begin implementing BASIC interprettor.

c64/basic/,aliases.s

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+;	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)
+
+	.alias TXTTAB $2B
+	.alias IOSTATUS $90
+	; Keys down clears bits. STOP=bit 7, C= bit 6, SPACE bit 4, CTRL bit 2
+	.alias BUCKYSTATUS $91
+	.alias load_or_verify_flag $93
+	.alias current_file_num $98
+	.alias input_device_number $99
+	; bit 6 = error messages, bit 7 = control messages
+	.alias kernal_message_control_flags $9d
+	.alias jiffy_clock_24bits $a0
+	.alias cassette_buffer_bytes_used $A6
+	.alias load_or_scroll_temp_pointer $AC
+	;; We also use the following for temp colour pointer when scrolling
+	.alias load_save_verify_end_address $AE
+	.alias cassette_buffer_ptr $B2
+	.alias current_filename_length $B7
+	.alias current_logical_filenum $B8
+	.alias current_secondary_address $B9
+	.alias current_device_number $BA
+	.alias current_filename_ptr $BB
+	.alias load_save_start_ptr $C1
+	.alias load_save_end_ptr $C3
+	.alias last_key_matrix_position $C5
+	.alias keys_in_key_buffer $C6
+	.alias reverse_video_flag $C7
+	.alias end_of_input_line $C8
+	.alias start_of_keyboard_input $C9
+	.alias current_key_index_entry $CB
+	.alias cursor_blink_disable $CC
+	.alias cursor_blink_countdown $CD
+	.alias cursor_saved_character $CE
+	.alias cursor_is_visible $CF
+	.alias keyboard_input_ready $D0
+	.alias current_screen_line_ptr $D1
+	.alias current_screen_x $D3
+	.alias quote_mode_flag $D4
+	.alias logical_line_length $D5
+	.alias current_screen_y $D6
+	.alias last_printed_character_ascii $D7
+	.alias insert_mode $D8
+	; Bits 0 -3 = bits 8-11 of screen line address
+	; Bit 7 = line spans multiple physical lines
+	.alias screen_line_link_table $D9
+	.alias current_screen_line_colour_ptr $F3
+	.alias keyboard_decoding_table_ptr $F5
+	.alias rs232_rx_buffer_ptr $F7
+	.alias rs232_tx_buffer_ptr $F9
+
+
+	; "Compute's Mapping the 64" book
+	.alias keyboard_buffer $0277
+	.alias MEMSTR $0281
+	.alias MEMSIZ $0283 	; NOTE: Mapping the 64 erroniously has the hex as $282, while the DEC is correct
+	.alias text_colour $0286 ; p55
+	.alias colour_under_cursor $0287 ; p56
+	.alias HIBASE $0288     ; p56 (high byte of start of screen)
+	.alias key_buffer_size $0289 ; p57
+
+	;; 0 = cursor keys, insert, delete and space repeat, but nothing else
+	;; 128 = all keys repeat
+	;; 64 = no keys repeat
+	.alias key_repeat_flags $028A ; p58
+	;; https://www.c64-wiki.com/wiki/Page_2
+	.alias key_repeat_counter $028B
+	.alias key_first_repeat_delay $028C
+	;; bit 0 = shift, 1 = Vendor Key, 2 = Control
+	.alias key_bucky_state $028D
+	.alias key_last_bucky_state $028E
+	.alias keyboard_decoding_ptr $028F
+	.alias enable_case_switch $0291
+	.alias screen_scroll_disable $0292
+	.alias pal_or_ntsc $02A6

c64/basic/a000.cold_start_vector.s

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+	;; Compute's Mapping the C64 p88
+	.word basic_cold_start
+	

c64/basic/a002.warm_start_vector.s

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+	;; Compute's Mapping the C64 p88
+	.word basic_warm_start

c64/basic/a004.identifier.s

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+	;; Compute's Mapping the 64, p89
+	;; 8 character name
+	;; MEGABAS2 = "MEGA BASIC 2"
+	.byte $4D,$45,$47,$41,$42,$41,$53,$32
+	
+	

c64/basic/basic_cold_start.s

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+	;; BASIC Cold start entry point
+	;; Compute's Mapping the 64 p211
+
+basic_cold_start:	
+	;; Setup BASIC vectors at $0300
+	;; Initialise interpretor
+	;; Print start up message
+	;; jump into warm start loop
+	jmp basic_warm_start
+	
+	

c64/basic/basic_warm_start.s

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+	;; Clear screen etc, show READY prompt.
+
+basic_warm_start:
+	* 	inc $d020
+	jmp -
+