Auxillary and Secondary Storage Device

SECONDARY STORAGE DEVICES.

Although speed is still a very important criterion, the main objectives when dealing with secondary storage are data integrity and mass storage capability, coupled with low cost. Auxiliary, external, or backing store are alternative names for secondary storage.

Computers can save information permanently, after you turn them off. This way, you can save your work for future use, share information with others, or modify information already available. Secondary storage holds information external from the CPU. It allows you to store programs, such as Microsoft word and Micro soft Excel. It also allows you to store the data processed by programs, such as document file, text in MSWORD.

We described main memory in five. This is the internal and temporary storage of data and programs in the computer’s memory. Once the power is turned off or interrupted, everything in internal storage disappears. Such storage is therefore said to be volatile storage. Thus, we need external, more permanent or non volatile storage for data and programs. We also need external storage because users need much more capacity than is possessed by a computer’s primary memory.

Competent users need to be aware of  these secondary devices. Secondary storage devices are devices permanently hold data and information as well as programs. They include:

Floppy disk

 Hard disk

Optical disk

Magnetic disk

Flash disk

Magnetic tape

PROPERTIES OF  SECONDARY STORAGE DEVICES

1.  physical parts: Any secondary storage system involves two physical parts, a peripheral device and an input/output medium. A disk unit and tape unit are examples of peripheral devices; magnetic disk platters and magnetic tape cartridges are type of media. Data and programs are written onto and read from some type of medium. The medium must be situated on a peripheral device for the CPU to process its contents.

In most secondary storage systems, media must pass by a read/write head in the peripheral device to be read from or written to. For instance, when you play or record to a music tape on your home stereo system, the tape passes a head on the tape recorder, which will either play or record music . magnetic tapes on computer systems work by an identical principle. Magnetic disks also use read/write heads that perform similar types of reading and writing tasks.

2.  Non-volatility Property

Secondary storage media are non-volatile. This mean that when the power on the peripheral devices is shut off, the data stored on the medium remain there. This is in contrast to most types of memory, which are volatile. With volatile storage, the data on the medium disappear once the power is shut off.

3.  Removable versus Non removable Media.

In many secondary storage systems, although the peripheral device is online to the computer, the associated medium must be loaded into the device before the computer can read from or write to it. These are called REMOVABLE MEDIA secondary storage systems. Diskette, some types of hard disks, magnetic tape cartridges, magnetic tape reels, and optical disks are examples of removable media used on such systems. Other secondary storage systems, such as those that use Winchester disks are fixed-media secondary storage systems. A Winchester disk system, the disk is encased in a sealed unit within the peripheral device, and it cannot be conveniently removed.

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