What Is CRT (cathode Ray Tube)

CRT (cathode Ray Tube)
Monitors Of this type screen are used commonly in homes. colleges abd offices.  these Monitors are big and require big area to place, power and have weight more than 10 pounds. We Cannot move these Moniotrs Easily.

Modem TroubleShooting

-Modems like everything else do go nuts on you. For the most part the troubles are just with the software driver or just invalid settings. There is also a chance that another device is conflicting with the modem you have. For some reason my mouse has come into this picture before causing problems. If you are experiencing a problem with your modem such as conflicts with resources, try changing COM ports. This can fix your problem in most cases. If this doesn't help or you think that your modem is software related, reinstall the modem's driver. This can be done with the software that came with the modem.

-Change Com Ports-

1. At start menu click settings
2. Click control panel
3. click modem's
4. highlight your modem and then click properties
5. select a unused COM port for the modem and hit OK

-If you are having problems with dialing your internet provide check and make sure the properties are correct in your dial up networking.

1. At start menu
2. click programs
3. click accessories
4. click communications or dial up networking

-This varies from windows 95 and 98. If lost go to settings>control panel> dial up networking.

      5.  Double click your ISP (internet service provider) connection. Verify all information on the tabs is correct with your ISP.

This seems to be the most common problem when connecting to the internet. It usually is a IP number that is wrong or not added. You may have your login name wrong or password.

-If you are having problems with a faulty driver or just plain don't have one. You can reinstall or install one this way. There are other methods that are easier. Try using the installation disk first. If this don't work then do it manually.

1. At start menu click settings
2. Click control panel
3. click system
4. click device tab
5. click on your modem in the list
6. click for properties of the modem
7. click update drive or a driver tab
8. have installation disk ready let it search for the driver and reinstall it for you.

Floppy Disk and Zip Disk Drives

Computer Hard Drives - External Hard Drive - Hard Drive - Floppy Disk - Hard Disk - Zip Disk - Floppy - Data Storage - Storage 

Floppy Disk

A floppy disk is a magnetic storage media. The floppy disk is a plastic disk coated on both side with magnetic recording material (ferrous oxide). It is also called simply a diskette. IBM invented the floppy disk in 1972. The size of the first floppy disk was 8-inch and had flexible plastic cover. Next generation of floppies was 5.25 inches disk. Today, the standard floppy disk size of 3.5 inch and has a rigid plastic cover. The size of disk refers to the diameter of disk and not refers to the storage capacity. The high-density disks are smaller in size but larger in storage capacity. The storage capacity of floppy disk is very low (i.e. maximum storage capacity is 1.44 MB).

Typically, floppy disks are used to transfer small files to and from personal computers. Floppy disk is also used in some digital cameras to store pictures. Today, floppy disks are not widely used as they were ten years ago because of their low storage capacity. The maximum age of floppy disk is about 7 years.

Today, most commonly used floppy disk is 3.5 inch diameter diskette. It is also referred to as Micro Floppy Diskette. It is enclosed in a hard plastic jacket. The read/write window of micro disk is always closed with a Metal Shutter. The shutter automatically opens when the disk is inserted into the disk drive. The micro disk also has a write-protected notch at one of its corners. A write protected-notch is a small opening that has a tab you slides to cover the notch. If the write protected-notch is opened, the floppy drive cannot write data on the disk. However, in this case data can be read only from the disk. To write data on the disk, the write protected-notch must be closed.

Floppy Disk Drives

Floppy disk drive is a hardware component used to write and read data to and from the floppy disk. Personal computers and laptop computers have a floppy disk drive installed inside the system unit. Some computers use external floppy disk drive, in which the drive is a separate device with a cable that plugs into a port on the system unit. If a computer has one floppy disk drive, it is named as drive A (In case of two Floppy drives, one is named as drive A and second as drive B) by operating system. Most standard floppy disks today are high density. The computer must have the high-density floppy disk drive to access the high-density disks. The high-density disk drive can also access the lower density disks.

The floppy disk drive includes a motor that rotates the disk on a spindle. It also contains write/read head that writes and reads data to and from the disk when disk rotates. The floppy disk rotates at approximately 300 revolutions per minute. Most floppy disk drives have light emitting diodes (LED) that emits light when drive is accessing the floppy disk. You should not remove a floppy disk when the LED is on.

Zip Disk :

A Zip disk is a type of portable magnetic media. Its storage capacity is about from 100 MB to 800 MB. It is used to back up important data. ZIP disk is similar to floppy disk but its storage capacity is about 100 (or more) times greater than floppy disk. It is also more reliable storage medium than floppy disk. Like floppy disk, the data can be easily transferred from one computer to another by using Zip disk.

