given to the Moore School --- never thought to ask him at the time. Unusual.

Bashe [4] says, "When the Army requested special card reading and punching units for an undisclosed project underway at the University of Pennsylvania, [IBM Chief Engineer James W.] Bryce and his staff coordinated IBM's response... In 1946, the instrument produced by the project was revealed as ENIAC..."
Not on your page, but in the Richie story and other Aberdeeneries there should have [been made] mention of the astronomer who taught them how to calculate trajectories by hand: Forest Ray Moulton, circa 1920 [my p.89].

That prolly wasn't intentional, but the elision of all references to the big punched card shop Cunningham ran, and to the two relay machines IBM built, certainly was. Those are what actually did firing tables, after desk calculators were overwhelmed and until the Bell machine arrived, and until ENIAC was moved in and later freed up.

Now, about the "I'm dubious ..." above. I don't think Wallace Eckert had any influence whatsoever on the designers of the ENIAC or the ASCC. Certainly in the hundreds and hundreds of hours he and I talked about those two machines, he never mentioned such, nor did Frank Hamilton, who was Number Two on the ASCC, ever hint at the latter.

A 1938 meeting between ASCC's Howard Aiken and Wallace Eckert is well known [9]. Gutzwiller [90] says that Presper Eckert (among other well-known pioneers of computing including Aiken and Vannevar Bush) got his first inspiration from Wallace Eckert's 1940 "orange book". I have not been able to pin down any evidence of direct contact between the two Eckerts. Since ENIAC was a war project (as was the Aberdeen Relay Calculator, with which Eckert was also ostensibly involved) it would not be surprising that records are not available.

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Multi function device (MFD)

A product or device that has multiple functions. An example of this might be a printer that also makes copies, faxes, and scans. Another example is a CD or DVD that might contain multiple applications on the same disk; this may be a Mac and PC version of the same software or media meant to be played on more than one platform. Also called multi function product (MFP), all-in-one.

Read more: http://www.businessdictionary.com/definition/multi-function-device-MFD.html#ixzz3wM5ABYwc.

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Function of computer hardware components

A processor is the brains of any computer system. Also known as a CPU or central processing unit it is used to execute instructions that enable the operating system and application software to run on a system. A processor performs arithmetic and logical calculations in the ALU (arithmetic logical unit) and control instructions in the control unit. The processor communicates with storage devices such as the hard drive and RAM to process information used to control the operating system and applications that run on a computer system. Processors are being made smaller and faster all the time and this allows systems to carry out instructions faster and perform better. A processor in a mission critical system used in space or a medical device needs to be very powerful to carry out instructions quickly.

Processors are integrated into a computer system by placing them on the motherboard. A Motherboard is like the body of a computer system it contains a socket to house the processor and links a lot of internal components together such as RAM and graphics cards using communication buses. The have integrated controllers to enable the processor to communicate with storage devices such as HDDs and CD/DVD drives. A motherboard is a printed circuit board (PCB) and links the components using lines drawn on the circuit board. Motherboards contain expansion slots to insert RAM or graphics, sound and network cards to improve system performance. They allow a computer engineer to upgrade the RAM so that a machine runs faster. Motherboards also contain sockets to enable a computer system to communicate with external devices using USB ports, sound jacks and VDU outputs. A motherboard comes in different form factors (this is the shape and size) and you need to check if components are compatible with this form factor before purchasing them. A phone also has a motherboard which is much smaller than that used in a PC obviously. PC motherboards normally require them to be cooled to keep components running at optimal performance. This is done using fans and heat sinks.

BIOS or basic input/output system is firmware (firmware links hardware and software) built into a computer system. The BIOS is used to ensure that a system boots up correctly and all hardware components are configured to work correctly. It contains information about the hardware components connected to the system such as keyboard and mouse and enables applications installed on the system to be controlled by the hardware. The BIOS is stored in non-volatile ROM (read only memory) of a system and is configured to allow that motherboard and all connected components and peripherals to run correctly.

A power supply or PSU (power supply unit) is used to power all of the components in a computer system. The power supply runs from 120 or 240 volts mains supplied and provides 12v, 5v and sometimes 3.3v outputs to power different components. A hard drive needs a power supply to run and the PSU has a specific output connector that can be used to connect to different hard drive types. Standard connectors are ATX – you can find out more by researching the different type of connectors that power supplies have. They normally range from between £20 to £50 in price.

