Implement backslash line continuation character

README.md

@@ -52,8 +52,9 @@ Unless otherwise specified, the assembler generally follows the source conventio
 
 ### Extensions
 
-- `.` may be used as PC in expressions
+- `.` may be used as PC
 - `;` may be used instead of `*` to introduce comments
+- `\` may be used to continue a line
 
 ### Unimplemented directives
 
@@ -71,7 +72,6 @@ Unless otherwise specified, the assembler generally follows the source conventio
 - `%` binary prefix
 - `$` in symbol name
 - `.` in middle of symbol name
-- `\` line continuation character
 - signed arithmetic, greater than 16 bits
 - forward references in FCB directives.
 
@@ -84,6 +84,8 @@ Unless otherwise specified, the assembler generally follows the source conventio
 	- Use of forward reference in EQU or ORG directives.
 	- Source or program buffer overflow.
 - Support for signed division removed; tests have NOT been updated.
+- `\` is treated as a continuation character only outside of quotes
+- `\` at end of a quoted string is treated as a literal character
 
 ## Memory Layout
 

asm68.s

@@ -264,6 +264,7 @@ isend
 *--------------------------------------------------------------------
 nsrc
 	clr	qotflg	* clear quote flag
+	clr	cntflg	* clear continuation flag
 * initialize current line = 0
 	ldx	#-1	* init line number to -1
 	stx	line
@@ -291,15 +292,34 @@ nsrc
 	bsr	isend	* check for ESC or EOT (end of input)
 	beq	.nsrc	* return
 	bsr	iscom	* check for comment character
-	bne	.ntcom	* if not comment, continue below
+	bne	.cntchk	* if not comment, check continuation
 	bsr	lincom	* set up for line comment
+	bra	.ntcom
+*--------------------------------------------------------------------
+.cntchk	cmpa	#CONT	* check for continuation char '\'
+	bne	.ntcom	* if not continuation, continue below
+	tst	qotflg	* in quote mode?
+	bne	.ntcom	* if in quotes, treat as regular character
+	ldaa	#CR	* continuation char at end of line
+	jsr	ECHO	* echo CR only, not backslash
+	bra	.nxtch	* continue reading (skip storing '\')
+*--------------------------------------------------------------------
 .ntcom	cmpa	#CR	* end of line?
 	bne	.notcr	* skip if not end of line
+	tst	cntflg	* check continuation flag
+	bne	.cntcr	* if continuing, handle below
 	tst	column	* blank line?
 	bne	.ntblk	* skip if not blank line
 	ldaa	#EMPTY	* store blank line marker
 	staa	,x
 	inx
+*--------------------------------------------------------------------
+* cntcr - Handle carriage return with continuation active
+**********************************************************************
+.cntcr	clr	cntflg	* clear continuation flag
+	bsr	newline	* output newline
+	bra	.nxtch	* continue reading same line
+*--------------------------------------------------------------------
 .ntblk	ldaa	#NUL	* ACC A = end-of-line marker (NUL)
 	staa	,x	* store here & pass to tokmne below
 	inx
@@ -309,13 +329,18 @@ nsrc
 *--------------------------------------------------------------------
 .notcr	cmpa	#BSIN
 	bne	.notbs	* if BS, delete typed characters...
-	ldx	linptr	* restore X (start of current line)
+	tst	cntflg	* check continuation flag
+	beq	.bkspc	* if not continuing, normal backspace
+	clr	cntflg	* else, clear continuation flag
+	bra	.rdlin		* and restart line input
+*--------------------------------------------------------------------
+.bkspc	ldx	linptr	* restore X (start of current line)
 	inc	column	* column++
-.bkspc	dec	column	* column--
+.bspcl	dec	column	* column--
 	beq	.rdlin	* already at start of line?
 	ldaa	#BS	* no, emit backspace character
 	jsr	ECHO
-	bra	.bkspc	* and loop
+	bra	.bspcl	* and loop
 *--------------------------------------------------------------------
 .notbs
 	bsr	fldsp	* check for field separator

defs.s

@@ -18,6 +18,7 @@ BSIN	equ	$5F	* Apple-1 uses _ key as rubout
 HT	equ	$09	* ASCII horizontal tab
 CR	equ	$0D	* ASCII carriage return
 ESC	equ	$1B	* ASCII escape
+CONT	equ	$5C	* ASCII backslash (line continuation)
 
 _	equ	$7F	* we use $7F (DEL) as underscore
 
@@ -83,7 +84,7 @@ opcptr	equ	$001E	* (2 bytes) current opcode entry during search
 jmpbuf	equ	$0020	* (4 bytes) stack pointer (S) to restore
 * $24-$38 reserved by wozmon
 symoff	equ	$0039	* (1 byte) symbol definition offset
-* $3A-$3B available
+cntflg	equ	$003A	* (1 byte) line continuation flag
 fwdrok	equ	$003C	* (1 byte) forward ref allowed?
 column	equ	$003D	* (1 byte) column index (n/l commands)
 mneitr	equ	$003E	* (1 byte) mnemonic search pass count

tests/cnttst.s

@@ -0,0 +1,29 @@
+**********************************************************************
+* Line Continuation Test
+*  Tests for backslash line continuation feature
+**********************************************************************
+
+* Test 1: Simple continuation in operand field
+T1_LBL	LDAA	#$10 \
+	ADDB	#$20
+
+* Test 2: Continuation in mnemonic field
+	LDX	#$200 \
+	STAA	0,X
+
+* Test 3: Multiple continuations
+	LDAA	#$01 \
+	ADDB	#$02 \
+	STAA	$300
+
+* Test 4: Backslash in quoted string (should be literal)
+	FCC	"test\"literal"
+
+* Test 5: Continuation in comment field
+	LDAA	#$10 * comment continues \
+	ADDB	#$20
+
+* Expected behavior:
+* - Tests 1-3: Lines should continue without terminating
+* - Test 4: Backslash in quotes should be literal, not continuation
+* - Test 5: Comment should continue (not tested by assembler, but stored)