A Zip disk drive is used to write and read data to and from the Zip disk. The Zip disk drive cannot read data from floppy disk. It is not commonly used in personal computers. Most of the users use the external Zip drive, which can be connected to the USB port or parallel port on the system unit to write and read data to and from the Zip disk.

Storage Devices

Storage Devices - Data Storage Device - Data Storage - Computer Hard Drive - Storage - Storage Network - Data Backup

The main memory or RAM of the computer is volatile. It cannot be used as permanent storage because when computer is switched off, its contents are erased. Its storage capacity is also very small.

Storage devices are used to store data and programs permanently on storage media. A storage device is a computer hardware component that writes and reads data to and from storage media. Writing data means recording data from memory to a storage medium. Reading or retrieving data means transferring data from storage medium into the computer’s memory for use by the operating system or application program. When storage device writes data (or programs) on the storage medium, it performs function as output device. Similarly, when storage device reads data from disk and loads it into RAM, it performs function as input device. It is because; storage devices are also referred to as I/O storage devices.

The speed of storage device and memory is defined by access time. The access time of storage device is measured as the amount of time that a storage device takes to locate and retrieve a specific data on the storage medium. Similarly, the access time of RAM is measured as the time required delivering data from RAM to the processor. The access time of storage device is slower than access time of memory.

A storage media is the physical material on which data and programs are stored. It is non-volatile and is used to store information permanently for future use. The storage capacity of storage media is the number of bytes the storage media can hold. A large amount of data and programs can be stored on it. Its storage capacity is up to Gigabytes (GB) for personal computers. For example, a typical hard disk has storage capacity of 160 GB (approximately 80 billion bytes) or more. The application software and system software are stored on the secondary storage. Examples of secondary storage are floppy disk, Zip disk, hard disk, magnetic tape, CDs and DVDs.

What is Hard Disk

What is Hard Disk - Boot Disk - External Hard Drive - Hard Drives - Hard Drive- Hard Disk - Network Storage - Platter

Today, hard disk is most commonly used storage device in personal computers and laptop computers. Most application programs and operating systems require hard disk for installation and operation. A hard disk, also called a hard disk drive. It contains one or more metal platters mounted on a central spindle, like a stack of rigid diskettes. A hard disk is actually, a stack of platters. Each platter is coated on both sides with magnetic material. Both surfaces of each disk or platter are used to store information except for the top and bottom platters.

The hard disk and drive is a single unit. It includes the hard disk, the motor that rotates the platters. Each platter has two read/write heads, one for each side. The hard disk has also arms that move the read/write heads to the proper location on the platter to read or write data. The entire unit is enclosed in an airtight, sealed case. The hard disk is not portable. It is permanently fixed with the system unit. It is because hard disk is also referred to as fixed disk.

A disk or plotter has a flat circular shape. The surface of the disk is logically divided into circular tracks, which are subdivided into sectors. The set of tracks of different platters that are at a particular head position is referred to as cylinder.

However, the basic storage unit is sector. All sectors contained the same number of bytes. Usually, in a single sector 512 bytes are stored. The total capacity of a disk can be calculated by multiplying together, the following:

• Number of cylinders, which is the same as the number of tracks per surface.
• Number of read/write heads.
• Number of sectors per track.
• Number of bytes per sector.  

Today, the storage capacity of hard disk in PCs is from 40 GB to 160 GB (or more). The storage capacity of hard disk is determined from the number of platters it contains and their density. A plotter is made of aluminum, glass, or ceramic and is coated with an alloy material that allows storing data magnetically on the disk’s surface. Like floppy disk, hard disk is formatted before to store data on it. The operating system makes logical tracks on both sides of each platter and divides each track into sectors. Each platter of hard disk has a very high density. A large number of tracks are made on each surface of the platter.

Today, the storage capacity of hard disk in PCs is from 40 GB to 160 GB (or more). The storage capacity of hard disk is determined from the number of platters it contains and their density. A plotter is made of aluminum, glass, or ceramic and is coated with an alloy material that allows storing data magnetically on the disk’s surface. Like floppy disk, hard disk is formatted before to store data on it. The operating system makes logical tracks on both sides of each platter and divides each track into sectors. Each platter of hard disk has a very high density. A large number of tracks are made on each surface of the platter.

Hard Disk Performance :

The performance of the hard disk depends on the following factors.

1. Seek Time

Seek time is the time required to move a read/write head to a particular cylinder or track. Seek time is variable, because it will take more time to reach track 300 from track 1 than to reach track 100. Therefore, seek time is expressed as average seek time.

2. Rotational Latency

Once a cylinder or track is selected, the disk controller waits until the read/write head reaches to an appropriate sector. The time required to reach the head at the beginning of an appropriate sector is called rotational latency or rotational delay.