A fan is used in a computer system to suck hot air out of the system to make sure that it does not overheat. Most computer systems will have fans on the casing to suck the hot air out of the system. The fans are connected to the power supply. Most processors also have a fan connected to them to draw the heat away from them and ensure the operate at the best speed possible. You will hear a system that is getting hot become noisy as the fans increase in speed. Heat sinks are also used to keep systems cool. Heat sinks are made from materials that draw heat away such as aluminium and copper. Often a heat sink is placed on top of a processor to draw the heat away from it. A fan will be placed on top of the heat sink to continuously draw out the heat that the processor produces. This heat is then drawn away from the systems by fans placed on the casing. Sometimes water is used to cool systems that are prone to heating up – you can investigate this further to see how water cooling is used in gaming systems as an example.

For a computer system to run it needs a storage system to store information about the operating system and applications. Knowledge of hard drive configuration and controllers is an important skill to have when setting up a system. There are different ways to communication with HDDs (hard disk drives) such as SATA, IDE or EIDE. SATA or Serial ATA (Serial Advanced Technology Attachment) is a serial communications method that communicates over a serial cable. If your motherboard is configured with SATA then you need to buy a SATA compliant HDD. IDE (integrated drive electronics) that has the controller for the hard drive stored on the drive itself. Master/slave configuration is used when installing an additional HDD on your computer system. The master/slave hard drive configuration means that both drives can be controlled using a single cable. The IDE controllers in each HDD talk to each other to say when it is ok for the system to send or receive data to and from the storage device. If the master drive is in use it will send a message to the slave to tell it that. When the master drive is finished communicating with the system it will send a message to say that the communications are complete and the slave can go ahead and perform the required actions. This is normally configured using hardware jumpers to say with is the master and which is the slave drive.

Most computer systems use ports such as USB, parallel and serial to communicate with external devices. A USB (universal serial bus) port allows you to plugin in an external storage device such as a keyboard or mouse to connect to the motherboard and enable the user to control the system. The motherboard comes with a USB controller chip to enable the communication to take place. Parallell ports were initially used for printers and are not as common these days. They are used for devices that need a lot of communication such as a plotter used in sign writing. The have more communication lines than a serial port and therefore can send and receive more data.

In order to explain the function of computer hardware components in full it is important to consider the internal memory components of a computer system. The three main types of internal memory in a computer system are RAM, ROM and cache. RAM or random access memory is memory that linked to a processor on the motherboard. Data can be written to and read from random access memory at roughly the same speed. RAM chips are stored on separate printed circuit boards that can be plugged into a system motherboard. Applications write data to the RAM chips based on current operations. RAM is wiped when a systems shuts down. For example, if a large amount of data is copied on to the clipboard it would be stored in random access memory. If you do not clear the clipboard the information will still be available to paste in an hour or even week’s time but if the system shuts down the information will not be available to paste as the RAM will be cleared. RAM upgrades can increase system performance as more applications can be used at the same time with less impact on system resources. ROM or read only memory contains system information such as the BIOS (although some bios is stored directly on the motherboard itself). Although it is considered read only it can be configured in some sense like setting the BIOS password. ROM also stores information about the operating and other programs stored on the system. ROM does not get wiped when a system reboots. Cache memory is ram that can be accessed much quicker than regular RAM that is slotted into a motherboard on a computer system. Cache is normally stored within the CPU or on a separate cache memory chip located right beside the CPU. Cache has different levels high speed and ultra high speed. L1 or level 1 cache is normally stored on the CPU chip and is the fastest type of cache. Cache memory is used by the processor to carry out instructions more quickly as data can be accessed by the processor quicker due to the proximity of the cache and ultra high speed.

Specialised cards such as network and graphic cards are used to increase the functionality and performance of a computer system. Some motherboards come with integrated graphics meaning that the graphics driver is stored on the motherboard. For better graphical performance a specialised graphics card with increase the performance in terms of outputting a better quality and higher resolution picture from your computer system. Installing a specialised graphics card would be important for someone like a movie editor who wanted to see the full impact of high definition video when editing. A network card can be plugged into an expansion slot to enable a computer system to connect to a network. This can be an internal network or the world wide web. Again some motherboards come with integrated networking capability but installing a specialised NIC (network interface card) will increase performance in terms of connection speed etc.

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FAQs by Program Directors about Computer Matching

What does a computer matching program do?

A matching program serves as a clearinghouse to help applicants obtain supervised practice positions of their choice and to help Dietetic Internships (DI) obtain applicants of their choice. It eliminates unfair pressures and premature decisions in appointments by programs and acceptance or rejection of appointments by applicants. Academy of Nutrition and Dietetics has contracted with D&D Digital to facilitate matching through a computerized process.

