VIC-20 / Commodore 64 SuperChart

This table appears in The Complete Commodore Inner Space Anthology, pages 37 and 38. The data are rearranged here to best suit the format of a webpage, and a couple of pretty big errors in the Inner Space Anthology listing have been corrected. Corrections are noted below each block.

It is called a SuperChart because it lists the PETSCII, ScreenCode (both character sets), BASIC character/token, and 6502 operation for every value in the 8-bit range. The numeric values are conveniently given in both decimal and hexadecimal. I'm digitizing it so I can have access to it without having the reference text open on the desk in front of me, and tagging it here as Programming Reference for others to find. Hopefully someone out there will find this chart as useful as I do.

PETSCII, ScreenCodes and BASIC codes are roughly divided into 8 blocks of 32 characters each. For this reason, the chart is presented below as eight 32-row tables. See the end discussion for an explanation of PETSCII's block structure.

SuperChart

Bit 7 Low: %0xxx xxxx

• Block 1:     000 - 031:     $00 - $1F
• Block 2:     032 - 063:     $20 - $3F
• Block 3:     064 - 095:     $40 - $5F
• Block 4:     096 - 127:     $60 - $7F
  
  

Bit 7 High: %1xxx xxxx

• Block 5:     128 - 159:     $80 - $9F
• Block 6:     160 - 191:     $A0 - $BF
• Block 7:     192 - 223:     $C0 - $DF
• Block 8:     224 - 255:     $E0 - $FF

Block 1

DEC	HEX	PETSCII	SCREEN (up/gfx, lo/up)		BASIC	6502
0	00				end-line	BRK
1	01					ORA(I,X)
2	02
3	03	stop
4	04
5	05	white				ORA Z
6	06					ASL Z
7	07
8	08	lock				PHP
9	09	unlock				ORA #
10	0A					ASL A
11	0B
12	0C
13	0D	car ret				ORA
14	0E	text				ASL
15	0F
16	10					BPL
17	11	cur down				ORA(I),Y
18	12	reverse
19	13	cur home
20	14	delete
21	15					ORA Z,X
22	16					ASL Z,X
23	17
24	18					CLC
25	19					ORA Y
26	1A
27	1B
28	1C	red
29	1D	cur right				ORA X
30	1E	green				ASL X
31	1F	blue

Corrections: Inner Space Anthology lists the block-1 alphabetic SCREEN CODES as only uppercase. They should be uppercase in the upper/graphics character set, and lowercase in the lower/upper character set, as shown above.

Corrections: Inner Space Anthology lists the SCREEN CODE $1C as a backslash. It should be the british pound symbol (£) as shown above.

Block 2

DEC	HEX	PETSCII	SCREEN (up/gfx, lo/up)		BASIC	6502
32	20	space			space	JSR
33	21	!			!	AND(I,X)
34	22	"			"
35	23	#			#
36	24	$			$	BIT Z
37	25	%			%	AND Z
38	26	&			&	ROL Z
39	27	'			'
40	28	(			(	PLP
41	29	)			)	AND #
42	2A	*			*	ROL A
43	2B	+			+
44	2C	,			,	BIT
45	2D	-			-	AND
46	2E	.			.	ROL
47	2F	/			/
48	30	0			0	BMI
49	31	1			1	AND(I),Y
50	32	2			2
51	33	3			3
52	34	4			4
53	35	5			5	AND Z,X
54	36	6			6	ROL Z,X
55	37	7			7
56	38	8			8	SEC
57	39	9			9	AND Y
58	3A	:			:
59	3B	;			;
60	3C	<			<
61	3D	=			=	AND X
62	3E	>			>	ROL X
63	3F	?			?

Block 3

DEC	HEX	PETSCII	SCREEN (up/gfx, lo/up)		BASIC	6502
64	40	@			@	RTI
65	41	a			A	EOR(I,X)
66	42	b			B
67	43	c			C
68	44	d			D
69	45	e			E	EOR Z
70	46	f			F	LSR Z
71	47	g			G
72	48	h			H	PHA
73	49	i			I	EOR #
74	4A	j			J	LSR A
75	4B	k			K
76	4C	l			L	JMP
77	4D	m			M	EOR
78	4E	n			N	LSR
79	4F	o			O
80	50	p			P	BVC
81	51	q			Q	EOR(I),Y
82	52	r			R
83	53	s			S
84	54	t			T
85	55	u			U	EOR Z,X
86	56	v			V	LSR Z,X
87	57	w			W
88	58	x			X	CLI
89	59	y			Y	EOR Y
90	5A	z			Z
91	5B	[			[
92	5C	£			£
93	5D	]			]	EOR X
94	5E	↑			↑	LSR X
95	5F	←			←

Corrections: Inner Space Anthology lists the block-3 PETSCII alphabetic characters as uppercase. They should be lowercase as shown above.

