more label conflicts fixed

c64/aliases/,aliases_ram_lowmem.s

@@ -99,7 +99,7 @@
 	.label RIDDATA   = $AA  //          -- NOT IMPLEMENTED --
 	.label RIPRTY    = $AB  //          -- NOT IMPLEMENTED --
 	.label SAL       = $AC  // $AC-$AD  -- NOT IMPLEMENTED -- (implemented screen part)
-	.label EAL       = $AE  // $AE-$AF  -- NOT IMPLEMENTED -- [!] used also byy screen editor
+	.label EAL       = $AE  // $AE-$AF  -- NOT IMPLEMENTED -- [!] used also by screen editor, for temporary color storage when scrolling
 	.label CMP0      = $B0  // $B0-$B1  temporary tape storage, [!] here used for BRK instruction address
 	.label TAPE1     = $B2  // $B2-$B3  tape buffer pointer
 	.label BITTS     = $B4  //          -- NOT IMPLEMENTED --
@@ -124,7 +124,7 @@
 	.label SFDX      = $CB  //          -- NOT IMPLEMENTED --
 	.label BLNSW     = $CC  //          cursor blink disable flag
 	.label BLNCT     = $CD  //          cursor blink countdown
-	.label GDBLN     = $CE  //          cursorb saved character
+	.label GDBLN     = $CE  //          cursor saved character
 	.label BLNON     = $CF  //          cursor visibilityy flag
 	.label CRSW      = $D0  //          whether to input from screen or keyboard
 	.label PNT       = $D1  // $D1-$D2  pointer to the current screen line
@@ -134,7 +134,7 @@
 	.label TBLX      = $D6  //          current screen Y position
 	.label SCHAR     = $D7  //          ASCII value of the last printed character
 	.label INSRT     = $D8  //          insert mode flag/counter
-	.label LDTB1     = $D9  // $D9-$F2  screen line link table, [!] our usage is different  XXX give more details
+	.label LDTBL     = $D9  // $D9-$F2  screen line link table, [!] our usage is different  XXX give more details
 	.label USER      = $F3  // $F3-$F4  pointer to current color RAM location
 	.label KEYTAB    = $F5  // $F5-$F6  -- NOT IMPLEMENTED --
 	.label RIBUF     = $F7  // $F7-$F8  -- NOT IMPLEMENTED --

c64/basic/,aliases.s

@@ -54,41 +54,6 @@
 	.label memmove_dst = $6b
 	.label memmove_size = $6d
 
-	.label current_file_num = $98
-	.label cassette_buffer_bytes_used = $A6
-	.label load_or_scroll_temp_pointer = $AC
-	// We also use the following for temp colour pointer when scrolling
-	.label load_save_verify_end_address = $AE
-
-	.label current_logical_filenum = $B8
-	.label current_secondary_address = $B9
-	.label current_device_number = $BA
-	.label current_filename_ptr = $BB
-	.label load_save_start_ptr = $C1
-	.label load_save_end_ptr = $C3
-	.label last_key_matrix_position = $C5
-	.label keys_in_key_buffer = $C6
-	.label reverse_video_flag = $C7
-	.label end_of_input_line = $C8
-	.label start_of_keyboard_input = $C9
-	.label current_key_index_entry = $CB
-	.label cursor_blink_disable = $CC
-	.label cursor_blink_countdown = $CD
-	.label cursor_saved_character = $CE
-	.label cursor_is_visible = $CF
-	.label keyboard_input_ready = $D0
-	.label current_screen_line_ptr = $D1
-	.label current_screen_x = $D3
-	.label logical_line_length = $D5
-	.label current_screen_y = $D6
-	.label last_printed_character_ascii = $D7
-	.label insert_mode = $D8
-	// Bits 0 -3 = bits 8-11 of screen line address
-	// Bit 7 = line spans multiple physical lines
-	.label screen_line_link_table = $D9
-	.label current_screen_line_colour_ptr = $F3
-	.label keyboard_decoding_table_ptr = $F5
-
 #if CONFIG_MEMORY_MODEL_60K
 
 	// BASIC uses some extra bytes for memory access under ROMs located at $2A7 onwards

c64/basic/cmd_load.s

@@ -37,9 +37,9 @@ cmd_load:
 !:
 	// Filename starts here so set pointer
 	lda basic_current_statement_ptr+0
-	sta current_filename_ptr+0
+	sta FNADDR+0
 	lda basic_current_statement_ptr+1
-	sta current_filename_ptr+1
+	sta FNADDR+1
 
 	// Now search for end of line or closing quote
 	// so that we know the length of the filename
@@ -60,7 +60,7 @@ got_filename:
 
 	// Now fetch the file number, start from the default one
 	jsr select_device
-	stx current_device_number
+	stx FA
 	jsr injest_comma
 	bcs got_devicenumber
 
@@ -70,20 +70,20 @@ got_filename:
 	jmp do_ILLEGAL_QUANTITY_error
 !:
 	lda basic_line_number+0
-	sta current_device_number
+	sta FA
 
 got_devicenumber:
 
 	// Now fetch the secondary address
 	lda #$00
-	sta current_secondary_address
+	sta SA
 	jsr injest_comma
 	bcs got_secondaryaddress
 	jsr basic_parse_line_number
 	lda basic_line_number+1
 	bne !+
 	lda basic_line_number+0
-	sta current_secondary_address
+	sta SA
 	jmp got_secondaryaddress
 !:
 	// Second parameter is above 255, this can't be a secondary address

c64/basic/select_device.s

@@ -11,7 +11,7 @@ select_device:
 
 	// Note: if tape support is introduced here, make sure DOS wedge won't get broken
 