Computer matching simulates all the steps of the traditional selection process using the rank order lists submitted by applicants and programs, but eliminates the pressures in making decisions. As a result, each applicant receives a position with the highest ranked program that offers the applicant a position. Each program is matched to the maximum number of positions to be filled with the highest ranked applicants who do not receive offers from programs they prefer.

Who screens applications and decides which candidates are acceptable to a particular program?

Each DI screens its own applications and submits a priority listing of acceptable applicants to D&D Digital, along with the number of positions to be filled. The program's priority listing should include more names than there are positions available to ensure that all positions are filled.

Programs are encouraged to rank all applicants that they would accept into their program on their priority list. A program will not be matched to an applicant whose name does not appear on the program's priority listing. Nor will an applicant be matched to a program that is not on the applicant's priority listing.

Will the applicants or programs know how the other has ranked them?

No. All information submitted to D&D Digital is kept confidential. Each applicant is given the final result of the matching. Each program is provided with the names of the applicants it obtains in the match. Programs and applicants are not told how they were ranked by each other.

Who is responsible for the acceptance and rejection notice to applicants?

D&D Digital provides personal notification of placement or lack of placement to each applicant via their website. It also provides each program director with a list of applicants matched to its program. Applicants who receive a match are required to notify the program by appointment day to accept or reject the appointment.

What can a program do if computer matching does not fill all its positions?

D&D Digital sends a listing of unmatched applicants who have agreed to release their names to each program following the matching. Programs may contact unmatched applicants or return to their applicant pool to fill positions only after appointment day has occurred (see Dietetic Internship Program Director Responsibilities for entire process).

Who pays for computer matching?

All costs are borne by the applicant. Applicants must pay a $50.00 fee when submitting their rank order lists to D&D Digital.

What do students need to do to be considered for a DI appointment?

Students should be advised that there are two components. First, they must apply to each DI for which they seek admission. Most programs use DICAS, the online application. The second component is the appointment process. Most DIs are participating in computer matching. The remaining programs accept applications only from individuals employed by the sponsoring institution. These individuals should not be participating in computer matching. These programs are noted as exempt from computer matching in the directory of accredited programs.

Can a student apply to more than one track of a single program?

Yes. There are programs with more than one track. These may have two or more computer matching codes, one for each option. The applicant needs to rank the options according to preference when they submit their priority choices.

Is there a limit to the number of programs that one can apply to and rank for computer matching?

There is no limit to the number of programs selected. However, the applicant must submit an application to each program. Many programs charge an application fee and DICAS charges a fee for each program selected to submit an application.

What process is used for the matching?

Before matching begins, the applicants' preference lists and the DI preference lists are "cleaned." If a program does not rank an applicant, that program is removed from the applicant's list. If an applicant does not rank a program, the applicant is removed from the program's list. Then, the matching occurs using the student's prioritized list and the programs' prioritized lists until all possible matches are complete. The process is explained in detail on the D&D Digital website.

If a student submits the priority choices and fee for the computerized match process, but changes his/her plans, how should this be handled?

If the student has submitted the priority choices and then changes his/her career plans, he/she must notify D&D Digital in writing or by email prior to the deadline date of their decision to withdraw from the matching process. Applicants must check the Computer Matching Calendar to obtain deadline dates each matching cycle.

Do some students receive matches to more than one DI?

No. Students are given only one match, the highest priority choice on their list for which a program match occurs.

Can a program require acceptance into a graduate program in conjunction with the DI and still participate in computer matching?

Yes. Applicants should be advised to submit the application to the graduate school at the same time the DI application is submitted. The program's list of preferred applicants should include only those who also meet the graduate school requirements.

Our program admits applicants during each of four academic quarters. It is difficult for us to participate in a selection process with only two appointment dates.

You can request two different codes for each of the two appointment dates. The codes will correspond to the quarterly admission dates for your program. Thus, you will be able to select students for summer and fall start dates in April and for winter and spring start dates in November.

Which DI programs are participating in computer matching?

All DIs are participate in computer matching except those programs granted an exemption from computer matching because they only accept applications from individuals employed by the sponsoring organization. The online directory of Dietetic Internships notes those participating in computer matching and those programs that are exempt. Applicants to these programs are not expected to be applying to other supervised practice programs or participating in the computer matching appointment process.

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Computers: History, Components and Future

When you think about computers, you probably think about your home computer, your laptop or even a notepad. Your home computers can do everything from send a letter to plan your next vacation to Disney World. You can download music and watch movies!