Corrections: Inner Space Anthology lists the block-3 SCREEN CODES lower/upper alphabetic characters as lowercase. They should be uppercase as shown above.

Block 4

DEC	HEX	PETSCII	SCREEN (up/gfx, lo/up)		BASIC	6502
96	60					RTS
97	61					ADC(I,X)
98	62
99	63
100	64
101	65					ADC Z
102	66					ROR Z
103	67
104	68					PLA
105	69					ADC #
106	6A					ROR A
107	6B
108	6C					JMP(I)
109	6D					ADC
110	6E					ROR
111	6F
112	70					BVS
113	71					ADC(I),Y
114	72
115	73
116	74
117	75					ADC Z,X
118	76					ROR Z,X
119	77
120	78					SEI
121	79					ADC Y
122	7A
123	7B
124	7C
125	7D					ADC X
126	7E					ROR X
127	7F

Block 5

DEC	HEX	PETSCII	SCREEN (up/gfx, lo/up)		BASIC	6502
128	80				END
129	81	orange			FOR	STA(I,X)
130	82				NEXT
131	83	load & run			DATA
132	84				INPUT#	STY Z
133	85	F1			INPUT	STA Z
134	86	F3			DIM	STX Z
135	87	F5			READ
136	88	F7			LET	DEY
137	89	F2			GOTO
138	8A	F4			RUN	TXA
139	8B	F6			IF
140	8C	F8			RESTORE	STY
141	8D	car ret			GOSUB	STA
142	8E	graphics			RETURN	STX
143	8F				REM
144	90	black			STOP	BCC
145	91	cur up			ON	STA(I),Y
146	92	rvs off			WAIT
147	93	clear			LOAD
148	94	insert			SAVE	STY Z,X
149	95	brown			VERIFY	STA Z,X
150	96	lt. red			DEF	STX Z,X
151	97	dk. grey			POKE
152	98	md. grey			PRINT#	TYA
153	99	lt. green			PRINT	STA Y
154	9A	lt. blue			CONT	TXS
155	9B	lt. grey			LIST
156	9C	purple			CLR
157	9D	cur left			CMD	STA X
158	9E	yellow			SYS
159	9F	cyan			OPEN

Corrections: Inner Space Anthology lists the block-5 reversed alphabetic SCREEN CODES as only uppercase. They should be uppercase in the upper/graphics character set, and lowercase in the lower/upper character set, as shown above.

Block 6

DEC	HEX	PETSCII	SCREEN (up/gfx, lo/up)		BASIC	6502
160	A0				CLOSE	LDY #
161	A1				GET	LDA(I,X)
162	A2				NEW	LDX #
163	A3				TAB(
164	A4				TO	LDY Z
165	A5				FN	LDA Z
166	A6				SPC(	LDX Z
167	A7				THEN
168	A8				NOT	TAY
169	A9				STEP	LDA #
170	AA				+	TAX
171	AB				-
172	AC				*	LDY
173	AD				/	LDA
174	AE				↑	LDX
175	AF				AND
176	B0				OR	BCS
177	B1				>	LDA(I),Y
178	B2				=
179	B3				<
180	B4				SGN	LDY Z,X
181	B5				INT	LDA Z,X
182	B6				ABS	LDX Z,X
183	B7				USR
184	B8				FRE	CLV
185	B9				POS	LDA Y
186	BA				SQR	TSX
187	BB				RND
188	BC				LOG	LDY X
189	BD				EXP	LDA X
190	BE				COS	LDX Y
191	BF				SIN

Note: Inner Space Anthology lists two PETSCII values at $A9 and $BA in the block-6 range. See end discussion on the changes I've made above.

Block 7

DEC	HEX	PETSCII	SCREEN (up/gfx, lo/up)		BASIC	6502
192	C0				TAN	CPY #
193	C1	A			ATN	CMP(I),X
194	C2	B			PEEK
195	C3	C			LEN
196	C4	D			STR$	CPY Z
197	C5	E			VAL	CMP Z
198	C6	F			ASC	DEC Z
199	C7	G			CHR$
200	C8	H			LEFT$	INY
201	C9	I			RIGHT$	CMP #
202	CA	J			MID$	DEX
203	CB	K			GO
204	CC	L				CPY
205	CD	M				CMP
206	CE	N				DEC
207	CF	O
208	D0	P				BNE
209	D1	Q				CMP(I),Y
210	D2	R
211	D3	S
212	D4	T
213	D5	U				CMP Z,X
214	D6	V				DEC Z,X
215	D7	W
216	D8	X				CLD
217	D9	Y				CMP Y
218	DA	Z
219	DB
220	DC
221	DD					CMP X
222	DE					DEC X
223	DF

Corrections: Inner Space Anthology lists the block-7 PETSCII alphabetic characters as lowercase. They should be uppercase as shown above.