3. Transfer Time

Transfer time is the time required to transfer data, read from the disk into main memory. Alternatively, it is the time required to write data on the disk from main memory.

4. Assess Time

Access time is the sum of seek time, rotational delay and transfer time.

Mathematically it is written as;

Access time = Average Seek Time + Rotational Latency + Transfer Time

Once the read/write head is in position, the read or write operation is performed. Typically, a disk can transfer several megabytes of data per second. Therefore, the value of seek time and rotational latency is in milliseconds.

Optical Storage Devices

Optical Storage Devices - CD DVD Burner -Computer Hard Drive - Data Recovery - Storage Devices - CD Rom - DVD CD - DVD Storage - CD Rewritable - CD R - CD RW 

Today, the most widely used and reliable storage devices are the optical storage devices. These devices use laser technology to store and read data to and from the disk. The most popular optical storage devices are: CD-ROM drive, DVD-ROM drive, CD-Recordable drive, CD- Rewritable drive etc. Today, all PCs also contain one CD-ROM drive. These devices use laser light to write/read data to and from the optical storage media such as CDs (compact disks). A large amount oil data, software, movies and songs etc. can be stored on a single CD. Some optical storage media is read-only while others are read and write.

An optical storage media consists of a flat, round, portable metal disc, which is coated with a thin metal or plastic or other material that is highly reflective. These discs usually are 0.75 inches in diameter and less than one-twentieth of an inch thick.

The information on the optical disk is stored in the form of pits and lands. The pits are the tiny reflective bumps that are created with laser beam. The lands are flat areas separating the pits. A land reflects the laser light, which is read as binary digit 1. A pit absorbs or scatters light, which is read as binary digit 0. The high-powered laser beam creates the pits. A lower-powered laser light reads data from the disc. Like tracks on a magnetic disk, the tracks of an optical disk are divided into sectors but shape of these sectors is different than sectors of magnetic disk.

The operating system assigns a letter to the optical storage devices that come after all the hard disks and other portable disks. For example, if a computer has one floppy drive, one hard disk, one Zip disk drive and one CD-ROM drive then letters assigned to drives will be as under:

'A' for floppy disk drive

'C' for Hard disk drive

'D' for zip disk drive

'E' for CD-ROM drive

CD-ROM

CD-ROM stands for Compact Disc Read-Only-Memory. CD-ROM is a type of optical disc that uses laser technology to store and to read data to and from the disc. A large amount of data can be stored on a single disk. Once the information is stored on the CD-ROM, it becomes permanent and cannot be changed (altered). The information can only be read for processing. Therefore, it is called Compact Disc Read Only Memory.

Now-a-days CDs are commonly used in personal computers. The CD-ROM is removable and can be used to transfer data from one computer to another like a floppy disk. The storage capacity of CD-ROM is 1000 times greater than floppy disk. A typical CD-ROM has storage capacity from 650 MD to 1GB. Today, most of the software are available on the CDs. The software companies distribute their products on the CDs. For example Microsoft Office is available on one or two CDs. Similarly, Windows operating system is also available on one CD.

CD-ROM drive 

The CD-ROM drive is used with computer to read the information from the CD-ROM. The data transfer rate of first CD-ROM used with computer was 150 KBps (Kilobytes per second). It was known as single speed drive and is denoted by X. This rate is much slower than that of a typical hard disk drive that reads data at a rate of 5 to 15 MBps (megabytes per second). Manufacturers measure the speed of all CDROM drive relative to the first CD-ROM drive. Today, CD-ROM drives have transfer rates (or speeds) ranging from 48X to 75X or more. For example, a 48X CD-ROM drive has a data transfer rate of 7,200KBps (i.e. 48 x 150 = 7200) or 7.2 MBps. It. means that the higher the number, the faster the CD-ROM drive. However, the faster CD-ROM drives are more expensive.

DVD-ROM

DVD stands, for Digital Video Disc or Digital Versatile Disc. DVD-ROM is an extremely high capacity optical disc with storage capacity from 4.7 GB to 17 GB. DVD disc is specially used to store movie films. It is also used to store huge databases, music, complex software etc.

The latest generation of DVD-ROM disks actually uses layers of data tracks; it is because the storage capacity of DVD-ROM is very high. The DVD-ROM drive or DYD player reads data from the first layer, and then look through it to read data from second layer and so on.Some DVD-ROMs are double sided. It means data is stored on both sides of the disc. A DVD-ROM looks like a CD-ROM. Although the size and shape is similar to CD-ROM but DVD-ROM stores information in different manner A DVD-ROM drive can read ordinary CD-ROM disks.