Cartoon Computer Image - Science for Kids All About Computers

Your home computers can do everything from send a letter to plan your next vacation to Disney World. Find out more all about computers below.

The first computers weren’t so fancy. In fact, one of the first computer was an abacus. Invented in Babylon in 500 B.C., the abacus was made of string and beads. Its only purpose was to count and keep track of money and other things. In the 1600s, two inventors made calculators that ran with gears and wheels.

Abacus Computer Image

In fact, one of the first computer was an abacus. Invented in Babylon in 500 B.C., the abacus was made of string and beads.

In 1833, Charles Babbage invented all the parts a modern computer uses, but it wasn’t until 120 years later that the first modern computers were invented. These first computers were huge and took up a whole room. The beginnings of computers as we know them happened in 1980 – only 30 years ago.

main-parts-of-computer-hardware image

Main parts of computer hardware.

Fun Facts about Computers for Kids

A computer is a machine that takes input from the user and gives output. So, you give the computer a command and it follows it to produce a result.

Computers have a microprocessor that can make calculations instantly. Lots of things have microprocessors, such as your car, your washing machine, your dishwasher and even your television.

Computers have memory or RAM, which stores items on the computer when they’re not in use. The processor stores everything your computer needs to run.

As computers run, they get hot. Computers have fans to keep them cool.

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Part of Computer

If you use a desktop computer, you might already know that there isn't any single part called the "computer." A computer is really a system of many parts working together. The physical parts, which you can see and touch, are collectively called hardware. (Software, on the other hand, refers to the instructions, or programs, that tell the hardware what to do.)

The following illustration shows the most common hardware in a desktop computer system. Your system might look a little different, but it probably has most of these parts. A laptop computer has similar parts but combines them into a single, notebook-sized package.

                                                                                            Part of Computer

Picture of a desktop computer system                                 

Desktop computer system

Let's take a look at each of these parts.                           

System unit

The system unit is the core of a computer system. Usually it's a rectangular box placed on or underneath your desk. Inside this box are many electronic components that process information. The most important of these components is the central processing unit (CPU), or microprocessor, which acts as the "brain" of your computer. Another component is random access memory (RAM), which temporarily stores information that the CPU uses while the computer is on. The information stored in RAM is erased when the computer is turned off.

Almost every other part of your computer connects to the system unit using cables. The cables plug into specific ports (openings), typically on the back of the system unit. Hardware that is not part of the system unit is sometimes called a peripheral device or device.

Picture of a system unit

System unit

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Storage

Your computer has one or more disk drives—devices that store information on a metal or plastic disk. The disk preserves the information even when your computer is turned off.

Hard disk drive

Your computer's hard disk drive stores information on a hard disk—a rigid platter or stack of platters with a magnetic surface. Because hard disks can hold massive amounts of information, they usually serve as your computer's primary means of storage, holding almost all of your programs and files. The hard disk drive is normally located inside the system unit.

Picture of a hard disk drive

Hard disk drive

CD and DVD drives

Nearly all computers today come equipped with a CD or DVD drive, usually located on the front of the system unit. CD drives use lasers to read (retrieve) data from a CD; many CD drives can also write (record) data onto CDs. If you have a recordable disk drive, you can store copies of your files on blank CDs. You can also use a CD drive to play music CDs on your computer.

Picture of a CD

CD

DVD drives can do everything that CD drives can, plus read DVDs. If you have a DVD drive, you can watch movies on your computer. Many DVD drives can record data onto blank DVDs.

Tip

If you have a recordable CD or DVD drive, periodically back up (copy) your important files to CDs or DVDs. That way, if your hard disk ever fails, you won't lose your data.

Floppy disk drive

Floppy disk drives store information on floppy disks, also called floppies or diskettes. Compared to CDs and DVDs, floppy disks can store only a small amount of data. They also retrieve information more slowly and are more prone to damage. For these reasons, floppy disk drives are less popular than they used to be, although some computers still include them.

Picture of a floppy disk

Floppy disk

Why are these disks called "floppy" disks? The outside is made of hard plastic, but that's just the sleeve. The disk inside is made of a thin, flexible vinyl material.

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Mouse

A mouse is a small device used to point to and select items on your computer screen. Although mice come in many shapes, the typical mouse does look a bit like an actual mouse. It's small, oblong, and connected to the system unit by a long wire that resembles a tail. Some newer mice are wireless.

