Electronics

Memory (RAM)

When someone says "this machine has 16 GB of RAM," this is what they mean — the fast, working memory a CPU actively reads and writes while a program runs. It's a completely different thing from storage, in one way that matters more than any speed or capacity number: what happens when the power goes off.

Volatile — the defining property

RAM's single defining trait is that it's volatile: every bit it holds vanishes the instant power is removed. That's the direct, deliberate contrast with ROM and storage — this page is fast because it doesn't have to guarantee anything survives past the next power cycle, a guarantee non-volatile memory has to work much harder (and slower) to provide.

DRAM vs. SRAM

DRAM

What "RAM" almost always means in practice — a capacitor per bit that leaks charge and must be constantly refreshed thousands of times a second. Cheap and dense, which is why it's used for a system's main memory, measured in GB.

SRAM

Built from transistor latches instead of capacitors — no refresh needed, meaningfully faster, but far more expensive and less dense per chip area. Used for CPU cache and for a microcontroller's own small internal RAM, where every extra nanosecond of latency and every microwatt of power actually matters.

Why more RAM helps

When active data no longer fits in RAM, the operating system starts swapping — temporarily writing some of it out to much slower storage to make room, then reading it back when needed again. This is the actual mechanism behind "why is my computer crawling with 50 browser tabs open" — not the CPU struggling, but RAM running out and the system falling back to a component hundreds of times slower to compensate.

Where memory sits in the hierarchy

CPU registers and cache are faster and smaller than RAM; storage is far larger and far slower. RAM is the middle tier — big enough to hold an entire running program's active data, fast enough that the CPU isn't constantly stalled waiting on it, but not fast enough to skip cache, and not persistent enough to skip storage.

Real-world applications

• Every general-purpose computer — desktops, laptops, servers, phones — measured directly in the GB spec sheets advertise.
• Database and cache servers — systems specifically built to hold enormous datasets in RAM for the speed of never having to touch disk during normal operation.
• Embedded microcontrollers — a tiny amount of on-chip SRAM (often just KB, not GB) holds a running firmware's variables and stack — see the Embedded C domain for how that space actually gets divided up in a running program.

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