add files for BASIC interpretor main loop and message printing

c64/basic/,aliases.s

@@ -53,7 +53,8 @@
 	.alias rs232_rx_buffer_ptr $F7
 	.alias rs232_tx_buffer_ptr $F9
 
-
+	.alias basic_input_buffer $0200
+	
 	; "Compute's Mapping the 64" book
 	.alias keyboard_buffer $0277
 	.alias MEMSTR $0281

c64/basic/ab1e.print_string.s

@@ -0,0 +1,36 @@
+	;; Print string at $YYAA
+	;; Compute's Mapping the 64 p101
+
+print_string:
+	;; Setup pointer	
+	sty temp_string_ptr+1
+	sta temp_string_ptr+0
+
+	txa			
+	pha
+
+	;; Get offset ready
+	ldy #$00
+
+print_string_loop:	
+	;; Save Y in X, since X is preserved by chrout, but Y is not
+	tya
+	tax
+
+	lda (temp_string_ptr),y
+	beq print_string_end
+
+	jsr $FFD2 		; KERNAL CHROUT
+
+	txa
+	tay
+
+	iny
+	bne print_string_loop
+
+
+print_string_end:
+
+	pla
+	tax
+	rts

c64/basic/basic_do_error.s

@@ -0,0 +1,39 @@
+	;; Compute's Mapping the 64 p93
+
+basic_do_error:
+
+
+
+
+
+
+basic_error_messages:
+	.byte "TOO MANY FILES",0
+	.byte "FILE OPEN",0
+	.byte "FILE NOT OPEN",0
+	.byte "FILE NOT FOUND",0
+	.byte "DEVICE NOT PRESENT",0
+	.byte "NOT INPUT FILE",0
+	.byte "NOT OUTPUT FILE",0
+	.byte "MISSING FILENAME",0
+	.byte "ILLEGAL DEVICE NUMBER",0
+	.byte "NEXT WITHOUT FOR",0
+	.byte "SYNTAX",0
+	.byte "RETURN WITHOUT GOSUB",0
+	.byte "OUT OF DATA",0
+	.byte "ILLEGAL QUANTITY",0
+	.byte "OVERFLOW",0
+	.byte "OUT OF MEMORY",0
+	.byte "UNDEF'D STATEMENT",0
+	.byte "BAD SUBSCRIPT",0
+	.byte "REDIM'D ARRAY",0
+	.byte "DIVISION BY ZERO",0
+	.byte "ILLEGAL DIRECT",0
+	.byte "TYPE MISMATCH",0
+	.byte "STRING TOO LONG",0
+	.byte "FILE DATA",0
+	.byte "FORMULA TOO COMPLEX",0
+	.byte "CAN'T CONTINUE",0
+	.byte "UNDEF'D FUNCTION",0
+	.byte "VERIFY",0
+	.byte "LOAD",0

c64/basic/basic_main_loop.s

@@ -0,0 +1,27 @@
+basic_main_loop:
+
+	;; XXX - Check if direct or program mode, and get next line of input
+	;; the appropriate way.
+	;; XXX - For now, it is hard coded to direct mode
+	
+	;; Read a line of input
+	ldx #$00
+read_line_loop:	
+	jsr $ffe4 		; KERNAL CHRIN
+	cmp #$0d
+	beq got_line_of_input
+	;; Not carriage return, so try to append to line so far
+	cpx #80
+	bcc +
+	;; Report STRING TOO LONG error (Compute's Mapping the 64 p93)
+	ldx #23
+	jmp basic_do_error
+*
+	sta basic_input_buffer,x
+	inx
+	jmp read_line_loop
+
+got_line_of_input:	
+	jsr ready_message
+
+	jmp basic_main_loop

c64/basic/basic_warm_start.s

@@ -1,6 +1,6 @@
 	;; Clear screen etc, show READY prompt.
 
 basic_warm_start:
-	* 	inc $d020
-	jmp -
+	jsr ready_message
+	jmp basic_main_loop
 	

c64/basic/ready_message.s

@@ -0,0 +1,5 @@
+ready_message:
+	;; See src/make_error_tables.c for packed message handling
+	;; information.
+	ldx #0
+	jmp print_packed_message