-	ldx current_device_number
+	ldx FA
 	cpx #$08
 	bcs !+
 	ldx #$08

c64/basic/wedge_dos.s

@@ -74,7 +74,7 @@ wedge_dos_change_drive:
 	bcs !+
 	jmp do_ILLEGAL_DEVICE_NUMBER_error
 !:
-	sta current_device_number
+	sta FA
 	jmp basic_end_of_line
 
 wedge_dos_status_get:
@@ -139,7 +139,7 @@ wedge_dos_directory:
 	// First change the secondary address to the one suitable for
 	// directory loading
 	lda #$00 // logical device number
-	ldx current_device_number
+	ldx FA
 	ldy #$60
 	jsr JSETFLS
 

c64/kernal/,aliases.s

@@ -1,43 +1,5 @@
-// Names of ZP and low memory locations
-// (Only those of relevance for the KERNAL)
-// (And only those for now that we feel the need to implement initially)
-// (https://www.c64-wiki.com/wiki/Zeropage)
 
-// XXX get rid of this file, use ,aliases_ram_lowmem.s instead
+// XXX get rid of this file
-
-	.label current_file_num = $98
-	.label input_device_number = DFLTN
-	.label cassette_buffer_bytes_used = $A6
-	.label load_or_scroll_temp_pointer = $AC
-	// We also use the following for temp colour pointer when scrolling
-	.label load_save_verify_end_address = $AE
-	.label current_logical_filenum = $B8
-	.label current_secondary_address = $B9
-	.label current_device_number = $BA
-	.label current_filename_ptr = $BB
-	.label load_save_end_ptr = $C3
-	.label last_key_matrix_position = $C5
-	.label keys_in_key_buffer = $C6
-	.label reverse_video_flag = $C7
-	.label end_of_input_line = $C8
-	.label start_of_keyboard_input = $C9
-	.label current_key_index_entry = $CB
-	.label cursor_blink_disable = $CC
-	.label cursor_blink_countdown = $CD
-	.label cursor_saved_character = $CE
-	.label cursor_is_visible = $CF
-	.label keyboard_input_ready = $D0
-	.label current_screen_line_ptr = $D1
-	.label current_screen_x = $D3
-	.label logical_line_length = $D5
-	.label current_screen_y = $D6
-	.label last_printed_character_ascii = $D7
-	.label insert_mode = $D8
-	// Bits 0 -3 = bits 8-11 of screen line address
-	// Bit 7 = line spans multiple physical lines
-	.label screen_line_link_table = $D9
-	.label current_screen_line_colour_ptr = $F3
-	.label keyboard_decoding_table_ptr = $F5
 
 #if CONFIG_MEMORY_MODEL_60K
 

c64/kernal/blink_cursor.s

@@ -1,15 +1,18 @@
 // We have the following variables:
-// cursor_blink_disable
+// BLNSW (cursor blink switch)
-// cursor_blink_countdown
+// BLNCT (cursor blink countdown)
-// cursor_saved_character
+// GDBLN (cursor saved character)
-// cursor_is_visible
+// BLNON (if cursor is visible)
 // GDCOL (colour under cursor)
+// USER  (current screen line colour pointer)
+// PNT   (current screen line pointer)
+// PNTR  (current screen x position)
 
 show_cursor_if_enabled:
-	lda cursor_blink_disable
+	lda BLNSW
 	beq !+
 	rts
-!:	lda cursor_is_visible
+!:	lda BLNON
 	beq show_cursor
 	rts
 
@@ -17,77 +20,77 @@ show_cursor:
 	// Set cursor as though it had just finished the off phase,
 	// so that the call to blink_cursor paints it
 	lda #$00
-	sta cursor_blink_countdown
+	sta BLNCT
-	sta cursor_is_visible
+	sta BLNON
 	jsr blink_cursor
 	// Then set the timeout to 1 frame, so that the cursor
 	// blinks under key repeat conditions, like on the original KERNAL
 	lda #$01
-	sta cursor_blink_countdown
+	sta BLNCT
 	rts
 
 blink_cursor:
 	// Is the cursor enabled?
-	lda cursor_blink_disable
+	lda BLNSW
 	bne no_blink_cursor
 
 	// Do we need to redraw things?
-	dec cursor_blink_countdown
+	dec BLNCT
 	bpl no_blink_cursor
 
 	// Check if cursor was visible or not, and toggle
-	lda cursor_is_visible
+	lda BLNON
 	bne undraw_cursor
 draw_cursor:
 	jsr calculate_screen_line_pointer
 
-	ldy current_screen_x
+	ldy PNTR
-	lda (current_screen_line_ptr),y
+	lda (PNT),y
-	sta cursor_saved_character	
+	sta GDBLN
 	eor #$80
-	sta (current_screen_line_ptr),y
+	sta (PNT),y
 	// Also set cursor colour
-	lda (current_screen_line_colour_ptr),y
+	lda (USER),y
 	sta GDCOL
 	lda COLOR
-	sta (current_screen_line_colour_ptr),y
+	sta (USER),y
 
 	lda #1
-	sta cursor_is_visible
+	sta BLNON
 
 	jmp reset_blink_timer
 
 undraw_cursor:
 	jsr calculate_screen_line_pointer
 
-	lda cursor_saved_character
+	lda GDBLN
-	ldy current_screen_x
+	ldy PNTR
-	sta (current_screen_line_ptr),y
+	sta (PNT),y
 	lda GDCOL
-	sta (current_screen_line_colour_ptr),y
+	sta (USER),y
 	
 	lda #0
-	sta cursor_is_visible
+	sta BLNON
 	// Fall through
 reset_blink_timer:	
 	// Rest blink counter
 	// (Compute's Mapping the 64, p39-40)
 	lda #20
-	sta cursor_blink_countdown
+	sta BLNCT
 no_blink_cursor:
 	rts
 
 disable_cursor:
 	lda #$80
-	sta cursor_blink_disable
+	sta BLNSW
 	// FALL THROUGH
 hide_cursor_if_visible:
-	lda cursor_is_visible
+	lda BLNON
 	bne undraw_cursor
 	rts
 
 enable_cursor:
 	lda #$00
-	sta cursor_blink_disable
+	sta BLNSW
 	rts
 

c64/kernal/chrin_real.s

@@ -52,18 +52,18 @@ chrin_repeat:
 	// If so, return the next byte, and clear the flag when we reach the end.
 
