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STORAGE DEVICE A storage device is any computing hardware, that is used for storing and managing data for later use. Purpose of storage Many different forms of storage, based on various natural phenomena, have _ been invented. So far, no practical universal storage medium exists, and all forms of storage have some drawbacks. Therefore a computer system usually contains several kinds of storage, each with an individual purpose. History 1928- magnetic tape - fritz pfleumer 1932- magnetic drum - G Taushek 1946- Williams tube - prof. Tredrick C Willam memory technology mostly permitted a capacity of a few bytes. The first electronic programmable digital computer, the ENIAC, using thousands of octal-base radio vacuum tubes, could perform simple calculations involving 20 numbers of ten decimal digits which were held in the vacuum tube accumulators. 1956- Hard disk 1963- Music tape 1966- DRAM 1980- CD philips Robert H Dennard James T Russel Introduction to Memory “+ In computing, memory refers to the physical devices used to store programs (sequences of instructions) or data (e.g. program state information) on a temporary or permanent basis for use _ in a computer or other digital electronic device. “+ The term primary memory is used for the information in physical systems which are fast (i.e. RAM), as a distinction from secondary memory, which are physical devices for program and data storage which are slow to access but offer higher memory capacity. “+ Primary memory stored on secondary memory is called "virtual memory". Memory is of two types:- 1. Primary memory (RAM,ROM,CACHE,FLASH) 2. Secondary memory (FLOPPY DISK,MAGNETIC DISK,MAGNETIC TAPES,OPTICAL DISKS) READ ONLY MEMORY (ROM) The acronym for ROM is Read Only Memory when the data is burnt on a ROM, it cannot be removed nor it cannot be altered it can only read . ROM is known as nonvolatile. ROM stores programs such as the program that boots the computer. ROMs are widely used in calculators and other devices such as laser printers. il TYPES OF ROM There are five basic ROM types:- 1. Masked ROM (READ ONLY MEMORY) 2. PROM (PROGRAMMABLE ROM) 3. EPROM (Erasable Programmable ROM) 4. EEPROM (Electrically erasable programmable ROM) 5. FLASH MEMORY(ONE KINDS OF cc Psa | PROM: « It is an another type of primary memory in computer, which is called Programmable Read Only Memory (PROM).It si not possible to modify or erase programs stored in ROM,but is possible for you to store your program in PROM. Once the programmers, are written it cannot be changed and remain intact even if power is switched off. EPROM: The Erasable PROM chip allows the stored data to erased and new data can be reprogrammed. Information store in EPROM exposing the chip for some time ultraviolet light and it erases chip is reprogrammed using a special programming facility. When the EPROM is in use information can only be read. The advantages of ROM are They are non-volatile They are cheaper than RAM They are static and do not refreshing They are more reliable than RAM as their circuit is simple. They are available in longer sizes than RAM. They are easier to interface than RAM. CACHE :- A small memory chip is attached between CPU and main memory , whose access time is very close to the processing speed of CPU .It is called cache memory. Its physical location is in CPU and is much faster than RAM. Its size is normally small. We can see the cache memory of CPU in BIOS setup. FLASH MEMORY The flash memory is a type of chip that is called as the EEPROM. BIOS of computer, the memory stick that is found in the digital cameras , USB pen drives , the memory cards of the mobiles etc are the example of flash memory. The important properties of the flash memory are that it is much fast and very much easier in use . Flash drive can be efficiently used for the purpose of a hard disk. Advantages of flash memory when used as a hard disk Advantage of the flash memory over the hard disk is that it is compact and much efficient for the data transfer. There are no mobile parts in it As in the hard disk there are the platters and the read write head moves over it. There is no such mechanical component in the flash memory drive. Hence it is a purely electronic device. The flash memory is quite expensive as compared to the hard disk drive, but it is light in weight 
