MEMORY

BASICS OF MEMORY It is a place to store data & sometimes called storage. Basic unit of storage is flip flop(FF). FF stores 1 bit of data. Storage can be collection of FF to form registers(ex. Base and limit registers). Order of amount of data storage:-FF<Memory cell <IC’S. Volatile memory:-Memory in which data is stored until we off the power supply. Non volatile memory:-Memory in which data is still stored after power supply is off.

Types of Memory 1) On the basis of type of data stored :- 1.1)programs. 1.2)other personal data. 2) On the basis of accessibility of data :- 2.1) Random access memory. ex) RAM, Hard disk drive(HDD). 2.2) Sequential access memory :- ex) Floppy drives, Magnetic tapes. 3) Traditional division :- Primary, Secondary & Tertiary.

3. 1)Primary Memory(PM):- In this data is directly accessible to CPU 3.1)Primary Memory(PM):- In this data is directly accessible to CPU. ex.) RAM, ROM etc. 3.2)Secondary Memory(SM):-Data is not directly accessible to CPU. The CPU usually uses its input/output channels to access secondary storage. ex.) Hard disk drive, floppy, magnetic tapes etc. 3.3)Tertiary Memory(TM) :-Used to store huge amount of data. It has various racks to store data. It contain various tape drives. For accessing data from it computer needs to copy data to secondary memory first. Its data accessibility slower than SM. ex.) Tape libraries etc.

RAM Full form :-Random Access Memory. It is a volatile memory. Used for temporary storage. Available range in market is 256 MB-8 GB. TYPES OF RAM :- SRAM(Static RAM) & DRAM(Dynamic RAM). History of RAM.

SRAM DRAM 1)Data is stored as long as power supply supplied. 2)Contains FF’S, transistors, MOS (Metal Oxide Semiconductor). 3)Used large no. of transistors. 4)costly. 5) Less time required to access data. 6)No capacitor used so data stored as long as power supply given. 1)Data is stored as long as capacitor is charged. 2)Contains FF’S, transistors, MOS, capacitor. 3)Used comparatively low no. of transistor. 4)Cheaper. 5)Comparatively more time required to access data. 6)Need periodic refreshing of memory so that capacitor get charged.

ROM Full form :-Read Only Memory. Non volatile memory. Used to mainly store programs. Types Of ROM:- Mask programming:- In this programs are stored by manufacturer in the memory. PROM(Programmable ROM):- In this user is free to store programs in the memory. EPROM(Erasable PROM):-In this stored programs can be erased by using UV rays. EEPROM(Electrically EPROM):- In this programs can be erased electrically.

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