diff --git a/Makefile b/Makefile
index 92dff008..7dcd2041 100644
--- a/Makefile
+++ b/Makefile
@@ -20,6 +20,7 @@ SRCDIR_BASIC   = $(SRCDIR_COMMON) \
                  src/basic/basic_functions \
                  src/basic/board_m65 \
                  src/basic/board_x16 \
+                 src/basic/editor \
                  src/basic/engine \
                  src/basic/init \
                  src/basic/math \
@@ -28,7 +29,6 @@ SRCDIR_BASIC   = $(SRCDIR_COMMON) \
                  src/basic/memory \
                  src/basic/print \
                  src/basic/rom_revision \
-                 src/basic/tokenizer \
                  src/basic/wedge
 
 SRCDIR_KERNAL  = $(SRCDIR_COMMON) \
diff --git a/src/basic/basic_commands/cmd_list.s b/src/basic/basic_commands/cmd_list.s
index be79ad4c..d1b8b75b 100644
--- a/src/basic/basic_commands/cmd_list.s
+++ b/src/basic/basic_commands/cmd_list.s
@@ -31,7 +31,7 @@ list_loop:
 	// LIST terminates any running program,
 	// because it has fiddled with the current line pointer.
 	// (Confirmed by testing on a C64)
-	jmp basic_main_loop
+	jmp shell_main_loop
 
 list_more_lines:
 	lda STKEY
diff --git a/src/basic/basic_commands/cmd_load_verify.s b/src/basic/basic_commands/cmd_load_verify.s
index aab37558..868c7406 100644
--- a/src/basic/basic_commands/cmd_load_verify.s
+++ b/src/basic/basic_commands/cmd_load_verify.s
@@ -80,4 +80,4 @@ cmd_load_no_error:
 
 cmd_load_end:
 
-	jmp basic_main_loop
+	jmp shell_main_loop
diff --git a/src/basic/basic_commands/cmd_new.s b/src/basic/basic_commands/cmd_new.s
index ce879826..d2186c3f 100644
--- a/src/basic/basic_commands/cmd_new.s
+++ b/src/basic/basic_commands/cmd_new.s
@@ -9,4 +9,4 @@ cmd_new:
 
 	// NEW command terminates execution (confirmed on a C64)
 
-	jmp basic_main_loop
+	jmp shell_main_loop
diff --git a/src/basic/basic_commands/cmd_run_goto.s b/src/basic/basic_commands/cmd_run_goto.s
index 65570149..dc93da96 100644
--- a/src/basic/basic_commands/cmd_run_goto.s
+++ b/src/basic/basic_commands/cmd_run_goto.s
@@ -18,7 +18,7 @@ cmd_goto:
 	bcs !+
 
 	jsr basic_parse_line_number
-	jsr basic_find_line
+	jsr find_line
 	bcc !+
 	// Line does not exist, so report error
 	jmp do_UNDEFD_STATEMENT_error
diff --git a/src/basic/basic_commands/cmd_stop_end.s b/src/basic/basic_commands/cmd_stop_end.s
index 51c4906e..3cf6f64c 100644
--- a/src/basic/basic_commands/cmd_stop_end.s
+++ b/src/basic/basic_commands/cmd_stop_end.s
@@ -27,4 +27,4 @@ cmd_stop:
 
 cmd_end:
 
-	jmp basic_main_loop
+	jmp shell_main_loop
diff --git a/src/basic/basic_commands_CC/cmd_bload_bverify.s b/src/basic/basic_commands_CC/cmd_bload_bverify.s
index a85891f5..2b6db9fb 100644
--- a/src/basic/basic_commands_CC/cmd_bload_bverify.s
+++ b/src/basic/basic_commands_CC/cmd_bload_bverify.s
@@ -39,4 +39,4 @@ cmd_bload:
 
 	// XXX when number parsing is done, change to continue execution
 
-	jmp basic_main_loop
+	jmp shell_main_loop
diff --git a/src/basic/basic_commands_CC/cmd_merge.s b/src/basic/basic_commands_CC/cmd_merge.s
index 5734b68d..bf157798 100644
--- a/src/basic/basic_commands_CC/cmd_merge.s
+++ b/src/basic/basic_commands_CC/cmd_merge.s
@@ -50,4 +50,4 @@ cmd_merge_no_error:
 
