Kind of useful if someone were going to try and disassemble the thing or create an emulator or simulator that would allow you to see instructions being made and some of this allow user input in cmd/resp format so you can see what is happening at machine level or even pause things or slow them down etc I've seen this before but this is normally more of an assembly based thing while not related to basic directly it is related indirectly so might be useful for those on the search.
0x00000000 **** Exc Protected area
0x20000000 **** --- Unmapped, repeated pattern
0x3FF00000 0x010000 R/W Memory-mapped I/O, repeated every 0x100.
0x3FF10000 0x010000 R only Mapped, zeroes
0x3FF20000 0x001800 R/W I/O registers
0x3FF21800 0x09E800 R only Mapped, zeroes
0x3FFC0000 0x020000 --- Unmapped, repeated pattern
0x3FFE0000 0x008000 R only Mapped, zeroes
0x3FFE8000 0x014000 R/W User data RAM. Available to applications.
0x3FFFC000 0x004000 R/W ETS system data RAM.
0x40000000 0x010000 R only Internal ROM.
0x40010000 0x010000 R only Internal ROM (repeated 0x40000000).
0x40020000 0x0E0000 R only Mapped, zeroes
0x40100000 0x008000 R/W RAM
0x40108000 0x038000 R only Mapped, zeroes
0x40140000 0x0C0000 --- Unmapped, repeated pattern
0x40200000 0x100000 R only SPI Flash is mapped (512k->2x repeated, 16Mb - 1Mb mapped )
0x40300000 **** --- Unmapped, repeated pattern
0x60000000 0x001000 R/W I/O registers
0x60001000 0x000400 R/W RAM
0x60001400 0x000400 R/W I/O registers
0x60001800 0x000400 R/W RAM (repead 0x60001000)
0x60001C00 0x000400 R/W I/O registers (repeated 0x60001400)
Where I buy my ESP8266 boards from... (Banggood)