Memory refresh is the process of periodically reading information from an area of computer memory

Computer memory

In computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which are fast In computing, memory refers to the...

, and immediately rewriting the read information to the same area with no modifications. Each memory refresh cycle refreshes a succeeding area of memory. Memory refresh is most often associated with modern dynamic random access memory

Dynamic random access memory

Dynamic random-access memory is a type of random-access memory that stores each bit of data in a separate capacitor within an integrated circuit. The capacitor can be either charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1...

. Due to the problem of fading of charge in DRAM

Dram

Dram or DRAM may refer to:As a unit of measure:* Dram , an imperial unit of mass and volume* Armenian dram, a monetary unit* Dirham, a unit of currency in several Arab nationsOther uses:...

 information stored in capacitors become 1's to 0's.To prevent this from happening,design engineers adds an extra circuitry to recharge cells periodically. This process is refresh. If a cell

Cell

-Science and technology:*Cell , the functional basic unit of life*Cell , a term used in an electronic circuit design schematics*Cell , a three-dimensional element, part of a higher-dimensional object*Cell , a scientific journal...

 is less than half recharged,it is determined to be zero,and cell is not recharged.

However, several early computer memory technologies also required periodical processes similar in purpose. These technologies include delay line memory

Delay line memory

Delay line memory was a form of computer memory used on some of the earliest digital computers. Like many modern forms of electronic computer memory, delay line memory was a refreshable memory, but as opposed to modern random-access memory, delay line memory was serial-access...

 and Williams tube

Williams tube

The Williams tube or the Williams-Kilburn tube , developed in about 1946 or 1947, was a cathode ray tube used to electronically store binary data....

.

Compare with magnetic core memory

Magnetic core memory

Magnetic-core memory was the predominant form of random-access computer memory for 20 years . It uses tiny magnetic toroids , the cores, through which wires are threaded to write and read information. Each core represents one bit of information...

 where each memory cell needs to be refreshed after being read, but periodical refreshes are not necessary. Also, see static random access memory

Static random access memory

Static random-access memory is a type of semiconductor memory where the word static indicates that, unlike dynamic RAM , it does not need to be periodically refreshed, as SRAM uses bistable latching circuitry to store each bit...

which is used in similar applications as dynamic random access memory, but does not require refreshing (hence labelled static as opposed to dynamic).