 	// Do we have a line of input waiting?
-	lda keyboard_input_ready
+	lda CRSW
 	beq read_from_keyboard
 
-	// Yes, we have input waiting at (start_of_keyboard_input)+keyboard_input_ready
+	// Yes, we have input waiting at (LXSP)+CRSW
-	// When keyboard_input_ready = end_of_input_line, then we return a carriage return
+	// When CRSW = INDX, then we return a carriage return
 	// and clear the flag
-	cmp end_of_input_line
+	cmp INDX
 	bne not_end_of_input
 
 	// Return carriage return and clear pending input flag
 	lda #$00
-	sta keyboard_input_ready
+	sta CRSW
 	pla
 	tax
 	clc
@@ -75,9 +75,9 @@ not_end_of_input:
 	tay
 	pla
 	tax
-	lda (start_of_keyboard_input),y
+	lda (LXSP),y
 	jsr screen_code_to_petscii
-	inc keyboard_input_ready
+	inc CRSW
 	clc
 	rts
 
@@ -87,7 +87,7 @@ read_from_keyboard:
 	jsr enable_cursor
 	
 	// Wait for a key
-	lda keys_in_key_buffer
+	lda NDX
 	beq chrin_repeat
 
 	lda KEYD
@@ -106,10 +106,10 @@ read_from_keyboard:
 	// (Compute's Mapping the 64, p96)
 
 	// Set pointer to line of input
-	lda current_screen_line_ptr+0
+	lda PNT+0
-	sta start_of_keyboard_input+0
+	sta LXSP+0
-	lda current_screen_line_ptr+1
+	lda PNT+1
-	sta start_of_keyboard_input+1
+	sta LXSP+1
 
 	// Calculate length
 	jsr get_current_line_logical_length
@@ -117,18 +117,18 @@ read_from_keyboard:
 	iny
 !:	dey
 	bmi empty_line
-	lda (current_screen_line_ptr),y
+	lda (PNT),y
 	cmp #$20
 	beq !-
 	iny
-	sty end_of_input_line
+	sty INDX
 	lda #$01
-	sta keyboard_input_ready
+	sta CRSW
 	// Return first char of line
 	ldy #$00
 	pla
 	tax
-	lda (start_of_keyboard_input),y
+	lda (LXSP),y
 	jsr screen_code_to_petscii
 	clc
 	rts
@@ -166,7 +166,7 @@ pop_keyboard_buffer:
 	iny
 	cpy XMAX
 	bne !-
-	dec keys_in_key_buffer
+	dec NDX
 	cli
 
 	rts

c64/kernal/chrout_real.s

@@ -11,7 +11,7 @@
 
 chrout_real:
 
-	sta last_printed_character_ascii
+	sta SCHAR
 
 	// Save X and Y values
 	// (Confirmed by writing a test program that X and Y
@@ -34,7 +34,7 @@ chrout_real:
 
 chrout_iec:
 
-	lda last_printed_character_ascii
+	lda SCHAR
 	jsr JCIOUT
 	bcc chrout_done
 
@@ -77,7 +77,7 @@ chrout_done:
 	tay
 	pla
 	tax
-	lda last_printed_character_ascii
+	lda SCHAR
 	clc // indicate success
 	rts
 
@@ -88,7 +88,7 @@ chrout_screen:
 
 	jsr hide_cursor_if_visible
 
-	lda last_printed_character_ascii
+	lda SCHAR
 	tax
 
 	// Check for special characters
@@ -111,7 +111,7 @@ not_0a:
 	// RETURN clears quote and insert modes
 	lda #$00
 	sta QTSW
-	sta insert_mode
+	sta INSRT
 	jmp screen_advance_to_next_line
 not_0d:
 
@@ -125,7 +125,7 @@ not_0d:
 	cmp #79
 	bne definitely_not_too_long
 	tay
-	lda (current_screen_line_ptr),y
+	lda (PNT),y
 	cmp #$20
 	beq definitely_not_too_long
 
@@ -135,7 +135,7 @@ not_0d:
 definitely_not_too_long:
 	// Work out if line needs to be expanded, and if so expand it
 	ldy #39
-	lda (current_screen_line_ptr),y
+	lda (PNT),y
 	cmp #$20
 	beq no_need_to_extend
 
@@ -155,89 +155,89 @@ no_need_to_extend:
 	// though we really don't believe that the routine can be copyrighted
 	// due to the lack of creativity.
 	dey
-	lda (current_screen_line_colour_ptr),y
+	lda (USER),y
 	iny
-	sta (current_screen_line_colour_ptr),y
+	sta (USER),y
 	dey
-	lda (current_screen_line_ptr),y
+	lda (PNT),y
 	iny
-	sta (current_screen_line_ptr),y
+	sta (PNT),y
 
 	dey
-	cpy current_screen_x
+	cpy PNTR
 	bne !-
 
 	// Increase insert mode count (which causes quote-mode like behaviour)
-	inc insert_mode
+	inc INSRT
 
 	// Put space in the inserted gap
 	lda #$20
-	sta (current_screen_line_ptr),y
+	sta (PNT),y
 
 	jmp chrout_done
 not_94:	
 
 	// DELETE in insert mode embeds control character
-	ldx insert_mode
+	ldx INSRT
 	bne not_14
 
 	cmp #$14
 	bne not_14
 
 	// Delete
-	ldx current_screen_x
+	ldx PNTR
 	bne delete_non_zero_column
 delete_at_column_0:
-	ldy current_screen_y
+	ldy TBLX
 	bne not_row_0
 	// delete from row 0, col 0 does nothing
 	jmp chrout_done
 not_row_0:
 	// Column 0 delete just moves us to the end of the
 	// previous line, without actually deleting anything
-	dec current_screen_y
+	dec TBLX
 	jsr get_current_line_logical_length
-	lda logical_line_length
+	lda LNMX
 
