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• In the early 1940s, memory was only available up to a few bytes of space. One of the more significant signs of progress during this time was the invention of acoustic delay line memory
• Acoustic delay line memory . This technology enabled delay lines to store bits as sound waves in mercury, and quartz crystals to act as transducers to read and write bits
• In the late 1940s, nonvolatile memory began to be researched, and magnetic-core memory
• magnetic-core memory

  • which enabled the recall of memory after a loss of power was created
• By the 1950s, this technology had been improved and commercialized and led to the invention of PROM in 1956.
• Magnetic-core memory

  became so widespread that it was the main form of memory until the 1960s.
• Metal-oxide-semiconductor field-effect transistors, also known as MOS semiconductor memory, was invented in 1959.
• MOS semiconductor memory

  This enabled the use of MOS transistors as elements for memory cell storage.
• MOS memory

  was cheaper and needed less power compared to magnetic-core memory.
• Bipolar memory

  , which used bipolar transistors, started being used in the early 1960s.​​
• In 1961, Bob Norman proposed the concept of solid-state memory being used on an integrated circuit (IC) chip
• IBM brought memory into the mainstream in 1965
• Other advancements during the early to mid-1960s were the invention of bipolar SRAM,
• Toshiba's introduction of DRAM in 1965 and the commercial use of SRAM in 1965. ​
• The single-transistor DRAM cell was developed in 1966
• MOS semiconductor device used to create ROM in 1967.
• From 1968 to the early 1970s, N-type MOS (NMOS) memory also started to become popularized.
• By the early 1970s, MOS-based memory started becoming much more widely used as a form of memory
• In 1970, Intel had the first commercial DRAM IC chip.
• erasable PROM was developed and EEPROM was invented in 1972.