Redirected from Random-access memory
Computers use RAM to hold the program code and data during execution. In the first electronic computers, RAM was built from vacuum tubes, and later magnetic cores. The term "core" is still used by programmers to describe the RAM at the heart of a computer.
Many types of RAM are volatile, which means that unlike some other forms of computer storage such as disk storage and tape storage, they lose their data when the computer is powered down.
Throughout the history of computing, a variety of technologies have been used for RAM, and usually more than one in the same computer, with high-memories constructed out of the same technology as the logic, and slower, cheaper technologies used for bulk storage. Some early computers used mercury delay lines, in which a series of acoustic pulses were sent along a tube filled with mercury. When the pulse reached the end of the tube, the circuitry detected whether the pulse represented a binary 1 or 0 and caused the oscillator at the beginning of the line to repeat the pulse. Other early computers stored RAM on high-speed "magnetic drums".
Later designs used arrays of small ferrite electromagnets, known as core memory.
Modern RAM generally stores a bit of data as either a charge in a capacitor, as in dynamic RAM, or the state of a flip-flop, as in static RAM.
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