-	sta current_screen_x
+	sta PNTR
 	jsr calculate_screen_line_pointer
 	jmp chrout_done
 
 delete_non_zero_column:
 	// Copy rest of line down
 	jsr get_current_line_logical_length
-	ldy current_screen_x
+	ldy PNTR
-	cpy logical_line_length
+	cpy LNMX
 	beq done_delete
 	dey
 !:
 	iny
-	lda (current_screen_line_ptr),y
+	lda (PNT),y
 	dey
-	sta (current_screen_line_ptr),y
+	sta (PNT),y
 	iny
-	lda (current_screen_line_colour_ptr),y
+	lda (USER),y
 	dey
-	sta (current_screen_line_colour_ptr),y
+	sta (USER),y
 	iny
-	cpy logical_line_length
+	cpy LNMX
 	bne !-
 
 	// Clear char at end of line
 	jsr get_current_line_logical_length
 	tay
 	lda #$20
-	sta (current_screen_line_ptr),y
+	sta (PNT),y
 
 done_delete:
-	dec current_screen_x
+	dec PNTR
 	jmp chrout_done
 not_14:
 
 	// Check for quote mode
 	ldx QTSW
 	bne is_quote_mode
-	ldx insert_mode
+	ldx INSRT
 	bne is_quote_mode
 	jmp not_quote_mode
 
@@ -283,24 +283,24 @@ colour_check_loop:
 	cmp #$12
 	bne not_12
 	lda #$80
-	sta reverse_video_flag
+	sta RVS
 	jmp chrout_done
 not_12:
 	// Compute's Mapping the 64 p 38	
 	cmp #$92
 	bne not_92
 	lda #$00
-	sta reverse_video_flag
+	sta RVS
 	jmp chrout_done
 not_92:
 
 	// Check for cursor movement keys
 	cmp #$11
 	bne not_11
-	lda current_screen_x
+	lda PNTR
 	clc
 	adc #40
-	sta current_screen_x
+	sta PNTR
 	// We need to advance the pointer manually, as normalising
 	// now will break things. The pointer update is required
 	// so that we can tell if we really are on the bottom phys
@@ -311,22 +311,22 @@ not_92:
 not_11:
 	cmp #$1d
 	bne not_1d
-	inc current_screen_x
+	inc PNTR
 	jsr calculate_screen_line_pointer
 	jmp chrout_done
 not_1d:
 	cmp #$91
 	bne not_91
-	lda current_screen_x
+	lda PNTR
 	sec
 	sbc #40
-	sta current_screen_x
+	sta PNTR
 	jsr calculate_screen_line_pointer
 	jmp chrout_done
 not_91:
 	cmp #$9d
 	bne not_9d
-	dec current_screen_x
+	dec PNTR
 	jsr calculate_screen_line_pointer
 	jmp chrout_done
 not_9d:
@@ -335,8 +335,8 @@ not_9d:
 	cmp #$13
 	bne not_13
 	lda #0
-	sta current_screen_x
+	sta PNTR
-	sta current_screen_y
+	sta TBLX
 	jsr calculate_screen_line_pointer
 	jmp chrout_done
 not_13:	
@@ -401,14 +401,14 @@ output_literal_char:
 
 	pha
 	
-	ldy current_screen_x
+	ldy PNTR
-	ora reverse_video_flag	// Compute's Mapping the 64  p38
+	ora RVS    // Compute's Mapping the 64  p38
-	sta (current_screen_line_ptr),y
+	sta (PNT),y
 
 	// Decrement number of chars waiting to be inserted
-	lda insert_mode
+	lda INSRT
 	beq !+
-	dec insert_mode
+	dec INSRT
 !:	
 	pla
 	cmp #$22
@@ -423,36 +423,36 @@ not_quote:
 
 	// Set colour
 	lda COLOR
-	sta (current_screen_line_colour_ptr),y
+	sta (USER),y
 
 	// Advance the column, and scroll screen down if we need
 	// to insert a 2nd line in this logical line.
 	// (eg Compute's Mapping the 64 p41)
-	ldx current_screen_y
+	ldx TBLX
 	iny
-	sty current_screen_x
+	sty PNTR
 	cpy #40
 	bne !+
 	jsr screen_grow_logical_line
-	ldy current_screen_x
+	ldy PNTR
 !:
 	cpy #80
 	bcc no_screen_advance_to_next_line
 	lda #0
-	sta current_screen_x
+	sta PNTR
 	jmp screen_advance_to_next_line
 no_screen_advance_to_next_line:
 	jmp chrout_done
 
 screen_grow_logical_line:
-	ldy current_screen_y
+	ldy TBLX
 	// Don't grow line if it is already grown
-	lda screen_line_link_table,y
+	lda LDTBL,y
 	bpl !+
 	jmp done_grow_line
 !:
 	lda #$80
-	sta screen_line_link_table,y
+	sta LDTBL,y
 
 	// Now make space for the extra line added.
 	// If we are on the last physical line of the screen,
@@ -471,11 +471,11 @@ screen_grow_logical_line:
 	ldy #0
 count_rows_loop:
 	dex
-	lda screen_line_link_table,y
+	lda LDTBL,y
 	bpl !+
 	dex
 !:	iny
-	cpy current_screen_y
+	cpy TBLX
 	bne count_rows_loop
 
 	cpx #0
@@ -493,28 +493,28 @@ count_rows_loop:
 	lda HIBASE
 	clc
 	adc #3
-	sta current_screen_line_ptr+1
+	sta PNT+1
-	sta load_or_scroll_temp_pointer+1
+	sta SAL+1
 	lda #>$DBC0
-	sta load_save_verify_end_address+1
+	sta EAL+1
-	sta current_screen_line_colour_ptr+1
+	sta USER+1
 
 	lda #<$03C0
-	sta current_screen_line_ptr+0
+	sta PNT+0
-	sta current_screen_line_colour_ptr+0
+	sta USER+0
 	//  souce address is line above
 	sec
 	sbc #40
-	sta load_or_scroll_temp_pointer+0
+	sta SAL+0
-	sta load_save_verify_end_address+0
+	sta EAL+0
 
 copy_line_down_loop:
 	ldy #39
 cl_inner:
-	lda (load_save_verify_end_address),y
+	lda (EAL),y
-	sta (current_screen_line_colour_ptr),y
+	sta (USER),y
-	lda (load_or_scroll_temp_pointer),y
+	lda (SAL),y
-	sta (current_screen_line_ptr),y
+	sta (PNT),y
 	dey
 	bpl cl_inner
 
