Storage Devices

It is consist of primary and secondary memory.

Primary Storage Devices – It is internal storage and consists of cache, ROM & RAM.

RAM (Random Access Memory) – It is read/write volatile memory storing temporary data in MB.

ROM (Read Only Memory) – It stores data permanently which can only be read so it is non-volatile. It stores programs for booting the computer, like BIOS (Basic Input & Output System).

Cache – It is used for speeding up the data supply to CPU and stores frequently used data in KB.

Secondary Storage Devices – It is usually external storage and consists of tape, disk & flash.

Magnetic Tape – It is similar to an audiocassette having plastic strip for storage in a cartridge. It is slow in data access but, input and output speeds is high. Its capacity is up to 5120 GB.

Disk Drives – It is circular in shape having track and sectors. The disk surface is divided in concentric circles called tracks which are further subdivided into sectors. Greater the number of tracks so, more is the storage capacity of the disk.

Hard Disk Drive – It is used for mass storage with direct access. It is non-volatile in sizes like 3.5”, 5.5” and 8”. It has disk platters on a spindle, with read/write head having 250-1024 GB capacity.

Optical Disk – Laser beam burns disk surface to write and low power reflected beam to read. It has speed rating or data transfer speed where 1X refers to 150 Kbps. CD-ROM and DVD are examples with 700 MB and 4.3 GB capacity. Blue ray is upcoming technology with 50 GB data.

Flash Memory – It uses semiconductor memory and is used in USB drives, memory cards, etc.

Data can be read or written to it and device can be detached to transfer or move data.

Central Processing Unit (C.P.U) – It executes given commands and consist of

Control Unit – It supervises and controls information flow by a clock signal as per which the processing is done. Clock signal is given in MHz/GHz (Mega Hertz/ Giga Hertz).

Arithmetic Logic Unit – It performs arithmetic and logical operations on data from memory.

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