Picture of a computer mouse

Mouse

A mouse usually has two buttons: A primary button (usually the left button) and a secondary button. Many mice also have a wheel between the two buttons, which allows you to scroll smoothly through screens of information.

Picture of mouse pointers

Mouse pointers

When you move the mouse with your hand, a pointer on your screen moves in the same direction. (The pointer's appearance might change depending on where it's positioned on your screen.) When you want to select an item, you point to the item and then click (press and release) the primary button. Pointing and clicking with your mouse is the main way to interact with your computer. For more information, see Using your mouse.

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Keyboard

A keyboard is used mainly for typing text into your computer. Like the keyboard on a typewriter, it has keys for letters and numbers, but it also has special keys:

The function keys, found on the top row, perform different functions depending on where they are used.

The numeric keypad, located on the right side of most keyboards, allows you to enter numbers quickly.

The navigation keys, such as the arrow keys, allow you to move your position within a document or webpage.

Picture of a keyboard

Keyboard

You can also use your keyboard to perform many of the same tasks you can perform with a mouse. For more information, see Using your keyboard.

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Monitor

A monitor displays information in visual form, using text and graphics. The portion of the monitor that displays the information is called the screen. Like a television screen, a computer screen can show still or moving pictures.

There are two basic types of monitors: CRT (cathode ray tube) monitors and the newer LCD (liquid crystal display) monitors. Both types produce sharp images, but LCD monitors have the advantage of being much thinner and lighter.

Picture of an LCD monitor and a CRT monitor

LCD monitor (left); CRT monitor (right)

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Printer

A printer transfers data from a computer onto paper. You don't need a printer to use your computer, but having one allows you to print e‑mail, cards, invitations, announcements, and other material. Many people also like being able to print their own photos at home.

The two main types of printers are inkjet printers and laser printers. Inkjet printers are the most popular printers for the home. They can print in black and white or in full color and can produce high-quality photographs when used with special paper. Laser printers are faster and generally better able to handle heavy use.

Picture of an inkjet printer and a laser printer

Inkjet printer (left); laser printer (right)

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Speakers

Speakers are used to play sound. They can be built into the system unit or connected with cables. Speakers allow you to listen to music and hear sound effects from your computer.

Picture of computer speakers

Computer speakers

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Modem

To connect your computer to the Internet, you need a modem. A modem is a device that sends and receives computer information over a telephone line or high-speed cable. Modems are sometimes built into the system unit, but higher-speed modems are usually separate components.

Picture of a cable modem

Cable modem

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Disadvantages of internet

1) There is a lot of wrong information on the internet. Anyone can post anything, and much of it is garbage. 

2) There are predators that hang out on the internet waiting to get unsuspecting people in dangerous situations. 

3) Some people are getting addicted to the internet and thus causing problems with their interactions of friends and loved ones. 

4) Pornography that can get in the hands of young children too easily. 

5) Easy to waste a lot of time on the internet. You can start surfing, and then realize far more time has passed than you realized. Internet and television together of added to the more sedentary lifestyles of people which further exacerbates the obesity problem. 

6) Internet has a lot of "cheater" sites. People can buy essays and pass them off as their own far more easily than they used to be able to do. 

7) There are a lot of unscrupulous businesses that have sprung up on the internet to take advantage of people. 

8) Hackers can create viruses that can get into your personal computer and ruin valuable data. 

9) Hackers can use the internet for identity theft. 

10) It can be quite depressing to be on the internet and realize just how uneducated so many people have become in today's society.

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Advantages of internet

1) Information on almost every subject imaginable. 

2) Powerful search engines 

3) Ability to do research from your home versus research libraries. 

4) Information at various levels of study. Everything from scholarly articles to ones directed at children. 

5) Message boards where people can discuss ideas on any topic. Ability to get wide range of opinions. People can find others that have a similar interest in whatever they are interested in. 

6) The internet provides the ability of emails. Free mail service to anyone in the country. 

7) Platform for products like SKYPE, which allow for holding a video conference with anyone in the world who also has access. 

8) Friendships and love connections have been made over the internet by people involved in love/passion over similar interests. 

9) Things such as Yahoo Answers and other sites where kids can have readily available help for homework. 

10) News, of all kinds is available almost instantaneously. Commentary, on that news, from every conceivable viewpoint is also available. 

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Internet

Internet

  

Definition

A means of connecting a computer to any other computer anywhere in the world via dedicated routers and servers. When two computers are connected over the Internet, they can send and receive all kinds of information such as text, graphics, voice, video, and computer programs.