 	// XXX when number parsing is done, change to continue execution
 
-	jmp basic_main_loop
+	jmp shell_main_loop
diff --git a/src/basic/basic_delete_line.s b/src/basic/basic_delete_line.s
index 864fd0c7..fdeff539 100644
--- a/src/basic/basic_delete_line.s
+++ b/src/basic/basic_delete_line.s
@@ -3,7 +3,7 @@
 // #LAYOUT# *   *       #IGNORE
 
 // Delete the current BASIC line, which is assumed to have already
-// been found with basic_find_line.
+// been found with find_line.
 // Really only consists of copying memory down.
 // The only complication is that we have to do the copy with ROMs
 // banked out. Oh, yes, and we have to update all the links in
diff --git a/src/basic/basic_find_line.s b/src/basic/editor/find_line.s
similarity index 60%
rename from src/basic/basic_find_line.s
rename to src/basic/editor/find_line.s
index be9a962e..a98cc91c 100644
--- a/src/basic/basic_find_line.s
+++ b/src/basic/editor/find_line.s
@@ -5,19 +5,24 @@
 
 // Find the BASIC line with number LINNUM
 
+// XXX it should be possible to start from the current line (OLDTXT), or from the startup,
+//     depending on the current and target line number
+
+
+find_line:
 
-basic_find_line:
 	// Get pointer to start of BASIC text
 	lda TXTTAB+0
 	sta OLDTXT+0
 	lda TXTTAB+1
 	sta OLDTXT+1
 
-basic_find_line_loop:	
-	// Then search for line number
-	// Line number
-	
-	ldy #3
+	// FALLTROUGH
+
+find_line_loop:
+
+	// Fetch the high byte of line number and compare
+	ldy #$03
 
 #if CONFIG_MEMORY_MODEL_60K
 	ldx #<OLDTXT+0
@@ -30,10 +35,11 @@ basic_find_line_loop:
 
 	cmp LINNUM+1
 	beq !+
-	bcs line_num_too_high
-	bne not_this_line
+	bcs find_line_fail                           // branch if line number too high
+	bne find_line_next
 !:
-	
+
+	// Fetch the low byte of line number and compare
 	dey
 
 #if CONFIG_MEMORY_MODEL_60K
@@ -45,27 +51,23 @@ basic_find_line_loop:
 #endif
 
 	cmp LINNUM+0
-	beq !+
-	bcs line_num_too_high
-	bne not_this_line
-!:
+	beq find_line_success
+	bcs find_line_fail                           // branch if line number too high
+	bne find_line_next
+
+find_line_success:
+
 	clc
 	rts
-not_this_line:
-	// Not this line, so advance to next line
+
+find_line_next:
+
+	// Advance to the next line
+
 	jsr peek_line_pointer_null_check
-	bcs more_lines_exist
+	bcc find_line_fail                           // branch in no more lines exist
 
-	// no more lines exist, return failure
-line_num_too_high:
-	sec
-	rts
-more_lines_exist:	
-
-	// XXX - Add program mangled check here to be triggered
-	// if the link goes backwards.
-	// Follow link to next line
-	ldy #0
+	ldy #$00
 
 #if CONFIG_MEMORY_MODEL_60K
 	ldx #<OLDTXT+0
@@ -76,7 +78,7 @@ more_lines_exist:
 	lda (OLDTXT),y
 #endif
 
-	sta $0100
+	pha
 	iny
 
 #if CONFIG_MEMORY_MODEL_60K
@@ -88,7 +90,16 @@ more_lines_exist:
 #endif
 
 	sta OLDTXT+1
-	lda $0100
+	pla
 	sta OLDTXT+0
 
-	jmp basic_find_line_loop
+#if HAS_OPCODES_65C02
+	bra find_line_loop
+#else
+	jmp find_line_loop
+#endif
+
+find_line_fail:
+
+	sec
+	rts
diff --git a/src/basic/basic_main_loop.s b/src/basic/editor/shell.s
similarity index 64%
rename from src/basic/basic_main_loop.s
rename to src/basic/editor/shell.s
index 06179538..4602dc9b 100644
--- a/src/basic/basic_main_loop.s
+++ b/src/basic/editor/shell.s
@@ -3,7 +3,7 @@
 // #LAYOUT# *   *       #IGNORE
 
 
-basic_main_loop:
+shell_main_loop:
 
 	// Tell user we are ready
 	ldx #IDX__STR_READY
@@ -13,87 +13,104 @@ basic_main_loop:
 	lda #$80
 	jsr JSETMSG
 
-basic_read_next_line:	
+shell_read_next_line:
+
 	// Read a line of input
 	ldx #$00
-read_line_loop:
+!:
 	jsr JCHRIN
-	bcs read_line_loop
+	bcs !-
 	