Note: Inner Space Anthology lists two PETSCII values from $C1 to $DA, $DE and $DF in the block-7 range. See end discussion on the changes I've made above.

Block 8

DEC	HEX	PETSCII	SCREEN (up/gfx, lo/up)		BASIC	6502
224	E0					CPX #
225	E1					SBC(I),X
226	E2
227	E3
228	E4					CPX Z
229	E5					SBC Z
230	E6					INC Z
231	E7
232	E8					INX
233	E9					SBC #
234	EA					NOP
235	EB
236	EC					CPX
237	ED					SBC
238	EE					INC
239	EF
240	F0					BEQ
241	F1					SBC(I),Y
242	F2
243	F3
244	F4
245	F5					SBC Z,X
246	F6					INC Z,X
247	F7
248	F8					SED
249	F9					SBC Y
250	FA
251	FB
252	FC
253	FD					SBC X
254	FE					INC X
255	FF				π

Corrections: Inner Space Anthology lists the block-8 reversed SCREEN CODES at $F7, $F8, and $F9 as their non-reversed counterparts at $77, $78 and $79. They should be reversed as shown above.

UPDATE: February 20, 2018

Discussion

Understanding the difference between PETSCII values and Screen Codes can be confusing. The lists you will find if you search the internet for PETSCII Table do not all agree with one another, nor do they all agree with older listings found in books such as The Complete Commodore Inner Space Anthology. My SuperChart listing above is derived from Inner Space Anthology. I have made some corrections, as noted above, but I've also made some changes. I want to explain my reasons for the changes, even if others would not agree with me.

Screen Codes

Screen Codes are easy to understand when divorced from their conversion from PETSCII values. There are 256 Screen Codes. Any screen code value from 0 to 255, which occurs in a screen memory location, will be rendered by the VIC-II chip with a unique visual appearence. (When the VIC-II is in its standard text mode.)

The appearence of that character depends on the character set that is used. A character set is a 2 kilobyte bitmap. The screen code value is an index into that character set bitmap. The C64 and VIC-20 come with a character ROM, which is 4 kilobytes and contains 2 complete character sets. Additionally, custom character sets can be defined in RAM. Therefore, what actually gets displayed on screen is determined by the contents of the character set.

In the two built-in character sets, the bottom half, 0 to 127, are all unique. But the upper half, 128 to 255, are the reverse of the bottom half. Conveniently, this means that toggling bit 7 of any screen code will exchange that character with the inverse version of itself. Custom character sets do not need to adhere to this standard, but the fact that the two built-in sets work this way was a very clever design decision. In order to make the cursor blink, the KERNAL need only toggle bit 7 on and off. A nice side effect is that it allows text to be written in reverse characters for titles that stand out, and doubles the available graphics characters for drawing PETSCII-based images.

PETSCII Values

What the PETSCII values actually are is more contentious. Obviously, it cannot be the case that there is a one-to-one relationship between PETSCII values and Screen Codes. If there were, then every PETSCII value would have a visual representation, and there would be no room in the 8-bit space for control codes.

The tables above are divided into 8 blocks of 32 characters, because PETSCII itself is divided into 8 blocks. And it is easiest to understand PETSCII by comparing those blocks with each other. The 8 blocks are further subdivided into the low 4 blocks, and the high 4 blocks, as indicated in the table of contents links at the top of the SuperChart. The high 4 blocks are like a shifted version of the low 4 blocks.

• Block 1 → shifted → Block 5
• Block 2 → shifted → Block 6
• Block 3 → shifted → Block 7
• Block 4 → shifted → Block 8

PETSCII uses blocks 1, 2 and 3, and their shifted equivalents, 5, 6 and 7. PETSCII leaves block 4, and its shifted equivalent block 8, undefined. This provides a space of 192 values, however, in practice 22 of even those values are not defined.

