commit f42539a517dffc81ef9a38a63cc9087d28b585d5
Author: Joshua Bell <inexorabletash@gmail.com>
Date:   Mon Dec 31 12:21:38 2018 -0800

    Snapshot: BEEPSLOT from ProDOS TRM

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..702f462
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,29 @@
+
+CC65 = ~/dev/cc65/bin
+CAFLAGS = --target apple2enh --list-bytes 0
+CCFLAGS = --config apple2-asm.cfg
+
+OUTDIR = out
+
+TARGETS = $(OUTDIR)/chtype.BIN
+
+.PHONY: clean all
+all: $(OUTDIR) $(TARGETS)
+
+$(OUTDIR):
+	mkdir -p $(OUTDIR)
+
+HEADERS = $(wildcard *.inc)
+
+clean:
+	rm -f $(OUTDIR)/*.o
+	rm -f $(OUTDIR)/*.list
+	rm -f $(OUTDIR)/$(TARGETS)
+
+
+$(OUTDIR)/%.o: %.s $(HEADERS)
+	$(CC65)/ca65 $(CAFLAGS) $(DEFINES) --listing $(basename $@).list -o $@ $<
+
+$(OUTDIR)/%.BIN $(OUTDIR)/%.SYS: $(OUTDIR)/%.o
+	$(CC65)/ld65 $(CCFLAGS) -o $@ $<
+	xattr -wx prodos.AuxType '00 20' $@
diff --git a/chtype.s b/chtype.s
new file mode 100644
index 0000000..694a4d0
--- /dev/null
+++ b/chtype.s
@@ -0,0 +1,73 @@
+
+;;;
+        .org $2000
+
+INBUF   := $200                 ;GETLN input buffer.
+WAIT    := $FCA8                ;Monitor wait routine.
+BELL    := $FF3A                ;Monitor bell routine
+EXTRNCMD        := $BE06        ;External cmd JMP vector.
+XTRNADDR        := $BE50        ;Ext cmd implementation addr.
+XLEN    := $BE52                ;Length of command string-1.
+XCNUM   := $BE53                ;CI cmd no. (ext cmd = 0).
+PBITS   := $BE54                ;Command parameter bits.
+VSLOT   := $BE61                ;Verified slot parameter.
+
+;;;
+;;; REMEMBER TO SAVE THE PREVIOUS COMMAND ADDRESS.
+;;;
+        LDA EXTRNCMD+1
+        STA NXTCMD
+        LDA EXTRNCMD+2
+        STA NXTCMD+1
+;;;
+        LDA #>BEEPSLOT          ;Install the address of our
+        STA EXTRNCMD+1          ; command handler in the
+        LDA #<BEEPSLOT          ; external command JMP
+        STA EXTRNCMD+2          ; vector.
+        RTS
+;;;
+BEEPSLOT:       LDX #0          ;Check for our command.
+NXTCHR: LDA INBUF,X             ;Get first character.
+        CMP CMD,X               ;Does it match?
+        BNE NOTOURS             ;NO, SO CONTINUE WITH NEXT CMD.
+        INX                     ;Next character
+        CPX #CMDLEN             ;All characters yet?
+        BNE NXTCHR              ;No, read next one.
+;;;
+        LDA #CMDLEN-1           ;Our cmd! Put cmd length-1
+        STA XLEN                ; in CI global XLEN.
+        LDA #>EXECUTE           ;Point XTRNADDR to our
+        STA XTRNADDR            ; command execution
+        LDA #<EXECUTE           ; routine
+        STA XTRNADDR+1
+        LDA #0                  ;Mark the cmd number as
+        STA XCNUM               ; zero (external).
+;;;
+        LDA #%00010000          ;Set at least one bit
+        STA PBITS               ; in PBITS low byte!
+;;;
+        LDA #%00000100          ;And mark PBITS high byte
+        STA PBITS+1             ; that slot & drive are legal.
+        CLC                     ;Everything is OK.
+        RTS                     ;Return to BASIC.SYSTEM
+;;;
+EXECUTE:        LDA VSLOT       ;Get slot parameter.
+        TAX                     ;Transfer to index reg.
+NXTBEEP:        JSR BELL        ;Else, beep once.
+        LDA #$80                ;Set up the delay
+        JSR WAIT                ; and wait.
+        DEX                     ;decrement index and
+        BNE NXTBEEP             ; repeat until x = 0.
+        CLC                     ;All done successfully.
+        RTS                     ;Back to BASIC.SYSTEM.
+;;;
+;;; IT'S NOT OUR COMMAND SO MAKE SURE YOU LET BASIC
+;;; CHECK WHETER OR NOT IT'S THE NEXT COMMAND.
+;;;
+NOTOURS:        SEC             ;SET CARRY AND LET
+        JMP (NXTCMD)            ; NEXT EXT CMD GO FOR IT.
+;;;
+CMD:    .byte   "BEEPSLOT"      ;Our command
+        CMDLEN =  *-CMD         ;Our command length
+NXTCMD: .word   0               ; STORE THE NEXT COMMAND'S
+                                ; ADDRESS HERE.