MOS memory was developed by John Schmidt at Fairchild Semiconductor in 1964. The invention of the metal–oxide–semiconductor field-effect transistor ( MOSFET) enabled the practical use of metal–oxide–semiconductor (MOS) transistors as memory cell storage elements. While semiconductor memory offered improved performance over magnetic-core memory, it remain larger and more expensive and did not displace magnetic-core memory until the late 1960s. The first bipolar semiconductor memory IC chip was the SP95 introduced by IBM in 1965. The same year, the concept of solid-state memory on an integrated circuit (IC) chip was proposed by applications engineer Bob Norman at Fairchild Semiconductor. Semiconductor memory made from discrete devices was first shipped by Texas Instruments to the United States Air Force in 1961. The first semiconductor memory was implemented as a flip-flop circuit in the early 1960s using bipolar transistors. Magnetic-core memory was the dominant form of memory until the development of MOS semiconductor memory in the 1960s. Rajchman in the early 1950s, before being commercialized with the Whirlwind computer in 1953. Viehe and An Wang in the late 1940s, and improved by Jay Forrester and Jan A. Magnetic-core memory allowed for recall of memory after power loss. The Williams tube was nevertheless frustratingly sensitive to environmental disturbances.Įfforts began in the late 1940s to find non-volatile memory. The Williams tube was able to store more information than the Selectron tube (the Selectron was limited to 256 bits, while the Williams tube could store thousands) and less expensive. Using cathode-ray tubes, Fred Williams invented the Williams tube, which was the first random-access computer memory. Two alternatives to the delay line, the Williams tube and Selectron tube, originated in 1946, both using electron beams in glass tubes as means of storage. Delay-line memory was limited to a capacity of up to a few thousand bits. Through the construction of a glass tube filled with mercury and plugged at each end with a quartz crystal, delay lines could store bits of information in the form of sound waves propagating through the mercury, with the quartz crystals acting as transducers to read and write bits. The next significant advance in computer memory came with acoustic delay-line memory, developed by J.

The first electronic programmable digital computer, the ENIAC, using thousands of vacuum tubes, could perform simple calculations involving 20 numbers of ten decimal digits stored in the vacuum tubes. In the early 1940s, memory technology often permitted a capacity of a few bytes.

1951 8 GB microSDHC card on top of 8 bytes of magnetic-core memory (1 core is 1 bit.) History Electromechanical memory used in the IBM 602, and early punch multiplying calculator Detail of the back of a section of ENIAC, showing vacuum tubes Williams tube used as memory in the IAS computer c. Each word can be accessed by a binary address of N bits, making it possible to store 2 N words in the memory. The memory cells are grouped into words of fixed word length, for example, 1, 2, 4, 8, 16, 32, 64 or 128 bits. Flash memory organization includes both one bit per memory cell and multi-level cell capable of storing multiple bits per cell. Most semiconductor memory is organized into memory cells each storing one bit (0 or 1). Examples of volatile memory are dynamic random-access memory (DRAM) used for primary storage, and static random-access memory (SRAM) used for CPU cache. Examples of non-volatile memory are flash memory and ROM, PROM, EPROM and EEPROM memory.

There are two main kinds of semiconductor memory: volatile and non-volatile. Modern computer memory is implemented as semiconductor memory, where data is stored within memory cells built from MOS transistors and other components on an integrated circuit. If needed, contents of the computer memory can be transferred to storage a common way of doing this is through a memory management technique called virtual memory. Operating systems borrow RAM capacity for caching so long as not needed by running software.

Besides storing opened programs, computer memory serves as disk cache and write buffer to improve both reading and writing performance. Ĭomputer memory operates at a high speed compared to storage which is slower but less expensive and higher in capacity. The term memory is often synonymous with the term primary storage or main memory. Ĭomputer memory stores information, such as data and programs for immediate use in the computer. As of 2021, over 90 percent of computer memory used in PCs and servers was of this type.

Computer memory chart images