-	cmp #$0d
-	beq got_line_of_input
+	// Check for RETURN key
+	cmp #$0D
+	beq shell_got_line
+
 	// Not carriage return, so try to append to line so far
 	cpx #80
-	bcs_16 do_STRING_TOO_LONG_error // see Computes Mapping the 64 p93
+	bcs_16 do_STRING_TOO_LONG_error              // see Computes Mapping the 64 p93
 
 	sta BUF,x
 	inx
-	jmp read_line_loop
+	jmp !-
 
-got_line_of_input:
+shell_got_line:
 
 	// Store length of input buffer ready for tokenising
 	stx __tokenise_work1
+	// XXX we should probably store 0 at the end of used BUF
+
+	// FALLTROUGH
+
+shell_strip_leading_spaces:
 
 	// Strip leading spaces from the line
-remove_leading_spaces:
 	lda BUF
 	cmp #$20
-	bne !+
-	ldx #1
-rsl_l1:
+	bne shell_process_line                       // branch if no more leading spaces
+
+	// We have a leading space - strip it away
+	ldx #$01
+!:
 	lda BUF,x
 	sta BUF-1,x
 	inx
 	cpx __tokenise_work1
-	bne rsl_l1
+	bne !-
 
 	// Reduce length of input by one
 	dec __tokenise_work1
+
 	// Stop trying to rim if we run out of input
-	bne remove_leading_spaces
-!:
-	// Do printing of the new line
+	bne shell_strip_leading_spaces
+
+	// FALLTROUGH
+
+shell_process_line:
+
+	// Print a new line
 	jsr print_return
 
 	// Ignore empty lines
 	lda __tokenise_work1
-	beq basic_read_next_line
+	beq shell_read_next_line
 
 	// Check if a wedge should take over
 
 #if CONFIG_DOS_WEDGE || CONFIG_TAPE_WEDGE
 	
-	ldx __tokenise_work1 // here is the size of input
-	
+	ldx __tokenise_work1                         // size of the input, wedges need this  XXX this should not be needed
+
 	// Check if DOS wedge should take over
 	lda BUF
 
 #if CONFIG_DOS_WEDGE
+
 	cmp #$40 // '@'
 	beq_16 wedge_dos
+
 #endif
 #if CONFIG_TAPE_WEDGE
+
 	cmp #$5F // left arrow
 	beq_16 wedge_tape
+
 #endif
 
 #endif
 
-	// Else, tokenise the line
+	// Tokenise the line
 	jsr tokenise_line
 
 	// Has the user entered a line of BASIC beginning with a number?
 	lda BUF
 	cmp #$30
-	bcc not_a_line
+	bcc shell_execute_line
 	cmp #$39
-	bcs not_a_line
+	bcs shell_execute_line
 
-	// Yes, the line begins with a number.
-	// Parse the line number and check validity
+	// Yes, the line begins with a number - parse it and check validity
 
-	// injest_number follows __tokenise_work1 as the offset into the line,
+	// The injest_number follows __tokenise_work1 as the offset into the line,
 	// so remember the line length somewhere else for now.
 	lda __tokenise_work1
 	sta __tokenise_work2
@@ -112,26 +129,30 @@ rsl_l1:
 	lda TXTPTR+0
 	sta __tokenise_work1
 	
-	// Got a valid line number -- so do add/del line
+	// Got a valid line number - we will be adding/deleting a new line
 
 	// Skip any spaces after the line number
 	ldx __tokenise_work1
-skip_spaces:	
+!:
 	lda BUF,x
 	cmp #$20
 	bne !+
 	inx
-	bne skip_spaces
-!:	stx __tokenise_work1
+	bne !-
+!:	
+	stx __tokenise_work1
 
-	// First, clear all variables, so that we only have to shove BASIC text around.
-	// (We could later remove this requirement, and the only effect should be
-	// to slow things down, and that you might have to either CLR if there is no
-	// memory free, or else it would auto CLR when you ran out of program space).
+	// FALLTROUGH
+
+shell_add_delete_line:
+
+	// First, clear all variables, so that we only have to shove BASIC text around
 	jsr basic_do_clr
-
+.break
 	// Delete line if present
-	jsr basic_find_line
+	jsr find_line
+
+// XXX
 
 	bcs !+
 
@@ -147,11 +168,10 @@ skip_spaces:
 	jsr basic_insert_line
 !:
 	// No READY message after entering or deleting a line of BASIC
-	jmp basic_read_next_line
+	jmp shell_read_next_line
 	
