The Spectrum’s memory map looks chaotic until you learn its one strange rule: the screen is not stored line by line. Once that clicks, the rest of the 48K falls into place.

The landmarks

• 16384: the start of the bitmap, stored in thirds.
• 22528: the colour attributes, one byte per 8×8 cell.
• 23552: the system variables, where BASIC keeps its bookkeeping.

Once you understand why the screen loads in stripes, you understand the whole machine.

Rufus Tanaka

Poke around with PEEK and you will find the system variables, the printer buffer and eventually your own program, sitting just above them.