@@ -523,29 +523,29 @@ cl_inner:
 
 	// Old source is new destination
 	// Use different registers to minimise byte similarity with C64 KERNAl
-	ldy load_or_scroll_temp_pointer+1
+	ldy SAL+1
-	sty current_screen_line_ptr+1
+	sty PNT+1
-	lda load_save_verify_end_address+1
+	lda EAL+1
-	ldy load_or_scroll_temp_pointer+0
+	ldy SAL+0
-	sta current_screen_line_colour_ptr+1
+	sta USER+1
-	sty current_screen_line_ptr+0
+	sty PNT+0
-	sty current_screen_line_colour_ptr+0
+	sty USER+0
 	
 	// Decrementing source pointers
-	lda load_or_scroll_temp_pointer+0
+	lda SAL+0
 	sec
 	sbc #<40
-	sta load_or_scroll_temp_pointer+0
+	sta SAL+0
-	sta load_save_verify_end_address+0
+	sta EAL+0
-	lda load_or_scroll_temp_pointer+1
+	lda SAL+1
 	sbc #>40
-	sta load_or_scroll_temp_pointer+1
+	sta SAL+1
 	// convert to screen equivalent
 	sec
 	sbc HIBASE
 	clc
 	adc #>$D800
-	sta load_save_verify_end_address+1
+	sta EAL+1
 
 	dex
 	bne copy_line_down_loop
@@ -557,9 +557,9 @@ no_copy_down:
 	ldy #79
 !:
 	lda COLOR
-	sta (current_screen_line_colour_ptr),y
+	sta (USER),y
 	lda #$20
-	sta (current_screen_line_ptr),y
+	sta (PNT),y
 	dey
 	cpy #40
 	bne !-
@@ -575,23 +575,23 @@ scroll_up_if_on_last_line:
 	// Colour RAM is always in fixed place, so is easiest
 	// to use to check if we are on the last line.
 	// The last line is at $D800 + 24*40 = $DBC0
-	lda current_screen_line_colour_ptr+1
+	lda USER+1
 	cmp #>$DBC0
 	bne not_last_line
 
-	lda current_screen_line_colour_ptr+0
+	lda USER+0
 	cmp #<$DBC0
 	beq is_last_line
 
 	jsr get_current_line_logical_length
 	clc
-	adc current_screen_line_colour_ptr+0
+	adc USER+0
 	cmp #<$DBE7-1
 	bcc not_last_line
 
 is_last_line:
 
-	dec current_screen_y
+	dec TBLX
 
 	// FALL THROUGH
 
@@ -601,68 +601,68 @@ scroll_screen_up:
 
 	// Get pointers to start of screen + colour RAM
 	lda HIBASE
-	sta current_screen_line_ptr+1
+	sta PNT+1
-	sta load_or_scroll_temp_pointer+1
+	sta SAL+1
 	lda #>$D800
-	sta current_screen_line_colour_ptr+1
+	sta USER+1
-	sta load_save_verify_end_address+1
+	sta EAL+1
 	lda #$00
-	sta current_screen_line_ptr+0
+	sta PNT+0
-	sta current_screen_line_colour_ptr+0
+	sta USER+0
 	
 	//  Get pointers to screen/colour RAM source
-	lda screen_line_link_table+0
+	lda LDTBL+0
 	bmi !+
 	lda #40
 	.byte $2C 		// BIT $nnnn to skip next instruction
 !:
 	lda #80
-	sta load_or_scroll_temp_pointer+0
+	sta SAL+0
-	sta load_save_verify_end_address+0
+	sta EAL+0
 
 	//  Copy first three pages
 	ldy #$00
 	ldx #3
 scroll_copy_loop:
-	lda (load_save_verify_end_address),y
+	lda (EAL),y
-	sta (current_screen_line_colour_ptr),y
+	sta (USER),y
-	lda (load_or_scroll_temp_pointer),y
+	lda (SAL),y
-	sta (current_screen_line_ptr),y
+	sta (PNT),y
 
 	iny
 	bne scroll_copy_loop
 
-	inc load_or_scroll_temp_pointer+1
+	inc SAL+1
-	inc current_screen_line_ptr+1
+	inc PNT+1
-	inc load_save_verify_end_address+1
+	inc EAL+1
-	inc current_screen_line_colour_ptr+1
+	inc USER+1
 	dex
 	bne scroll_copy_loop
 
 	// Copy last partial page
 	// We need to copy 1000-(3*256)-line length
 	// = 232 - line length
-	lda load_or_scroll_temp_pointer+0
+	lda SAL+0
 	lda #232
 	sec
-	sbc load_or_scroll_temp_pointer+0
+	sbc SAL+0
 	tax
 scroll_copy_loop2:
- 	lda (load_save_verify_end_address),y
+ 	lda (EAL),y
- 	sta (current_screen_line_colour_ptr),y
+ 	sta (USER),y
- 	lda (load_or_scroll_temp_pointer),y
+ 	lda (SAL),y
- 	sta (current_screen_line_ptr),y
+ 	sta (PNT),y
  	iny
  	dex
  	bne scroll_copy_loop2
 
 	// Fill in scrolled up area
-	ldx load_or_scroll_temp_pointer+0
+	ldx SAL+0
 scroll_copy_loop3:
 	lda COLOR
-	sta (current_screen_line_colour_ptr),y
+	sta (USER),y
 	lda #$20
-	sta (current_screen_line_ptr),y
+	sta (PNT),y
 	iny
 	dex
 	bne scroll_copy_loop3
@@ -671,13 +671,13 @@ scroll_copy_loop3:
 	ldy #0
 	ldx #24
 link_copy:
-	lda screen_line_link_table+1,y
+	lda LDTBL+1,y
-	sta screen_line_link_table+0,y
+	sta LDTBL+0,y
 	iny
 	dex
 	bne link_copy
 	// Clear line link flag of last line
-	stx screen_line_link_table+24
+	stx LDTBL+24
 
