Wednesday, 2 December 2015

COMPUTER MEMORY : COMPLETE NOTES

Computer memory refers to the hardware device that are used to store and access data or programs on a temporary or permanent basis.

There are TWO TYPE of nature of memory in a computer.
(1) Temporary/ Volatile
(2) Permanent / Nonvolatile

PRIMARY MEMORY
It is computer memory that a processor or computer accesses first or directly.
 
NOTE
Primary memory also known as main memory.
Secondary Memory also known as Auxiliary memory or Non Volatile Memory.

RAM (RANDOM ACCESS MEMORY)
When you power off your computer the data stored in RAM is deleted, means volatile in nature.
 
Static RAM (Static Random Access Memory)
It is called static because it will continue to hold information without refreshment. SRAM use 28 pin system.
Dynamic RAM
It requires refreshment. Example of dynamic ram are DDR1, DDR2 ,DDR3, DDR4.

VRAM
Video RAM, also known as multiport dynamic random access memory (MPDRAM), is a type of RAM used specifically for video adapters or 3-D accelerators.

Cache memory
A cache used by the CPU to reduce the average time to access memory.It is used in between the main memory and CPU.

ROM (Read Only Memory)
ROM is also a type of non-volatile storage which is located on the motherboard that contains the basic instructions for what needs to happen when a computer is powered on.

PROM
Programmable read-only memory (PROM) is read-only memory ( ROM ) that can be modified once by a user.

EPROM
Acronym for erasable programmable read-only memory, EPROM is a special type of memory that retains its contents until it is exposed to ultraviolet light.

EEPROM
Short for electrically erasable programmable read-only memory. EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge.

SECONDARY STORAGE
It is used to store data for backup purpose.
Types of access:
(I) Sequential access
(II) Direct/Random access
 
Magnetic Tape
It is based on sequential access.
 
MAGNETIC DISK
->>HARD DISK
It is a permanent magnetic storage device.


->>FLOPPY
It is known as diskette

->>Zip Disk
A zip disk is like a large, chunky floppy disk. It can store 750MB data.

OPTICAL DISC
Optical storage refers to the storage of data on an optically readable medium by laser beam.

CD (COMPACT DISC)
CD is made polycarbonate plastic material and aluminium coated. CDs have a capacity of about 700MB.
 
DVD (Digital Versatile Disc)
It is an optical disc like the CD, but with much higher capacity.
DVD can store about 4.7GB.
 
BRD (Blue Ray Disc)
Blu-ray Disc is a high-density optical disc format similar to DVD .It’s capacity is up to 50GB to 100 GB.
 
HVD (Holographic Versatile Disc)
The Holographic Versatile Disc (HVD) is an optical disc technology It’s capacity is 6 TB.

Flash memory
Flash memory is an electronic non-volatile computer.
Ex Pen drive, memory card. Latest version of pen drive is 3.1 and latest version of memory card is class 10 ultra.


Disk Structures
Track -The disk is divided into no. of concentric circles called tracks.
Sector -Data storage are in one track multiple block is called sector

Virtual Memory
Virtual memory combines your computer’s RAM with temporary space on your hard disk. It is also called Extended RAM.

NEW TECHNOLOGY STORAGE
DDR 4 RAM
It is a HIGH SPEED RAM developed by Samsung Its speed is 2133 to 4266 mt/s (million transfer per second) SK Hynix developed 128GB DDR4 RAM with High speed performance DDR4 RAM used 288 pins system.

SSD (SOLID STATE DRIVE)
Solid-state drives actually aren't hard drive in the traditional sense of the term. It is made by semiconductor chips.

3D X point memory
Intel and micron have unveiled 3D X Point a new memory technology 1000 time faster than NAND and 10 time faster conventional DRAM.

Important MCQs

Q.1Which computer memory is used for storing programs and data currently being processed by the CPU?
A) Mass memory
B) Internal memory
C) Non-volatile memory
D) PROM
E) None of these
 
Q.2) CD-ROM
A) Is a `semiconductor memory
B) Memory register
C) Magnetic memory
D) Optical storage
E) None of these
 
Q.3) A name or number used to identify a storage location is called
A) A byte
B) A record
C) An address
D) All of above
E) None of these

Q.4 The difference between memory and storage is that memory is …. And storage is …
A) Temporary, permanent
B) Permanent, temporary
C) Slow, fast
D) All of above
E) None of these
 
Q.5 Which of the following memories must be refreshed many times per second?
A) Static RAM 
B) Dynamic RAM 
C) EPROM 
D) ROM 
E) None of these
 
Q.6 Floppy disks which are made from flexible plastic material are also called? 
A) Hard disks 
B) High-density disks  
C) Diskettes 
D) Templates 
E) none of these
 
Q.7 Which of the following storage uses laser technology to store data?
A) Tape 
B) hard disk 
C) floppy  
D) CD 
E) none of these
 
Q.8 Which of the following magnetic disk is used in computer permanently?
A) Tape  
B) hard disk 
C) floppy 
D) CD 
E) none of these
 
Q.9 Virtual memory stores data in---------------?
A) Tape 
B) hard disk 
C) floppy 
D) CD 
E) none of these

Q.10 Which of the following memory is close to CPU
A) Virtual memory 
B) Main memory  
C) Cache 
D) Secondary memory 
E) none of these

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