Semicolony ELI5 · comic

Virtual memory.

Giving every program its own private, tidy address space, while the OS quietly maps it onto the real, messy RAM.

Apartment 1, all mine.

1
Every program gets its own tidy address space, starting at zero, as if it owned the machine.
Send it to flat 42.

2
When it reads an address, that’s a make-believe one — a flat number, not a real location.
3
The page table is the post office: it looks up where that page really sits in RAM.
No address for next door.

4
Each program has its own mapping, so one literally can’t name another’s memory.
One moment, retrieving…

5
If the page was parked on disk, a page fault fetches it back before work continues.
Why is everything frozen?

6
Too much of that and pages ping-pong to slow disk — thrashing grinds it to a crawl.

Each program uses simple apartment numbers; the OS post office knows the real address behind every one.

Semicolony semicolony.dev/eli5/virtual-memory/comic