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Home , Computer memory, Floppy disk, Hard disk drive

Computer Memory

Mathematics Department 1 Hardware –Input devices –Output devices –Main memory –Secondary storage devices

Slide 1- 2 –Input devices –Output devices –Main memory –Secondary storage devices

Slide 1- 3 MAIN MEMORY

(अथिर )

Contents of RAM are lost Contents retained while when power is turned off power is off

Mathematics Department 4 MAIN MEMORY

(अथिर )

Contents of RAM are lost Contents retained while when power is turned off power is off

Mathematics Department 5

Mathematics Department 6 • RAM is a volatile (अथिर ) • It is non-volatile • Contents of RAM are lost • Once the prog are written when power is turned off it cannot be changed and remain intact even if power • Both the read and write is switched off. operations can be • Read only . User cannot performed make any changes.

• RAM memory is only • ROM memory is used to used to store the store permanent temporary information. information and cannot be deleted. - • Store information • Store the programming of the programs for needed to begin the currently running boot up or start on the computer the computer • Types of RAM • Types of ROM Static dynamic RAM. RAM PROM, EPROM EEPROM.. • The price of RAMs The price of ROMs are • are high low • Physically size of Physically size of ROM chip RAM chip is larger is smaller than RAM chip. than ROM chip Mathematics Department 8

Types of RAM

DRAM requires a single • Static RAM • and a transistor (SRAM) does due to the use of not need to be refreshed , DRAM requires to be refreshed SRAM,

periodically which uses six

they will lose their• transistors , contents. slower, and can hold cheaper, larger capacity its contents longer.

. 3. Another type of RAM, called , can store its contents after power is turned off. Flash memory is used in digital cameras to store pictures

Mathematics Department 10 • PROM Programmable Read Only Memory (PROM). • You know that it is not possible to modify or erase programs stored in ROM, but it is possible for you to store your program in PROM chip. Once the programmes are written it cannot be changed and remain intact even if power is switched off. • Programs or instructions written in PROM or ROM cannot be erased or changed.

Mathematics Department 11 • EPROM: Erasable Programmable Read Only Memory, which over come the problem of PROM & ROM.

• EPROM chip can be programmed time and again by erasing the information stored earlier in it.

• When the EPROM is in use information can only be read.

Mathematics Department 12 auxiliary memory or secondary storage

• 1-Hard Disk, in computer science, one or more inflexible platters coated with material that allows the magnetic recording of computer . • Hard disks provide faster access to data than floppy disks and are capable of storing much more information. Because platters are rigid, they can be stacked so that one hard-disk drive can access more than one platter. • Most hard disks have from two to eight platters.

Mathematics Department 13 • : Magnetic tapes are used for large like mainframe computers where large of data is stored for a longer time • : It is similar to magnetic disk discussed above. They are 5.25 or 3.5 inch in diameter. They come in single or double density and recorded on one or both surface of the diskette. The capacity of a 5.25- inch floppy is 1.2 mega whereas for 3.5 inch floppy it is 1.44 mega bytes.

Mathematics Department 14 • floppy disk * small magnetic disk: a small flexible magnetically coated disk in a rigid plastic case on which data can be stored or retrieved by a computer

* a regular floppy disk holds approximately 1.44 .

Mathematics Department 15 CD- ROM • CD-ROM, short for read-only memory, a rigid plastic disk that stores a large amount of data through the use of laser optics technology. • Because they store data optically, CD-ROMs have a much higher memory capacity than computer disks that store data magnetically. • However, CD-ROM drives, the devices used to access information on CD-ROMs, can only read information from the disc, not write to it. • CD-ROMs can store large amounts of data and so are popular for storing and multimedia material. The most common of CD-ROM holds approximately 630 megabytes .

Mathematics Department 16