No one owns Internet, although several organizations the world over collaborate in its functioning and development. The high-speed, fiber-optic cables (called backbones) through which the bulk of the Internet data travels are owned by telephone companies in their respective countries.

The Internet grew out of the Advanced Research Projects Agency's Wide Area Network (then called ARPANET) established by the US Department Of Defense in 1960s for collaboration in military research among business and government laboratories. Later universities and other US institutions connected to it. This resulted in ARPANET growing beyond everyone's expectations and acquiring the name 'Internet.'

The development of hypertext based technology (called World Wide web, WWW, or just the Web) provided means of displaying text, graphics, and animations, and easy search and navigation tools that triggered Internet's explosive worldwide growth.

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Function of Programming

Functions

Functions "Encapsulate" a task (they combine many instructions into a single line of code). Most programming languages provide many built in functions that would otherwise require many steps to accomplish, for example computing the square root of a number. In general, we don't care how a function does what it does, only that it "does it"!

When a function is "called" the program "leaves" the current section of code and begins to execute the first line inside the function. Thus the function "flow of control" is:

The program comes to a line of code containing a "function call".

The program enters the function (starts at the first line in the function code).

All instructions inside of the function are executed from top to bottom.

The program leaves the function and goes back to where it started from.

Any data computed and RETURNED by the function is used in place of the function in the original line of code.

Why do we Write Functions?

They allow us to conceive of our program as a bunch of sub-steps. (Each sub-step can be its own function. When any program seems too hard, just break the overall program into sub-steps!)

They allow us to reuse code instead of rewriting it.

Functions allow us to keep our variable namespace clean (local variables only "live" as long as the function does). In other words, function_1 can use a variable called i, and function_2 can also use a variable called i and there is no confusion. Each variable i only exists when the computer is executing the given function.

Functions allow us to test small parts of our program in isolation from the rest. This is especially true in interpreted langaues, such as Matlab, but can be useful in C, Java, ActionScript, etc.

Steps to Writing a Function

Understand the purpose of the function.

Define the data that comes into the function from the caller (in the form of parameters)!

Define what data variables are needed inside the function to accomplish its goal.

Decide on the set of steps that the program will use to accomplish this goal. (The Algorithm)

Parts of a "black box" (i.e., a function)

Functions can be called "black boxes" because we don't need to know how they work. Just what is supposed to go into them, and what is supposed to come out of them.

When defining a program as a black box, we must describe the following attributes of the function.

Note: most documentation systems are just this, the attributes of a function with no code associated with it.

The Name - describes the purpose of the function. Usually a verb or phrase, such as "compute_Average", or just "average".

The Inputs - called parameters. Describe what data is necessary for the function to work and gives each piece of data a Symbolic Name for use in the function.

The Calculation - varies for each function

The Output - Usually one (but sometimes zero or sometimes many) values that are calculated inside the function and "returned" via the output variables.

Function Workspace

Every function has its own Workspace. This means that every variable inside the function is only usable during the execution of the function (and then the variables go away).

Having a separate "workspace" for each function is critical to proper software engineering. If every function shared every variable in an entire program, it would be easy to inadvertently change the values of variables that you shouldn't. Further, it would be hard to remember what "names" have been used elsewhere, and coming up with new names to represent similar ideas would be challenging.

A side-effect of function variables not existing after the end of the function is that the only way to get information "out" of a function is by "returning" that information via the output of the function.

Additionally, the function can only "see" the information that is "passed" to it via parameters. Thus the only way information can get "in" to the function is by using parameters.

Note: In certain object oriented languages (e.g., C++, Java, ActionScript), a function can also see all of the variables associated with its containing object.

Formal vs. Actual Parameters

When we create a function, it should represent a "generic" action that can be applied in many circumstances. For example, if we want to find the average grade, it doesn't matter if it is on a test, or on a quiz, or an assignment, or a midterm, etc... given any list of grades we can compute an average!

...but if it can be any list of grades, how do we know what the list of grades will be called? The answer: we don't care. You, the programmer of the function, provide your own name for the data. This is much the same as when a sales person calls you and reads a script trying to sell something to you, they say: Dear _insert customer name here_, let me sell you our wonderful product.

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Internal Computer Hardware

Computer Hardware is the physical part of a computer, as distinguished from the computer software that executes or runs on the hardware. The hardware of a computer is infrequently changed, while software and data are modified frequently. The term soft refers to readily created, modified, or erased. These are unlike the physical components within the computer which are hard.