CD-R

CD-R stands for Compact Disc Recordable. It is a blank disk that is used to store information. The user can also write data on an optical disc. The process of writing data on the optical disc is called burning. A locally developed CD-R can be used in any CD-ROM drive. A CD-R is functionally equivalent to a pre-recorded CDROM. Mostly the users use the CD-R to store their valuable data and software. It must be noted that once data is written on the CD-R. It cannot be changed. However, you can store data on other part of the disk until it is full. Each part of a CD-R can be written only one time and can be read as many times. Many utility programs are available to write data on CD-R but the most popular and commonly used software for personal computers is "Nero Burning ROM". Windows has its own built-in software to write data on CD-R.

Today most of the important data is backed up on the CD-R and it is the most reliable medium. The CD-writer is used to write data on CD-R.

The main disadvantage of CD-R is that information can be written only once. These cannot be overwritten and erased. The CD-ROM is also slow in accessing as compare to hard disk.

CD-Writer

A CD-writer or recorder (or simply CD-R drive) is used to write data on CDR disks. Usually, a CD-writer can read information from CD as well as write information on CD. The locally produced CD-R disks are created with CD Writers. Today, most of the PCs have CD writer.

The speed of these drives is up to 48X or more. These drives are more expensive than ordinary CD-ROM.

CD-RW

CD-RW stands for compact Disc Rewritable. The CD-RW is a new generation of optical disk. It is erasable disc. The user can write and over-write data on the CD-RW disc many times. The CD-RW disc is also referred to as erasable CD (or CD-E). The CD-RW acts like a floppy and hard disk that allow users to write and re-write data. However, the reliability of the disc tends to decrease, each time you rewrite data.

Both CD-R and CD-RW are used for taking backup of important data from a hard disk. These are also used to create audio CDs. For example, you can record your own music or movies from purchased CDs.

CD-RW Drive

You must have a CD-RW drive to write data on the CD-RW. These drives have read and write speed is up to 48X or more but the re-write speed is 10x or more. The CD-RW drive is advanced and more expensive than CD-R drive. It can write data on both CD-R and CD-RW discs and also can read data from them. Today, most of the PCs have CD-RW drive.

Mobile Storage Devices

Mobile Storage Devices - Smart Card Reader - Smart Card - Data Storage - Flash Memory - Compact Flash - Memory Cards - Card Memory - Storage - Flash Drives

There are numerous types of mobile storage devices. The most important ones are:

1. Online Storage
2. Smart Cards
3. Flash Memory Devices   

1. Online Storage

Online storage is a website on the Internet that offers the storage of data for free of cost or against some payment through credit card. The capacity of storage depends upon the packages offered by the website owner. Through the website, data is stored on a computer which remains online 24 hours a day and 7 days a week.When you connect to the website, you can browse through your allocated memory space just as you browse with the help of Windows Explorer on your personal computer. Thus you can access your data/information wherever you travel throughout the world. National or international travelers having laptops or handheld computers mostly enjoy the online storage facilities. Many companies offer online storage facilities but www.webdepositbox.com is a famous online storage service that allows users to store, access, and organize files.

2. Smart Cards

A smart card is a small card normally of the size of credit card or ATM card. Thus you can store data/information in the card and sometimes miner processing of data/information can also be made by its built-in microprocessor. In order to read and write data on a smart card, you need a special device called smart card reader.

There are two types of smart cards:

1. Intelligent Smart card
2. Memory Smart card

An Intelligent Smart card contains a built-in microprocessor and has input, processing, output, and storage facilities. Whereas a Memory Smart card gives only data storage facility. Many digital cameras, laptops and handheld computers nowadays use smart cards.

3. Flash Memory Devices

Flash memory is a type of non-volatile memory that can be erased electronically and reprogrammed, similar to EEPROM. Most of the PCs also use flash memory to hold their startup instructions.

Flash memory is also known as Flash ROM. The Flash memory is used to upgrade I/O devices by upgrading the new software purchased from market into the Flash memory. The early I/O devices were upgraded by replacing the old circuit board or chip with a new one. It was a time consuming and costly method. The Flash memory solves this problem of the user. When new hardware devices are added to the computer, the information about devices are configured and stored in the flash memory. It is available in size up to 512MB. It does not require a battery to maintain its contents. It is more expensive than the hard disk storage.

Flash memory chips are also used in mobile computers and devices to store data and programs. For example, these are used in PDAs, digital cellular telephones, set-top boxes, digital voice recorders, pagers etc. When you enter names and addresses into PDAs, a flash memory chip stores the data. The flash memory chip in a digital cellular telephone stores names and telephone numbers. The flash memory is also used in digital camera. When we take pictures with digital camera, these are stored in a flash memory rather than on photographic film.