Editing Atari 1200XL (section)

== Memory and Storage ==
The 1200XL contains:
* '''64 KB RAM''' – organised as eight 64K×1 DRAM chips (4164-type), one per data line (U1–U9, with U7 as address decoding). 48 KB is directly available to programs, with the remaining 16 KB shared with ROM and I/O address space, accessible via bank switching controlled by the MMU.
* '''16 KB ROM''' – two 8K×8 ROM chips (U12, U13) containing the operating system. Atari OS Rev. 10 shipped initially; some later units received Rev. 11 with partial compatibility fixes.

BASIC is '''not''' included in ROM. Users must load BASIC from a cartridge, cassette, or disk.

Storage options:
* '''Atari 1010 Program Recorder''' – cassette tape drive, connected via SIO.
* '''Atari 1050 Floppy Disk Drive''' – external 5.25" floppy drive, connected via SIO.
* '''Cartridge slot''' – single left-side slot (30-pin edge connector) for ROM cartridges up to 16 KB.