When you think of the term computer hardware you probably think of the guts inside your personal computer at home or the one in your classroom. However, computer hardware does not specifically refer to personal computers. Instead, it is all types of computer systems. Computer hardware is in embedded systems in automobiles, microwave ovens, CD players, DVD players, and many more devices. In 2003, only 0.2% of all microprocessors sold were for personal computers. How many other things in your house or your classroom use computer hardware?

Inside Computer

Motherboard

The motherboard is the body or mainframe of the computer, through which all other components interface. It is the central circuit board making up a complex electronic system. A motherboard provides the electrical connections by which the other components of the system communicate. The mother board includes many components such as: central processing unit (CPU), random access memory (RAM), firmware, and internal and external buses.

Motherboard

Central Processing Unit

The Central Processing Unit (CPU; sometimes just called processor) is a machine that can execute computer programs. It is sometimes referred to as the brain of the computer.

CPU Diagram

There are four steps that nearly all CPUs use in their operation: fetch, decode, execute, and writeback. The first step, fetch, involves retrieving an instruction from program memory. In the decode step, the instruction is broken up into parts that have significance to other portions of the CPU. During the execute step various portions of the CPU, such as the arithmetic logic unit (ALU) and the floating point unit (FPU) are connected so they can perform the desired operation. The final step, writeback, simply writes back the results of the execute step to some form of memory.

Random Access Memory

Random access memory (RAM) is fast-access memory that is cleared when the computer is power-down. RAM attaches directly to the motherboard, and is used to store programs that are currently running. RAM is a set of integrated circuits that allow the stored data to be accessed in any order (why it is called random). There are many different types of RAM. Distinctions between these different types include: writable vs. read-only, static vs. dynamic, volatile vs. non-volatile, etc.

RAM

Firmware

Firmware is loaded from the Read only memory (ROM) run from the Basic Input-Output System (BIOS). It is a computer program that is embedded in a hardware device, for example a microcontroller. As it name suggests, firmware is somewhere between hardware and software. Like software, it is a computer program which is executed by a microprocessor or a microcontroller. But it is also tightly linked to a piece of hardware, and has little meaning outside of it. Most devices attached to modern systems are special-purpose computers in their own right, running their own software. Some of these devices store that software (“firmware”) in a ROM within the device itself

Power Supply

The power supply as its name might suggest is the device that supplies power to all the components in the computer. Its case holds a transformer, voltage control, and (usually) a cooling fan. The power supply converts about 100-120 volts of AC power to low-voltage DC power for the internal components to use. The most common computer power supplies are built to conform with the ATX form factor. This enables different power supplies to be interchangable with different components inside the computer. ATX power supplies also are designed to turn on and off using a signal from the motherboard, and provide support for modern functions such as standby mode.

Removable Media Devices

If your putting something in your computer and taking it out is most likely a form of removable media. There are many different removable media devices. The most popular are probably CD and DVD drives which almost every computer these days has at least one of. There are some new disc drives such as Blu-ray which can hold a much larger amount of information then normal CDs or DVDs. One type of removable media which is becoming less popular is floppy disk.

CD

CDs are the most common type of removable media. They are inexpensive but also have short life-span. There are a few different kinds of CDs. CD-ROM which stands for Compact Disc read-only memory are popularly used to distribute computer software although any type of data can be stored on them. CD-R is another variation which can only be written to once but can be read many times. CD-RW (rewritable) can be written to more than once as well as read more than once. Some other types of CDs which are not as popular include Super Audio CD (SACD), Video Compact Discs (VCD), Super Video Compact Discs (SVCD), PhotoCD, PictureCD, CD-i, and Enhanced CD.

CD-ROM Drive

There are two types of devices in a computer that use CDs: CD-ROM drive and a CD writer. The CD-ROM drive used for reading a CD. The CD writer drive can read and write a CD. CD writers are much more popular are new computers than a CD-ROM drive. Both kinds of CD drives are called optical disc drives because the use a laser light or electromagnetic waves to read or write data to or from a CD.

DVD

DVDs (digital versatile discs) are another popular optical disc storage media format. The main uses for DVDs are video and data storage. Most DVDs are of the same dimensions as compact discs. Just like CDs there are many different variations. DVD-ROM has data which can only be read and not written. DVD-R and DVD+R can be written once and then function as a DVD-ROM. DVD-RAM, DVD-RW, or DVD+RW hold data that can be erased and re-written multiple times. DVD-Video and DVD-Audio discs respectively refer to properly formatted and structured video and audio content. The devices that use DVDs are very similar to the devices that use CDs. There is a DVD-ROM drive as well as a DVD writer that work the same way as a CD-ROM drive and CD writer. There is also a DVD-RAM drive that reads and writes to the DVD-RAM variation of DVD.