 	// Restore correct line pointers
 	jsr calculate_screen_line_pointer
@@ -685,14 +685,14 @@ link_copy:
 	rts
 
 get_current_line_logical_length:
-	ldy current_screen_y
+	ldy TBLX
-	lda screen_line_link_table,y
+	lda LDTBL,y
 	bpl line_not_linked_del
 	lda #79
 	.byte $2c 		// BIT absolute mode, which we use to skip the next two instruction bytes
 line_not_linked_del:
 	lda #39
-	sta logical_line_length
+	sta LNMX
 	rts
 
 screen_advance_to_next_line:
@@ -701,37 +701,37 @@ screen_advance_to_next_line:
 	
 	//  Go to start of line
 	lda #0
-	sta current_screen_x
+	sta PNTR
 	//  Advance line number
-	ldy current_screen_y
+	ldy TBLX
 
 	// Do quick fix to line pointer to work out if it is off
 	// the bottom of the screen.
 	ldx #40
-	lda screen_line_link_table,y
+	lda LDTBL,y
 	bmi !+
 	.byte $2c
 !:	ldx #80
 	txa
 	clc
-	adc current_screen_line_ptr+0
+	adc PNT+0
-	sta current_screen_line_ptr+0
+	sta PNT+0
-	lda current_screen_line_ptr+1
+	lda PNT+1
 	adc #0
-	sta current_screen_line_ptr+1
+	sta PNT+1
 
-	inc current_screen_y
+	inc TBLX
 
 	// Check if it will trigger scrolling
 	// Work out if we have gone off the bottom of the screen?
 	// 1040 > 1024, so if high byte of screen pointer is >= (HIBASE+4),
 	// then we are off the bottom of the screen
-	lda current_screen_line_ptr+1
+	lda PNT+1
 	sec
 	sbc HIBASE
 	cmp #3
 	bcc !+
-	lda current_screen_line_ptr+0
+	lda PNT+0
 	cmp #$e7
 	bcc !+
 
@@ -744,83 +744,82 @@ screen_advance_to_next_line:
 	jmp chrout_done
 
 add_40_to_screen_x:
-	lda current_screen_x
+	lda PNTR
 	clc
 	adc #40
-	sta current_screen_x
+	sta PNTR
 	rts
 
 normalise_screen_x_y:	
 	// Normalise X and Y values
 
 	// If X < 0, then make X = X + 40 (or 80, if previous line is linked)
-!:	lda current_screen_x
+!:	lda PNTR
 	bpl x_not_negative
-	dec current_screen_y
+	dec TBLX
 	// Check that we didn't go backwards off the top of the screen
 	bpl !+
 	lda #0
-	sta current_screen_y
+	sta TBLX
 
 !:	jsr add_40_to_screen_x
 
 	// Check if line is linked, if so, add 40 again
-	ldy current_screen_y
+	ldy TBLX
-	lda screen_line_link_table,y
+	lda LDTBL,y
 	bpl !+
 	jsr add_40_to_screen_x
 !:
 
 x_not_negative:
 	// Work out if X is too big
-	ldy current_screen_y
+	ldy TBLX
-	lda screen_line_link_table,y
+	lda LDTBL,y
 	bpl !+
 	lda #79
 	.byte $2C 		// BIT $nnnn, used to skip next instruction
 !:	lda #39
-	cmp current_screen_x
+	cmp PNTR
 	bcs x_not_too_big
 
 	// X value is too big, so subtract 40 and increment Y
-	lda current_screen_x
+	lda PNTR
 	sec
 	sbc #40
-	sta current_screen_x
+	sta PNTR
-	inc current_screen_y
+	inc TBLX
 
 x_not_too_big:
 
 	// Make sure Y isn't negative
-	lda current_screen_y
+	lda TBLX
 	bpl !+
 	lda #0
-	sta current_screen_y
+	sta TBLX
 !:
 	// Make sure Y isn't too large for absolute size of
 	// screen
 	cmp #24
 	bcc !+
 	lda #24
-	sta current_screen_y
+	sta TBLX
 !:
 	// Make sure Y isn't too much for the screen, taking
 	// into account the line link table
 	ldy #24 		// max allowable line
 	ldx #0
 link_count_loop:
-	lda screen_line_link_table,x
+	lda LDTBL,x
 	bpl !+
 	dey
 !:	inx
 	cpx #25
 	bne link_count_loop
 	tya
-	cmp current_screen_y
+	cmp TBLX
 	bcs y_ok
-	sta current_screen_y
+	sta TBLX
 y_ok:
-	
 	rts
 
 calculate_screen_line_pointer:
@@ -828,12 +827,12 @@ calculate_screen_line_pointer:
 	
 	//  Reset pointer to start of screen
 	lda HIBASE
-	sta current_screen_line_ptr+1
+	sta PNT+1
 	lda #0
-	sta current_screen_line_ptr+0
+	sta PNT+0
 
 	// Add 40 for every line, or 80 if the lines are linked
-	ldx current_screen_y
+	ldx TBLX
 
 !:
 	// Stop if we have counted enough lines
@@ -844,18 +843,18 @@ calculate_screen_line_pointer:
 	ldy #40
 	// -1 offset is because we count down from N to 1, not
 	// N-1 to 0.
-	lda screen_line_link_table-1,x
+	lda LDTBL-1,x
 	bpl cslp_l1
 	ldy #80
 cslp_l1:
 	// Add computed line length to pointer value
 	tya
 	clc
-	adc current_screen_line_ptr+0
+	adc PNT+0
-	sta current_screen_line_ptr+0
+	sta PNT+0
-	lda current_screen_line_ptr+1
+	lda PNT+1
 	adc #0
-	sta current_screen_line_ptr+1
+	sta PNT+1
 	
