Field Guide · hardware

Also known as: RAM, random-access memory, memory

Random-access memory (RAM) is a computer’s fast, temporary working storage — it holds the data and programs in active use so the CPU can reach them quickly.1

One DRAM cell: 1 transistor + 1 capacitor bit line T word line (select) capacitor holds charge = the bit Cells in a grid — addressed by row × column one row charge leaks → rows refreshed constantly · all lost at power-off (volatile)
Each DRAM cell is just one transistor guarding one tiny capacitor, and the stored bit is the charge on that capacitor. Cells pack into a row-and-column grid, read by selecting a word line onto a bit line. Because the charge leaks, every row must be refreshed thousands of times a second — and it all disappears the instant power is removed, which is what makes RAM volatile.

Overview

RAM is volatile: its contents are lost the moment power is removed. That is the key contrast with storage, which is permanent. When you open a program, the device copies what it needs from storage into RAM, works there at high speed, then saves anything worth keeping back to storage before shutting down.

More RAM lets a device hold more programs and larger data sets in active use at once. Run out, and the system slows to a crawl as it shuffles data back and forth with slower storage.

Where it fits

RAM is one of the four building blocks of computer hardware, and its size tracks the hardware spectrum: a microcontroller may have only a few kilobytes, a phone several gigabytes, and a large server terabytes.

Sources

  1. Random-access memory — Wikipedia, on RAM as fast volatile working memory. ↩

See also

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