вторник, 30 ноября 2010 г.

Random-access memory



Random-access memory (RAM) is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order (i.e., at random). "Random" refers to the idea that any piece of data can be returned in a constant time, regardless of its physical location and whether it is related to the previous piece of data.

The word "RAM" is often associated with volatile types of memory (such as DRAM memory modules), where the information is lost after the power is switched off. Many other types of memory are RAM as well, including most types of ROM and a type of flash memory called NOR-Flash.

An early type of widespread writable random-access memory was the magnetic core memory, developed from 1949 to 1952, and subsequently used in most computers up until the development of the static and dynamic integrated RAM circuits in the late 1960s and early 1970s. Before this, computers used relays, delay line/delay memory, or various kinds of vacuum tube arrangements to implement "main" memory functions (i.e., hundreds or thousands of bits), some of which wererandom access, some not. Latches built out of vacuum tube triodes, and later, out of discrete transistors, were used for smaller and faster memories such as random-access register banks and registers. Prior to the development of integrated ROM circuits, permanent (or read-only) random-access memory was often constructed using semiconductor diode matrices driven by address decoders.

Modern types of writable RAM generally store a bit of data in either the state of a flip-flop, as in SRAM (static RAM), or as a charge in a capacitor (or transistor gate), as in DRAM (dynamic RAM), EPROMEEPROM and Flash. Some types have circuitry to detect and/or correct random faults called memory errors in the stored data, using parity bits or error correction codes. RAM of the read-only type, ROM, instead uses a metal mask to permanently enable/disable selected transistors, instead of storing a charge in them. Of special consideration is SIMM and DIMM memory modules.
SRAM and DRAM are volatile, other forms of computer storage, such as disks and magnetic tapes, have been used aspersistent storage in traditional computers. Many newer products instead rely on flash memory to maintain data when not in use, such as PDAs or small music players. Certain personal computers, such as many rugged computers andnetbooks, have also replaced magnetic disks with flash drives. With flash memory, only the NOR type is capable of true random access, allowing direct code execution, and is therefore often used instead of ROM; the lower cost NAND type is commonly used for bulk storage in memory cards and solid-state drives.

A memory chip is an integrated circuit (IC) made of millions of transistors and capacitors. In the most common form of computer memory, dynamic random access memory (DRAM), a transistor and a capacitor are paired to create a memory cell, which represents a single bit of data. The capacitor holds the bit of information — a 0 or a 1 . The transistor acts as a switch that lets the control circuitry on the memory chip read the capacitor or change its state.

eXaMs.. zzZZz..




a perfect student is not the one who read books before exam,
but
writes a new book in the exam! with innovative ideas n outstanding theories.
:----------------------------

arz kiya hai- 
wo mud ke hame dekh rahe the or hum unhe


wo mud k hame dekh rahe the or hum unhe

kyoki xam me na unhe ku6 ata tha na hame.
:----------------------------

once rajnikant appeard for b.e.(b.tech.) xam n guess wat..

..
he failed!!
.b.e. hai mazak hai kya..bade bado ki fat jati hai...
:----------------------------

its such a funny situation. we hv no idea wt 2 write in d xam paper n d supervisor cums up n says''plz cover ur answer sheet'';-):-)
:----------------------------

xam me copy kar k pas hue jaise-taise

xam me copy kar k pas hue jaise-taise 

acp-daya pata lagao akhir munni badnam hui to hui kaise?
:----------------------------

in xam hall a gal 2 santa
"muze sirf is ans ki starting bata na..baki sab me likh lungi''
.
.
santa ne dhirese bataya..












"the"
:----------------------------

kash koi xam result ka insurance kara deta
toh har xam k pehele premium bharva dete

pass hote to thik hai

warna insurance claim karva lete
:----------------------------

saccha dost vo hota h jo
xam me apke pas wali window k samne aake bole
abey kitna likhega jaldi chal teri wali ja rhi hai..!!
:----------------------------

words by bill gates: see the clock only whn u hav no work.dont see the clock whn u r working. clock is a lock 4 succes.
best luck 4 xam guys
:----------------------------

2 trees katne pr
15 papr bante h
wich v use in 1 xam.
join us 2 save trees 
say no to xams fwrd it 2 al gud studnts
xam hatao!
trees bachao!

:----------------------------
height of honesty:
,
_

sitting in an exam hall,
_
opening a chit,
_
  memorizing it,
_
then writing without
looking to it !
:----------------------------

all students
attitude towards exams:

"today is my exam,
but
i don't care.
bcos,
a single sheet of paper cant decide my future
:----------------------------

2 thoughts decide the progress in life :
The way U manage when U have nothing in hand
&
The way U interact when U have everything in hand.
:----------------------------

in examination hall
how do boys manage the time?

1)counting how many windows
& doors.
2)seeing the brand name of the pen..

boyz rokz.
:----------------------------

Engineering facts: A thin film of air only 0.025mm thick may resist as much heat transfer as a wall of copper 400mm thick!!
:----------------------------

hundred words don''''t give pain
.
but,
a true frnd''''s silence
hurts a lot
.
.
.
.
.
.
.
especially in d examination hall!
:----------------------------


brain is d most outstanding objct in d nature..
it functions 24hrs,365days frm d time v r born &

stop only wen


v entr d examination hall
:----------------------------

friendship quotes