The storage devices are one of the most important components of the computer system. They are the data storage devices that are used to store the data. The computer has many types of data storage devices. Some of them can be classified as the removable data Storage Devices and the others as the non removable data Storage Devices. The memory is of two types; one is the primary memory and the other one is the secondary memory. The primary memory is the volatile memory and the secondary memory is the non volatile memory. The volatile memory is the kind of the memory that is erasable and the non volatile memory is the one where in the contents cannot be erased. The secondary memory is used to store the data permanently in the computer. The secondary storage devices are usually as follows: hard disk drives – this is the most common type of storage device. The other ones include the floppy disk drives, the CD ROM, and the DVD ROM. The flash memory, the USB data card etc.
RAM (random access memory), : RAM is called as primary memory which locates the operating system, application programs, and data in current use so that the computer's processor reaches them quickly. RAM is called "random access" because any storage location can be accessed randomly or directly. RAM is much faster than the hard disk; the floppy disk and the CD-ROM. RAM can be taken as short-term memory and the hard disk as the long-term memory of a computer. However, RAM might get slow when used to its limit
Hard disk drive: The hard drive, also called the hard disk or fixed disk, is the primary storage unit of the computer. It is always labeled the C drive. Additional drives are labeled after it as the D, E, F, etc. It has several read/write heads that read and record data magnetically on platters, a stack of rotating disks inside the hard drive. Hard drive is important for the following reasons:
It stores programs that must be installed to the hard drive before they can be used.
It stores data files that can be accessed later.
It organizes files like a file cabinet so they can be accessed more easily.
The Hard Drive can store a large amount of computer data on it. Much advancement has made it possible to store large amounts of data in a small space. The hard drive's speed is discussed in terms of access time. This is the speed at which the hard drive finds data. The average access time is measured in milliseconds. One millisecond equals 1/1000 of a second. The average drives had 9 to 14 ms access time. The lower the access time, the faster the hard drive. The capacity or amount of information that a hard drive can store, is measured in bytes.
Basically there are three types of Hard Drive Connections: (1) Integrated Device Electronics (IDE) (2) Small Computer Interface (SCSI) (3) Enhanced Integrated Drive Electronics (EIDE)
Optical disk drives
Optical disk drives including the compact disk-ROM (CD-ROM), CD-Recordable (CR-R), CD-Rewriteable (CD-RW) and the Digital Versatile Disk drives (DVD) are also key storage devices.
A Compact Disk (CD) is a small medium that can store data pertaining to audio, video, text, and other information in digital form. Initially, CDs were read-only, but newer technology allows users to record as well. To record data into a CD, you need a CD recorder. Normally this type of CD is either CD- Recordable (CD-R) or CD-Rewritable (CD-RW) . The latter can be used again and again by erasing the data where as in the CD-R, once the data recording is completed, it becomes a CD-ROM and nothing can be deleted. CD-ROM (Compact Disc, read-only memory) can store computer data in the form of text, graphics and sound.
For batch production purposes CD-Copiers are used for copying and labelling of 50 CDs at once. CD-ROM drives store up to 660Mbyte at access speeds of upto 7200Kbits per second.
Generally CDs are all based on a particular CD standard named after the colour of its covers.
The original audio CD was based on the yellow book standard,
The CD-ROM on the red book but is also compatible with the yellow book standard so you can listen to audio CDs on your computer.
CD-R and CD-RW are based on the orange book standard.
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