Add in-memory bootstrapping system

This should help with the bootstrapping of non-emulated environment.
For example, I have a problem with the RC2014: I can't send it
bootstrap info until the ACIA is up. I need to find a way...

emul/Makefile

@@ -16,6 +16,7 @@ $(SLATEST):
 forth/forth0.bin: $(SLATEST)
 	cat forth/boot.bin forth/z80c.bin > $@
 	$(SLATEST) $@
+	cat forth/emul.fs >> $@
 
 forth/forth0-bin.h: forth/forth0.bin
 	./bin2c.sh KERNEL < forth/forth0.bin | tee $@ > /dev/null
@@ -56,7 +57,7 @@ emul.o: emul.c
 .PHONY: updatebootstrap
 updatebootstrap: forth/stage2
 	cat ./forth/conf.fs ../forth/boot.fs | ./forth/stage2 | tee forth/boot.bin > /dev/null
-	cat ./forth/conf.fs ../forth/z80c.fs forth/emul.fs ../forth/icore.fs | ./forth/stage2 | tee forth/z80c.bin > /dev/null
+	cat ./forth/conf.fs ../forth/z80c.fs ../forth/icore.fs | ./forth/stage2 | tee forth/z80c.bin > /dev/null
 
 .PHONY: clean
 clean:

emul/forth/emul.fs

@@ -1,17 +1,3 @@
-( Implementation fo KEY and EMIT in the emulator
-  stdio port is 0
-)
-
-CODE EMIT
-    HL POPqq,
-    chkPS,
-    A L LDrr,
-    0 OUTnA,
-;CODE
-
-CODE KEY
-    0 INAn,
-    H 0 LDrn,
-    L A LDrr,
-    HL PUSHqq,
-;CODE
+: EMIT 0 PC! ;
+: KEY 0 PC@ ;
+: (c<) KEY ;

forth/icore.fs

@@ -189,13 +189,22 @@
     AGAIN
 ;
 
+( system c< simply reads source from binary, starting at
+  LATEST. Convenient way to bootstrap a new system. )
+: (c<)
+    ( 51 == SYSTEM SCRATCHPAD )
+    0x51 _c RAM+ _c @   ( a )
+    _c DUP _c C@        ( a c )
+    _c SWAP 1 _c +      ( c a+1 )
+    0x51 _c RAM+ _c !   ( c )
+;
+
 : BOOT
     LIT< (parse) _c (find) _c DROP _c (parse*) _c !
-    LIT< (c<) _c (find) _c
-    NOT IF LIT< KEY _c (find) _c DROP THEN
+    ( 51 == SYSTEM SCRATCHPAD )
+    _c CURRENT _c @ 0x51 _c RAM+ _c !
     ( 0c == CINPTR )
-    0x0c _c RAM+ _c !
-    LIT< (c<$) _c (find) IF EXECUTE ELSE _c DROP THEN
+    LIT< (c<) _c (find) _c DROP 0x0c _c RAM+ _c !
     LIT< INIT _c (find)
     IF EXECUTE
     ELSE _c DROP _c INTERPRET THEN

forth/notes.txt

@@ -88,7 +88,8 @@ RAMSTART   INITIAL_SP
 +0e        WORDBUF
 +2e        SYSVNXT
 +4e        INTJUMP
-+51        RAMEND
++51        SYSTEM SCRATCHPAD
++60        RAMEND
 
 INITIAL_SP holds the initial Stack Pointer value so that we know where to reset
 it on ABORT
@@ -113,3 +114,30 @@ INTJUMP All RST offsets (well, not *all* at this moment, I still have to free
 those slots...) in boot binaries are made to jump to this address. If you use
 one of those slots for an interrupt, write a jump to the appropriate offset in
 that RAM location.
+
+SYSTEM SCRATCHPAD is reserved for temporary system storage.
+
+*** Initialization sequence
+
+On boot, we jump to the "main" routine in boot.fs which does very few things.
+It sets up the SP register, CURRENT and HERE to LATEST (saved in stable ABI),
+then look for the BOOT word and calls it.
+
+In a normal system, BOOT is in icore and does a few things:
+
+1. Find "(parse)" and set "(parse*)" to it.
+2. Find "(c<)" a set CINPTR to it (what C< calls).
+3. Write LATEST in SYSTEM SCRATCHPAD ( see below )
+4. Find "INIT". If found, execute. Otherwise, execute "INTERPRET"
+
+On a bare system (only boot+icore), this sequence will result in "(parse)"
+reading only decimals and (c<) reading characters from memory starting from
+CURRENT (this is why we put CURRENT in SYSTEM SCRATCHPAD, it tracks current
+pos ).
+
+This means that you can put initialization code in source form right into your
+binary, right after your last compiled dict entry and it's going to be executed
+as such until you set a new (c<).
+
+Note that there is no EMIT in a bare system. You have to take care of supplying
+one before your load core.fs and its higher levels.