 	// Loop back to next line
 	dex
@@ -866,36 +865,36 @@ cslp_l1:
 
 update_colour_line_pointer:
 	// Now setup pointer to colour RAM
-	lda current_screen_line_ptr+0
+	lda PNT+0
-	sta current_screen_line_colour_ptr+0
+	sta USER+0
-	lda current_screen_line_ptr+1
+	lda PNT+1
 	sec
 	sbc HIBASE
 	clc
 	adc #>$d800
-	sta current_screen_line_colour_ptr+1
+	sta USER+1
 
 	rts
 
 
 advance_screen_pointer_40_bytes:
-	lda current_screen_line_ptr+0
+	lda PNT+0
 	clc
 	adc #<40
-	sta current_screen_line_ptr+0
+	sta PNT+0
-	sta current_screen_line_colour_ptr+0
+	sta USER+0
-	lda current_screen_line_ptr+1
+	lda PNT+1
 	adc #>40
-	sta current_screen_line_ptr+1
+	sta PNT+1
 	sec
 	sbc HIBASE
 	clc
 	adc #>$D800
-	sta current_screen_line_colour_ptr+1
+	sta USER+1
 
 	jmp update_colour_line_pointer
 
-colour_codes:
+colour_codes: // consider moving them to separate location
 	// CHR$ codes for the 16 colours
 	.byte 144,5,28,159,156,30,31,158
 	.byte 129,149,150,151,152,153,154,155

c64/kernal/cint_real.s

@@ -69,7 +69,7 @@ cint_brk: // entry for BRK and STOP+RESTORE - XXX, where should it start?
 
 	// Initialise cursor blink flags  (Compute's Mapping the 64 p215)
 	lda #$00
-	sta cursor_blink_disable
+	sta BLNSW
 
 	// Set keyboard decode vector  (Compute's Mapping the 64 p215)
 

c64/kernal/e544.clear_screen.s

@@ -9,7 +9,7 @@ clear_screen:
 	lda #$00
 	ldy #24
 clearscreen_l1:
-	sta screen_line_link_table,y
+	sta LDTBL,y
 	dey
 	bpl clearscreen_l1
 
@@ -19,28 +19,28 @@ clearscreen_l1:
 	// We should do this at HIBASE, which annoyingly
 	// is no ZP, so we need to make a vector
 	// (Compute's Mapping the 64 p216)
-	// Get pointer to the screen into current_screen_line_ptr
+	// Get pointer to the screen into PNT
 	// as it is the first appropriate place for it found when
 	// searching through the ZP allocations listed in
 	// Compute's Mapping the 64
-	sta current_screen_line_ptr+0
+	sta PNT+0
 	lda HIBASE
-	sta current_screen_line_ptr+1
+	sta PNT+1
 	ldx #$03		// countdown for pages to update
 	iny 			// Y now = #$00
 	lda #$20		// space character
 clearscreen_l2:
-	sta (current_screen_line_ptr),y
+	sta (PNT),y
 	iny
 	bne clearscreen_l2
 	// To draw only 1000 bytes, add 250 to address each time
-	lda current_screen_line_ptr
+	lda PNT
 	clc
 	adc #<250
-	sta current_screen_line_ptr
+	sta PNT
-	lda current_screen_line_ptr+1
+	lda PNT+1
 	adc #>250
-	sta current_screen_line_ptr+1
+	sta PNT+1
 	lda #$20		// get space character again
 	dex
 	bpl clearscreen_l2

c64/kernal/f13e.getin.s

@@ -13,7 +13,7 @@
 GETIN:
 
 	// Wait for a key
-	lda keys_in_key_buffer
+	lda NDX
 	bne !+
 
 	// Nothing in keyboard buffer to read

c64/kernal/f34a.open.s

@@ -20,7 +20,7 @@ OPEN:
 	beq !+
 	dey
 	lda LAT, y
-	cmp current_logical_filenum
+	cmp LA
 	bne open_not_yet_open
 	jmp kernalerror_FILE_ALREADY_OPEN
 open_not_yet_open:
@@ -43,11 +43,11 @@ open_has_space:
 	// LAT / FAT / SAT support implemented according to
 	// 'Compute's Mapping the Commodore 64', page 52
 
-	lda current_logical_filenum
+	lda LA
 	sta LAT, y
-	lda current_device_number
+	lda FA
 	sta FAT, y
-	lda current_secondary_address
+	lda SA
 	sta SAT, y
 
 	iny
@@ -58,7 +58,7 @@ open_has_space:
 	beq open_done_success
 	
 	// Check for IEC device
-	lda current_device_number
+	lda FA
 	jsr iec_check_devnum
 	bcc open_iec
 
@@ -75,7 +75,7 @@ open_iec:
 	bcc !+
 	jmp kernalerror_DEVICE_NOT_FOUND
 !:
-	lda current_secondary_address
+	lda SA
 	jsr iec_cmd_open
 	bcc !+
 	jmp kernalerror_DEVICE_NOT_FOUND

c64/kernal/f4a5.load.s

@@ -40,7 +40,7 @@ LOAD:
 	TARGET_HOOK_LOAD()
 
 	// Check whether we support the requested device
-	lda current_device_number
+	lda FA
 	and #$FC
 	bne !+
 	jmp lvs_illegal_device_number // device number below 4, not an IEC device
@@ -60,7 +60,7 @@ LOAD:
 	// in the C64, only in the drive.
 
