PETSCII

PETSCII (PET Standard Code of Information Interchange), also known as CBM ASCII, is the character set used in Commodore Business Machines (CBM)'s 8-bit home computers, starting with the PET from 1977 and including the C16, C64, C116, C128, CBM-II, Plus/4, and VIC-20.

PETSCII

PETSCII (shifted and unshifted)
Language(s)	English with pseudographics
Classification	8-bit extended early ASCII
Based on	US-ASCII (1963 version)

History

The character set was largely designed by Leonard Tramiel (the son of Commodore CEO Jack Tramiel) and PET designer Chuck Peddle. The graphic characters of PETSCII were one of the extensions Commodore specified for Commodore BASIC when laying out desired changes to Microsoft's existing 6502 BASIC to Microsoft's Ric Weiland in 1977.[1] The VIC-20 used the same pixel-for-pixel font as the PET, although the characters appeared wider due to the VIC's 22-column screen. The Commodore 64, however, used a slightly re-designed, heavy upper-case font, essentially a thicker version of the PET's, in order to avoid color artifacts created by the machine's higher resolution screen. The C64's lowercase characters are identical to the lowercase characters in the Atari 800's system font (released several years earlier).

Peddle claims the inclusion of card suit symbols was spurred by the demand that it should be easy to write card games on the PET (as part of the specification list he received).

Specifications

C64 startup screen with shifted and unshifted modes of PETSCII, and the two characters from ASCII-1963

PETSCII Chart as displayed on the C64 in shifted and unshifted modes. (Not shown are control codes, as well as characters in the $C0–$FF range, which are the standard uppercase keycodes returned from the keyboard, and which are mirrored to the range $60–$7F.)

PETSCII is based on the 1963 version of ASCII (rather than the 1967 version, which most if not all other computer character sets based on ASCII use). Assuming the graphics mode is unshifted, PETSCII has only uppercase letters in its powerup state, an up-arrow ( ↑ ) instead of a caret ( ^ ) in position $5E and a left-arrow ( ← ) instead of an underscore ( _ ) in position $5F, these two variants are common in ASCII-1963.[2] Also, in the VIC-20 and C64 version, the backslash ( \ ) in position $5C is occupied by a British pound sign ( £ ) (preceding the usage of the same ASCII code by the Japanese and Korean versions of ISO 646 for their respective currency symbols). In unshifted mode, codes $60–$7F and $A0–$FF are allotted to CBM-specific block graphics characters (horizontal and vertical lines, hatches, shades, triangles, circles and card suits). Ranges $00–$1F and $80–$9F have control codes.

The Commodore PET's lack of a programmable bitmap-mode for computer graphics, as well as it having no redefinable character set capability, may be one of the reasons PETSCII was developed; by creatively using the well thought-out block graphics, a higher degree of sophistication in screen graphics is attainable than by using plain ASCII's letter/digit/punctuation characters. In addition to the relatively diverse set of geometrical shapes that can thus be produced, PETSCII allows for several grayscale levels by its provision of differently hatched checkerboard squares/half-squares. Finally, the reverse-video mode (see below) is used to complete the range of graphics characters, in that it provides mirrored half-square blocks.

PETSCII also has a text mode, in which lowercase letters occupy the range $41–$5A, and uppercase letters occupy the range $C1–$DA. The mode is toggled by holding one of the SHIFT keys and then pressing and releasing the Commodore key. Regardless of whether the chip has undergone this graphic "shift", there are block graphic characters in the range of $E0-FF. This serves to distinguish PETSCII from those kinds of ASCII that go back no farther than ASCII-1967, so any text transfer between an 8-bit Commodore machine and one that uses 1967-derived ASCII would result in text where uppercase letters appear to be lowercase, and lowercase letters uppercase. There is no easy Boolean operation to change these cases to the proper case. Thus, as with other computers based on non-standard-ASCII character sets, software conversion is needed when exchanging text files and/or telecommunicating with standard ASCII systems. The other ranges are unchanged in shifted mode; this means that the other characters added in ASCII-1967 besides lowercase letters – i.e. the grave accent, curly braces, vertical bar, and tilde – do not exist in PETSCII.

Included in PETSCII are cursor and screen control codes, such as {HOME}, {CLR}, {RVS ON}, and {RVS OFF} (the latter two activating/deactivating reverse-video character display). The control codes appeared in program listings as reverse-video graphic characters, although some computer magazines, in their efforts to provide more clearly readable listings, pretty-printed the codes using their actual names, like the above examples. Such names were commonly enclosed in curly braces in the listings. This prevented ambiguity, since, as mentioned, PETSCII had no curly brace characters. The screen control codes were essentially similar to escape codes for text based computer terminals.