DVD

Blu-ray

Blu-ray is a newer optical disc storage media format. Its main uses are high-definition video and data storage. The disc has the same dimensions as a CD or DVD. The term “Blu-ray” comes from the blue laser used to read and write to the disc. The Blu-ray discs can store much more data then CDs or DVDs. A dual layer Blu-ray disc can store up to 50GB, almost six times thecapacity of a dual layer DVD (WOW!). Blu-ray discs have similar devices used to read them and write to them as CDs have. A BD-ROM drive can only read a Blu-ray disc and a BD writer can read and write a Blu-ray disc.

Floppy Disk

A floppy disk is a type of data storage that is composed of a disk of thin, flexible(“floppy”) magnetic storage medium encased in a square or rectangular plastic shell. Floppy disks are read and written by a floppy disk drive. Floppy disks are a dying and being replaced by the optical and flash drives. Many new computers do not come with floppy drives anymore but there are a lot of older ones with floppy drives lying around. While floppy disks are very cheap the amount of storage on them compared to the amount of storage for the price of flash drives makes floppy disks unreasonable to use.

Floppy Disk

Internal Storage

Internal storage is hardware that keeps data inside the computer for later use and remains persistent even when the computer has no power. There are a few different types of internal storage. Hard disks are the most popular type of internal storage. Solid-state drives have grown in popularity slowly. A disk array controller is popular when you need more storage then a single har disk can hold.

Hard Disk Drive

A hard disk drive (HDD) is a non-volatile storage device which stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Just about every new computer comes with a hard disk these days unless it comes with a new solid-state drive. Typical desktop hard disk drives store between 120 and 400GB, rotate at 7,200 rpm, and have a madia transfer rate of 1 Gbit/s or higher. Hard disk drives are accessed over one of a number of bus types, including parallel ATA(also called IDE), Serial ATA (SATA), SCSI, Serial Attached SCSI, and Fibre Channel.

Hard Drive

Solid-State Drive

A solid-state drive (SSD) is a data storage device that uses solid-state memory to store persistent data. An SSD emulates a hard disk drive, thus easily replacing it in any application. SSDs have begun to appear in laptops because they can be smaller than HDDs. SSDs are currently more expensive per unit of capacity than HDDs which is why they have not caught on so quickly.

Disk Array Controller

A disk array controller is a device which manage the physical disk drives and presents them to the computer as logical units. It almost always implements hardware RAID. RAID (Redundant Array of Independent Drives) is a technology that employs the simultaneous use of two or more hard disk drives to achieve greater levels of performance, reliability, and/or larger data volume sizes. A disk array controller also provides additional disk cache.

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Hardware Components

Let's start with the computer case. This is the metal enclosure that contains many of the other hardware components. It comes in various shapes and sizes, but a typical tower model is between 15-25 inches high. Want to know what's inside? Okay, go get a screwdriver and let's open it up. Seriously, if you are really into computers, the best way to learn is to actually get hands-on. To save us some time, however, have a look at this desktop computer case. A computer enthusiast replaced the metal side panel with a transparent one, so we can have a look inside.

Although that photo looks pretty cool, it is a bit hard to recognize the individual components, especially with all the connecting wires running through it. This figure shows a more schematic version of a desktop computer, which makes it easier to point out the essential hardware components.

The computer case contains a power supply unit (#6) to convert general-purpose electricity to direct current for the other components. The most critical component is the motherboard (#2), a plastic board on which several essential components are mounted. This includes the central processing unit, or CPU.

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Disadvantages of Computer

* Computer is highly dependent on the quality of input data fed to it. Though computers are very fast in tasks that are pre-programmed, it lake the ability of human brain to detect and correct errors that it is not specifically programmed to do.

* The task of programming a computer for a computer application is very costly and time consuming. This reduces the utility of computers for applications that are non-repetitive.

* Computer systems are rather rigid. Once a computers system is designed and programmed,making even minor corrections or improvements can be quite costly and time consuming. For this reason a great care is required in design and development of computer systems.

* Computers require use of sophisticated equipment and support facilities. For example, a person solving a problem of maths using just a pen and paper can carry these with him or her anywhere with ease. However if the same problem is to be solved using a computer, the person will not only need access to a suitable computer, it will also be necessary to have the required software and suitable electric power to run the computer.

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