The map save file

The companion CIVIL?.MAP saves graphics page 2, which holds the map database. read_save() calls image_screen(2, file); load_save() restores it through load_screen(). Despite its name, read_save() is the writing routine.

The decoded page has 320 columns and 200 rows. At that level, byte position y * 320 + x corresponds to a page coordinate. The MAP file itself uses the screen-image encoder, including framing and compression. It is not a fixed 64,000-byte raw dump, and page offsets are not file offsets.

Terrain codes, region numbers, site data, occupancy and improvement nibbles occupy separate areas of the decoded page. The per-civilization exploration array is stored in the SVE file, separately from the remembered improvement flags on this page.