SECONDARY MEMORY

CD-ROM and DVD-ROM
CD (Compact Disc) and DVD (Digital Video Disc) is now commonly used throughout the world because it is standard equipment that can be relied upon. CDs can be easily carried and can even to save the data. In general, the notion of a CD-ROM (Compact Disc Read Only Memory) is a medium for storing data or other information in a very large amount of more than 600 MB. Much greater if we compare it with the floppy disk (1.4 MB). CD ROM can be accessed and read on the screen, or printed from any computer with a CD-ROM player. CDs can store information in various forms, such as: text, images, presentations, slides, audio and video.

Materials CD-ROM maker
CD-ROM is now generally made of resin (polycarbonate) and coated with highly reflective surfaces such as aluminum. Information digitally recorded as microscopic pits on a reflective surface. This process is done by using high-intensity laser. A perforated surface is then coated by a layer of clear. The information is read using low-intensity laser that illuminates the translucent layers rotate while the motor drive. Laser intensity was changed after the holes are then reflected and detected by fotosensor which is then converted into digital data. Writing data on CD-ROM can only be done once. However, the optical disk has advantages in terms of mobility. Its small and thin it easy to carry anywhere.

Types of disc :

Disc which we often see in the market is divided into three namely:

1. CD-ROM

Usually the CD-ROM discs silver. Manufacturing process is by putting a layer of plastic that has been illuminated by a laser beam. The laser beam will form a pit (hole) micro-sized, very small. The holes will form a line of code in the form of data content. Once a hole is created, it can not be closed again. Then the plastic layer will be covered again by the liquid plastic that is useful as a protector and reflectors. All that the process is carried out gradually in a printing machine. Tools CD-ROM mold looks like a cookie cutter analogy martabak making sweet and also very similar. As the name implies ROM (Read Only Memory), the data in the CD-ROM can not be deleted so that the CD-ROM can not be erased or recorded on a CD Writer tool we used to have. CD-ROM quality is determined by the three layers as shown. Reflector layer must be able to reflect light emitted by a laser beam to perfect that there is information that can read data dilapisan well. While the protective layer must be strong so that the data layer is not damaged by scratches or dirty. Original CD-ROM are generally more durable than the pirated CD-ROM. Because the quality of the layers of the original CD-ROM is very strong and qualified under the standards of reliable quality. However, not closed the possibility of some pirated CD-ROMs that berkualias, but the price is not cheap.

2. CD-R

Stands for Compact Disc Recordable. This dish is generally green, but there is a blue, red and black. Manufacturing process is similar to CD-ROM, by the way and put a layer of plastic. The difference is the plastic that was not illuminated by a laser. Then the plastic layer will be covered again by the liquid plastic that is useful as a protector and reflectors. The plastic sheets will be illuminated by a laser at the moment we want to record it. That's why CR is also a CD-Blank because it is still empty. Determining the quality of the CD-R is also equal to the quality of the CD-ROM. But there should be extra attention, that is because the recording process performed after the CD was printed and there are so many CD-R sold in the market, the quality of the sheet in the CD-R's must match the CD Writernya.

3. CD-RW

CD-RW, which stands for Compact Disc Rewritable CD is a type of content that we can own, then we can delete it if desired. CD-RW prices are usually more expensive than CD-R.

DISKETTE

Floppy disk storage medium which is very popular for personal computers. Physically, the disks are made of plastic plates in which circular on its surface is coated by a magnet as a place to store the data stroke-stroke. To keep the data or programs stored in fixed disk clean up, diskettes and then wrapped in a cardboard square.

To do the reading or writing, diskette must be inserted into a drive, the drive is then referred to as disk-drives. At each drive that is, already contains a shaft and a drive motor which functions to rotate the discs with a speed of about 360 to 500 rpm. An electronic signal coming from the control system, will cause the read / write head that serves to do the reading / writing to continue to move over the surface of a spinning disk to do the reading / writing.

The parts of the disk are:

Stress relief cutouts:

Serves to open / close hook drive. Read / Write Windows, a window that is used to read and write from the drive mechanism.

Hub ring :

Serves as a handle to rotate the disks.

Index Hole :

Where there are holes in the cardboard yag / cover accumulated with holes on the disk, indicating the position of sector 0.

Write

This hole when in the open position, the disks can be read and written; When closed the disc can only be read alone.

Label 

Used to write the name of the owner or the name of the program disk / data stored therein.

The place is in the disk is divided into several tracks, and each track will be divided into several sector. Constitutes the smallest sector where data is stored. In this case, each sector can accommodate up to 256 Charakter. Each sector is always characterized by a sector address, so that the read / write head can quickly find the data in question. Number of sectors per track is not the same, depending on the type of computer used. New diskette must be formatted first and can be used. of this format, will produce a number of organized sector in order, so that the read / write head can find data stored. In addition, the users are also able to predict the data to be stored. Physically, the disk has a size: 8 inches, 5:25 inches and 3.5 inches, though, the capacity of floppy disks is not measured physically. Disk capacity can be seen from the label is written, for example: DD (Double Density), for the 5:25-inch floppy disks have a capacity of 360 KB, and 3:50-inch diskettes have a capacity of 720. Diskette with the label HD (High Density) to 5:25-inch size 1.2 MB capacity, and 3:50 to dikset inch 1.4 MB capacity. In addition, 3:50-inch floppy disk size is labeled ED (Enchanced High Density), has a capacity of 2.8 MB, but not commonly used. Understanding density can be interpreted as the density in the data store, so the higher the density, which is owned by a diskette, then the capacity it has also higher. Because the data stored in the form of scratch-scratch magnetic disks to be treated carefully. Diskette must be protected from heat, magnets, arches, direct touch, dirt or the writing of a label directly by using the tools sharp / pointed.

HARDDISK

Hard disk is a data storage medium that is quite popular for the mainframe or the PC. Disk is a storage medium that has a different physical form compared with the floppy. In general, hard disks are usually installed and integrated in the CPU (fixed disk). Mechanism that causes the stored data can be read or written in the hard disk, called a disk drive. In the hard disk are metal plates arranged circular layers, and there is a metal plate motor and read / write head of his. Advantage of the hard disk is able to accommodate the data in very large quantities and have the speed at the time recall stored data. Hard drive with 3 Giga Byte size at this time was considered too small, and now began to circulate hard drive with a size much larger. In its usage within the PC, the hard disk requires an additional card contained in the computer and serves as a working controller from the hard disk. In the disk-drive, there is a device capable of rotating players until 3500 rpm or more. Read / Write Head that there will ditumpu with an arm that always move to explore the entire surface of the hard-disk to detect or perform writing / reading data. The combination of hard-disk rotation and arm movement is able to determine the position of each track that is inside the hard-disk. Types of hard disk that uses a single disc, but some are using multiple disks packaged in a form (disk-pack). Disk-pack also has a fixed type (fixed) and removable (can be moved). Read / Write heads are owned by the disk-pack is more than one, which is in accordance with the number of discs that have. Layer the top and bottom, usually only used as a protective cover and ill-used to write data. Computer programs on a PC that was popular at the moment, such as Microsoft Windows, Office, Netscape Communicator, and others again, in need of hard-disk facility with a capacity large enough to accommodate and run programs there. Western Digital Protege currently produces hard disk with 5400 rpm speed of play. Latest draft of this WD hard drive makes physical protection from things that do not want a way to hide electrical elements at the bottom of the hard disk. Owned capacity is 20 GB, with transfer speeds of 90 MB / second. Hard disk must be treated carefully, because very sensitive to dust, smoke or fingerprints can sometimes attached dipermukaannya, where it could damage the data stored therein.