6502 BBC BASIC for Acorn Atom

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BBC BASIC appears to have been initially developed on the System 5 as "Acorn New BASIC" which can be assembled at a different location to run on the Atom. The code runs at &4000-&7FFF as this is the only contiguous 16K area of RAM, workspace is at &2800, PAGE=&2C00, HIMEM=&4000. Access to the MOS is via the System/Atom MOS entry block. Only the Atom MOS, COS and DOS functions are present, all the BBC's OSWORD functions and VDU graphics functions are absent. All messages are forced to upper case. Using the System/Atom MOS API allows access AtomDOS disks, which the BBC BASIC conversion kit does not. The Atom target can also be assembled split into 4K/12K portions so it can be programmed into ROM at &A000 and &C000.
ATBASIC1 Basic1.zip	Code Source	16K 39K	BBC BASIC 1 for the Atom ("Acorn New BASIC") Source assembleable with ARM BASIC 65 to target either the Atom/System or the BBC.
ATBASIC2 Basic2.zip	Code Source	16K 54K	BBC BASIC 2.00 for the Atom Source assembleable with ARM BASIC 65 to target either the Atom/System, the BBC, or the Commodore 64.
ATBASIC2S Basic2.zip	Code Source	16K 54K	ROMmable BBC BASIC 2.00 for the Atom. First 4K stored at &A000, the next 12K at &C000. Source assembleable with ARM BASIC 65 to target either the Atom/System, the BBC, or the Commodore 64.
ATBASIC3 Basic2.zip	Code Source	16K 54K	BBC BASIC 3.10 for the Atom Source assembleable with ARM BASIC 65 to target either the Atom/System, the BBC, or the Commodore 64.
ABASIC.ssd	Disk image	50K	Atom DOS disk image with BBC BASIC 1.10, 2.00, 2.00/ROM and 3.10 Also has a few simple tools: MINI65 tiny 6502 disassembler. Press SPACE to toggle memory dump, RETURN to scroll, A to select a new address.
BBC BASIC I, II and III can be used on the Acorn Atom using the Atom BBC BASIC conversion kit. This remaps the memory and provides a small MOS interface. The minimal MOS interface only provides access to tapes, but provides some of the BBC's OSWORD and VDU functions. It was recently discovered that early versions of the BBC BASIC conversion kit came with an updated version of BASIC 1, the same version as supplied on disk for the System.
Atom			Minimal BBC OS ROM for Atom
Basic2			BBC BASIC 2
MemMap.htm			Atom memory map when using BBC BASIC
Atom			Atom documents

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Authored by J.G.Harston - Last update: 05-Apr-2018