-not_a_line:	
 
-	//  Actually interpret the line
+shell_execute_line:	
 
 	// Setup pointer to the statement
 	lda #<BUF
@@ -165,8 +185,7 @@ not_a_line:
 	sta OLDTXT+1
 
 	// Put invalid line number in current line number value,
-	// so that we know we are in direct mode
-	// (Computes Mapping the 64 p19)
+	// so that we know we are in direct mode (Computes Mapping the 64 p19)
 	lda #$FF
 	sta CURLIN+1
 
diff --git a/src/basic/tokenizer/tk_cut_away.s b/src/basic/editor/tk_cut_away.s
similarity index 100%
rename from src/basic/tokenizer/tk_cut_away.s
rename to src/basic/editor/tk_cut_away.s
diff --git a/src/basic/tokenizer/tk_pack.s b/src/basic/editor/tk_pack.s
similarity index 100%
rename from src/basic/tokenizer/tk_pack.s
rename to src/basic/editor/tk_pack.s
diff --git a/src/basic/tokenizer/tk_search.s b/src/basic/editor/tk_search.s
similarity index 100%
rename from src/basic/tokenizer/tk_search.s
rename to src/basic/editor/tk_search.s
diff --git a/src/basic/tokenizer/tk_shorten.s b/src/basic/editor/tk_shorten.s
similarity index 100%
rename from src/basic/tokenizer/tk_shorten.s
rename to src/basic/editor/tk_shorten.s
diff --git a/src/basic/tokenizer/tokenise_line.s b/src/basic/editor/tokenise_line.s
similarity index 100%
rename from src/basic/tokenizer/tokenise_line.s
rename to src/basic/editor/tokenise_line.s
diff --git a/src/basic/engine/do_error.s b/src/basic/engine/do_error.s
index e916f016..e4979e86 100644
--- a/src/basic/engine/do_error.s
+++ b/src/basic/engine/do_error.s
@@ -196,4 +196,4 @@ do_basic_error:                        // error code in .X
 	ldx #$FE
 	txs
 
-	jmp basic_main_loop
+	jmp shell_main_loop
diff --git a/src/basic/engine/execute_line_statements.s b/src/basic/engine/execute_line_statements.s
index 58b10a3d..306c3b2c 100644
--- a/src/basic/engine/execute_line_statements.s
+++ b/src/basic/engine/execute_line_statements.s
@@ -164,7 +164,7 @@ execute_statements_end_of_line:
 
 	ldx CURLIN+1
 	inx
-	beq_16 basic_main_loop
+	beq_16 shell_main_loop
 
 	// Advance to the next line - first copy the line number
 	// to previous line number
@@ -181,7 +181,7 @@ execute_statements_end_of_line:
 
 	lda OLDTXT+0
 	ora OLDTXT+1
-	beq_16 basic_main_loop
+	beq_16 shell_main_loop
 	
 	// FALLTROUGH
 
@@ -191,7 +191,7 @@ execute_line:
 
 	ldy #0
 	jsr peek_line_pointer_null_check
-	bcc_16 basic_main_loop             // branch if end of program reached
+	bcc_16 shell_main_loop             // branch if end of program reached
 
 	// Skip pointer and line number to get address of first statement
 
diff --git a/src/basic/init/basic_warm_start_internal.s b/src/basic/init/basic_warm_start_internal.s
index 75fc68c5..81ff572c 100644
--- a/src/basic/init/basic_warm_start_internal.s
+++ b/src/basic/init/basic_warm_start_internal.s
@@ -27,4 +27,4 @@ basic_warm_start_real:
 	lda CMP0+0
 	jsr print_hex_byte
 !:
-	jmp basic_main_loop
+	jmp shell_main_loop
diff --git a/src/basic/wedge/wedge_dos.s b/src/basic/wedge/wedge_dos.s
index 0e9b5d3d..c8fb1a48 100644
--- a/src/basic/wedge/wedge_dos.s
+++ b/src/basic/wedge/wedge_dos.s
@@ -96,7 +96,7 @@ wedge_dos_change_drive:
 	jmp do_ILLEGAL_DEVICE_NUMBER_error
 !:
 	sta FA
-	jmp basic_main_loop
+	jmp shell_main_loop
 
 wedge_dos_status_get:
 
@@ -238,7 +238,7 @@ wedge_dos_directory_display:
 
 wedge_dos_clean_exit:
 	jsr JCLALL
-	jmp basic_main_loop
+	jmp shell_main_loop
 
 wedge_dos_basic_error:
 	pha