Editing Semiconductor memory (section)

==Description==
{{See also|Computer memory}}

In a semiconductor memory chip, each [[binary digit|bit]] of binary data is stored in a tiny circuit called a ''[[Memory cell (computing)|memory cell]]'' consisting of one to several [[transistor]]s.  The memory cells are laid out in rectangular arrays on the surface of the chip.  The 1-bit memory cells are grouped in small units called ''words'' which are accessed together as a single memory address. Memory is manufactured in [[word length]] that is usually a power of two, typically ''N''=1, 2, 4 or 8 bits.

Data is accessed by means of a binary number called a [[memory address]] applied to the chip's address pins, which specifies which word in the chip is to be accessed.  If the memory address consists of ''M'' bits, the number of addresses on the chip is 2<sup>''M''</sup>, each containing an ''N'' bit word.   Consequently, the amount of data stored in each chip is ''N''2<sup>''M''</sup> bits.<ref name="Dawoud" />  The memory storage capacity for ''M'' number of [[address line]]s is given by 2<sup>''M''</sup>, which is usually in power of two: 2, 4, 8, 16, 32, 64, 128, 256 and 512  and measured in [[kilobit]]s, [[megabit]]s, [[gigabit]]s or [[terabit]]s, etc. {{as of | 2014 }} the largest semiconductor memory chips hold a few gigabits of data, but higher capacity memory is constantly being developed.    By combining several integrated circuits, memory can be arranged into a larger word length and/or address space than what is offered by each chip, often but not necessarily a [[power of two]].<ref name="Dawoud" />

The two basic operations performed by a memory chip are "''read''", in which the data contents of a memory word is read out (nondestructively), and "''write''" in which data is stored in a memory word, replacing any data that was previously stored there.  To increase data rate, in some of the latest types of memory chips such as [[DDR SDRAM]] multiple words are accessed with each read or write operation.

In addition to standalone memory chips, blocks of semiconductor memory are integral parts of many computer and data processing integrated circuits.  For example, the [[microprocessor]] chips that run computers contain [[cache memory]] to store instructions awaiting execution.