The general scheme, with minor exceptions, is as follows:

• Block 1: Control Codes
• Block 2: Symbolic / Numeric
• Block 3: Alphabetic (Lowercase)
• Block 4: Unused

The shifted corresponding blocks are as follows:

• Block 5: Control Codes (Often with inverse role)
• Block 6: Symbolic (Graphical)
• Block 7: Alphabetic (Uppercase)
• Block 8: Unused

If you look at the two blocks of control codes, the unshifted block 1 is almost always inverted by the same code in the shifted block 5, (if that control code is dual in nature at all.) For example:

• Stop → Run
• Text → Graphics
• Cursor Down → Cursor Up
• Reverse On → Reverse Off
• Home → Clear
• Delete → Insert
• Cursor Right → Cursor Left

The alphabetic block 3 values are therefore the lowercase letters, which become their uppercase equivalents in the shifted block 7.

And the symbolic / numeric block 2 becomes a set of 32 graphical symbols in the shifted block 6. The set of symbols don't have conceptual shifted alternatives, that's why the shifted block 6 is the block used for graphic symbols.

Strings of PETSCII that are output through the KERNAL's Screen Editor are interpreted and mapped into Screen Codes, which are put in memory to be displayed. For example, there is no PETSCII code that represents "reversed lowercase a". However, the following PETSCII sequence: $0E, $12, $41, (that is "the control code for Lowercase/Uppercase character set", "the control code for Reverse On", and the PETSCII value for "a") will cause a reversed lowercase "a" to appear on the screen wherever the cursor currently is, and then the cursor will be advanced. That sequence of PETSCII is interpreted by the KERNAL, but it results in the Screen Code $81 being put into screen memory, and the Lowercase/Uppercase character set being selected.

Confusion from Character Sets and Conversions

The above description of PETSCII is hard to uncover, because of how the alternative character set is laid out, and how PETSCII values are interpreted by the KERNAL's Screen Editor and converted to Screen Codes for display.

When a Commodore 64 is first turned on it is using the Uppercase/Graphics character set, rather than the Lowercase/Uppercase character set. It may simply be that Commodore thought having more graphics characters to work with in exchange for having only one case of alphabetic characters seemed like a good trade off.

Now, if you're going to provide only one case of letters in a character set it will be uppercase not lowercase. Why is that? Well, many things are written in all-caps, but very few things are ever written in all lowercase. Hence the existence of the term all-caps, and the existence of all-caps fonts. Many words, such as the pronoun I and most proper names cannot be correctly rendered in small letters alone. In fact, in ancient writing, Latin, Greek, and Hebrew, there were no small letters, that is, no miniscules only majuscules. So it makes sense that the alternative character set is Uppercase/Graphics and not Lowercase/Graphics.

However, it also makes sense that in the Uppercase/Graphics character set, it is the lowercase PETSCII values that are replaced by uppercase glyphs. Otherwise, when in Uppercase/Graphics mode you would have to constantly hold down shift in order to get letters instead of graphic symbols. But on the other hand, when you do switch character sets, it has to be that whatever you've typed without the shift key will appear as lowercase characters, otherwise, in the Lowercase/Uppercase character set, you'd be getting uppercase characters without the shift key, and you'd have to press the shift key to get a lowercase character. That just doesn't make any sense.

And so, all this taken into consideration, one should not be confused about the PETSCII values on account of the existence, availability and even default-status of the Uppercase/Graphics character set. It is merely a character set, an alternative on-screen representation, that renders lowercase PETSCII values using a set of uppercase glyphs, and renders uppercase PETSCII values with an extended set of graphical glyphs. In a conversion from ASCII to PETSCII, though, ASCII's uppercase characters map to PETSCII's block 7, and ASCII's lowercase characters map to PETSCII's block 3.

In my opinion, a "standard code of information interchange," which is what the SCII in PETSCII stands for, cannot have multiple meanings for the same value. Given that I feel there are good arguments that the lowercase alphabetic characters are in block 3, and the uppercase equivalents are in block 7, then the Lowercase/Uppercase character set should be used for deriving the canonical PETSCII values in block 6 and 7 where there are alternatives.

Specifically, $A9 and $BA. These are mapped by the KERNAL to the Screen Codes $69 and $7A respectively. In this entire block (block 6), both character sets are identical, except for these two values. My listing indicates that the canonical PETSCII value is the character that appears in the Lowercase/Uppercase set, and that the other glyph is merely a result of swapping in an alternative character set.

The only other contentious spot is $DE and $DF in block 7. These get mapped by the KERNAL to the Screen Codes $5E and $5F, where there is an alternative appearence in the Uppercase/Graphics set. This ambiguity is not there when you type the unshifted ↑ (PETSCII $5E, mapped to Screen Code $1E), because $1E is identical in both character sets.

The Character Sets

Here are the character set images, to help clarify how the Screen Codes work and differ between them.

Lowercase/Uppercase Character Set, and Uppercase/Graphics Character Set.

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