 	// Call device to LISTEN (p16)
-	lda current_device_number
+	lda FA
 	jsr LISTEN
 	bcc !+
 	jmp lvs_device_not_found_error // XXX deduplicate with other jumps in this routine
@@ -77,7 +77,7 @@ LOAD:
 	jmp lvs_load_verify_error // XXX deduplicate with other jumps in this routine 
 !:
 	// Now command device to talk (p16)
-	lda current_device_number
+	lda FA
 	jsr TALK
 	bcc !+
 	jmp lvs_load_verify_error // XXX deduplicate with other jumps in this routine 
@@ -99,7 +99,7 @@ LOAD:
 	bcc !+
 	jmp lvs_file_not_found_error // XXX deduplicate with other jumps in this routine
 !:
-	ldx current_secondary_address
+	ldx SA
 	beq !+
 	sta STAL+0
 !:
@@ -107,7 +107,7 @@ LOAD:
 	bcc !+
 	jmp lvs_file_not_found_error // XXX deduplicate with other jumps in this routine
 !:
-	ldx current_secondary_address
+	ldx SA
 	beq !+
 	sta STAL+1
 !:
@@ -140,7 +140,7 @@ load_loop:
 
 	// Close file on drive
 
-	lda current_device_number
+	lda FA
 	jsr close_load
 
 	// Return last address

c64/kernal/home_cursor.s

@@ -4,7 +4,7 @@
 home_cursor:
 
 	lda #$00
-	sta current_screen_x
+	sta PNTR // x position
-	sta current_screen_y
+	sta TBLX // y position
 
 	jmp set_pointer_to_current_screen_line

c64/kernal/lvs_helpers.s

@@ -10,10 +10,10 @@ lvs_send_file_name_loop:
 	beq lvs_send_file_name_done
 
 #if CONFIG_MEMORY_MODEL_60K
-	ldx #<current_filename_ptr+0
+	ldx #<FNADDR+0
 	jsr peek_under_roms
 #else // CONFIG_MEMORY_MODEL_38K
-	lda (current_filename_ptr),y
+	lda (FNADDR),y
 #endif
 
 	iny
@@ -81,10 +81,10 @@ lvs_display_searching_for:
 	beq lvs_display_end
 
 #if CONFIG_MEMORY_MODEL_60K
-	ldx #<current_filename_ptr+0
+	ldx #<FNADDR+0
 	jsr peek_under_roms
 #else // CONFIG_MEMORY_MODEL_38K
-	lda (current_filename_ptr),y
+	lda (FNADDR),y
 #endif
 
 	jsr JCHROUT

c64/kernal/plot.s

@@ -12,15 +12,15 @@ PLOT:
 	bcs plot_get
 
 plot_set:
-	sty current_screen_y
+	sty TBLX
-	stx current_screen_x
+	stx PNTR
 
 	// XXX handle cursor blink
 
 	// FALLTROUGH to save one byte on RTS
 
 plot_get:
-	ldy current_screen_y
+	ldy TBLX
-	ldx current_screen_x
+	ldx PNTR
 	rts
 

c64/kernal/readst.s

@@ -12,7 +12,7 @@ READST:
 
 	// Check the current device number
 
-	lda current_device_number
+	lda FA
 	cmp #$02
 	bne !+
 	

c64/kernal/scnkey.s

@@ -122,17 +122,16 @@ accept_key:
 	beq sk_nokey
 
 	// Stash key into keyboard buffer
-	ldx keys_in_key_buffer
+	ldx NDX
 	cpx XMAX
 	beq sk_nokey
 	sta KEYD,x
-	inc keys_in_key_buffer
+	inc NDX
 
 sk_nokey:
 
 	rts
 
-
 	// //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 	// // Routine for Scanning a Matrix Row
 
@@ -181,13 +180,12 @@ OverFlow:
 	pla
 	// Don't manipulate last legal buffer as the routine will fix itself once it gets valid input again.
 
-TooManyNewKeys:
 ReturnNoKeys:
 	sec
 	lda #$00
 	sta BufferQuantity
 	lda #$FF
-	sta last_key_matrix_position
+	sta LSTX
 	ldx #MaxKeyRollover-1
 !:
 	sta Buffer,x
@@ -463,7 +461,7 @@ RecordKeypress:
 	ldy BufferQuantity
 	cpy #MaxKeyRollover
 	bcc !+
-	jmp TooManyNewKeys
+	jmp ReturnNoKeys // too many new keys
 !:
 AcceptKeyEvent:	
     sta Buffer,y
@@ -488,7 +486,7 @@ ConsiderNextKey:
 
 KeyHeld:
 	// The key in A is still held down.
-	// compare with key in last_key_matrix_position
+	// compare with key in LSTX
 	// (Compute's Mapping the 64 p36-37)
 	// if different, reset repeat count down.
 
@@ -503,11 +501,11 @@ KeyHeld:
 	cmp #61
 	beq BuckyHeld
 
-	cmp last_key_matrix_position
+	cmp LSTX
 	beq SameKeyHeld
 
 	// Different key held
-	sta last_key_matrix_position
+	sta LSTX
 	pha
 	lda DELAY
 	sta KOUNT

c64/kernal/set_pointer_to_current_screen_line.s

@@ -1,32 +1,32 @@
 	// Put the address of the screen current line
-	// into the pointer at $D1 (current_screen_line_ptr).
+	// into the pointer at $D1 (PNT).
 	// It must take into account the screen line link table
 	// (Compute's Mapping the 64 p216)
 set_pointer_to_current_screen_line:
 	//  Get pointer to start of the screen
 	lda HIBASE
-	sta current_screen_line_ptr+1
+	sta PNT+1
 	lda #$00
-	sta current_screen_line_ptr+0
+	sta PNT+0
 
 	// Now advance for the number of lines
-	ldx current_screen_y
+	ldx TBLX
 
 sptcsl_l2:
 	// XXX - Should we read the columns per line from
 	// somewhere?
 	ldy #<40
 	// Double line length if line is linked
-	lda screen_line_link_table,x
+	lda LDTBL,x
 	bpl sptcsl_l1
 	ldy #<80
 sptcsl_l1:
 	tya
 	clc
-	adc current_screen_line_ptr+0
+	adc PNT+0
-	lda current_screen_line_ptr+1
+	lda PNT+1
 	adc #>40
-	sta current_screen_line_ptr+1
+	sta PNT+1
 
 	dex
 	bpl sptcsl_l2

c64/kernal/setfls.s

@@ -13,8 +13,8 @@ SETFLS:
 	// There are 6 sane ways to implement this routine,
 	// I hope this one won't cause similarity to CBM code
 
-	sta current_logical_filenum
+	sta LA
-	sty current_secondary_address
+	sty SA
-	stx current_device_number
+	stx FA
 
 	rts