As indicated above, PETSCII provides for shifting between the power-on default (unshifted) uppercase+graphics character set and the alternative (shifted) lower+uppercase set (where the shifted set contains a subset of the block graphic characters of the unshifted set). The shift between modes is done by POKEing location 59468 with the value 14 to select the alternative set or 12 to revert to standard. On C64 the sets are alternated by flipping bit 2 of the byte 53272. On some models of PET this can also be achieved via special control code PRINT CHR$(14) which adjust the line spacing as well as changing the character set; the POKE method is still available and does not alter the line spacing.[3] Thus, screen editor state changes, rather than the employment of separate ASCII codes, are used to choose between single-case (all capitals) and dual case. In the VIC-20, C64, and later machines (not including the CBM business computers), color codes supplement the other screen control codes. (The colors of the VIC-20 and C64/128 are listed in the VIC-II article.)

Character set

Not all of the characters encoded by PETSCII are 'graphic' and not all of them have a corresponding Unicode representation. The following table shows for PETSCII characters the corresponding Unicode character and code point. Control characters and other non-printing characters are represented by their names. Where a particular code point encodes both a shifted and unshifted character, both characters are shown, with the unshifted character on the left and the shifted character on the right. Row and column headings indicate the hexadecimal digit combinations to produce the eight-bit code value; e.g., the letter L is at code value $4C.

Note that the table below is for the Commodore 64, Commodore 16, and Commodore 128. Control characters differ between these machines and are presented in separate tables. Other Commodore machines used slightly different versions of PETSCII, which used different control characters and in some cases different graphic characters. For example, on CBM machines prior to the VIC-20, characters $2C and $6C both produced a comma character, albeit with slightly different semantics.[4]

The actual character generator ROM used a different set of assignments. For example, to display the characters "@ABC" on screen by directly writing into the screen memory, one would POKE the decimal values 0, 1, 2, and 3 rather than 64, 65, 66, and 67.[5]

PETSCII (Commodore 64, 16, and 128)[6][7][8][9]

	_0	_1	_2	_3	_4	_5	_6	_7	_8	_9	_A	_B	_C	_D	_E	_F
0_ 0
1_ 16
2_ 32	SP 0020	! 0021	" 0022	# 0023	$ 0024	% 0025	& 0026	' 0027	( 0028	) 0029	* 002A	+ 002B	, 002C	- 002D	. 002E	/ 002F
3_ 48	0 0030	1 0031	2 0032	3 0033	4 0034	5 0035	6 0036	7 0037	8 0038	9 0039	: 003A	; 003B	< 003C	= 003D	> 003E	? 003F
4_ 64	@ 0040	A a 0041 0061	B b 0042 0062	C c 0043 0063	D d 0044 0064	E e 0045 0065	F f 0046 0066	G g 0047 0067	H h 0048 0068	I i 0049 0069	J j 004A 006A	K k 004B 006B	L l 004C 006C	M m 004D 006D	N n 004E 006E	O o 004F 006F
5_ 80	P p 0050 0070	Q q 0051 0071	R r 0052 0072	S s 0053 0073	T t 0054 0074	U u 0055 0075	V v 0056 0076	W w 0057 0077	X x 0058 0078	Y y 0059 0079	Z z 005A 007A	[ 005B	£ 00A3	] 005D	↑ 2191	← 2190
6_ 96	🭹 1FB79	♠ A 2660 0041	🭲 B 1FB72 0042	🭸 C 1FB78 0043	🭷 D 1FB77 0044	🭶 E 1FB76 0045	🭺 F 1FB7A 0046	🭱 G 1FB71 0047	🭴 H 1FB74 0048	╮ I 256E 0049	╰ J 2570 004A	╯ K 256F 004B	🭼 L 1FB7C 004C	╲ M 2572 004D	╱ N 2571 004E	🭽 O 1FB7D 004F
7_ 112	🭾 P 1FB7E 0050	● Q 25CF 0051	🭻 R 1FB7B 0052	♥ S 2665 0053	🭰 T 1FB70 0054	╭ U 256D 0055	╳ V 2573 0056	○ W 25CB 0057	♣ X 2663 0058	🭵 Y 1FB75 0059	♦ Z 2666 005A	┼ 253C	🮌 1FB8C	│ 2502	π 🮖 03C0 1FB96	◥ 🮘 25E5 1FB98
8_ 128
9_ 144
A_ 160	NBSP 00A0	▌ 258C	▄ 2584	▔ 2594	▁ 2581	▏ 258F	▒ 2592	▕ 2595	🮏 1FB8F	◤ 🮙 25E4 1FB99	🮇 1FB87	├ 251C	▗ 2597	└ 2514	┐ 2510	▂ 2582
B_ 176	┌ 250C	┴ 2534	┬ 252C	┤ 2524	▎ 258E	▍ 258D	🮈 1FB88	🮂 1FB82	🮃 1FB83	▃ 2583	🭿 ✓ 1FB7F 2713	▖ 2596	▝ 259D	┘ 2518	▘ 2598	▚ 259A
C_ 192	🭹 1FB79	♠ A 2660 0041	🭲 B 1FB72 0042	🭸 C 1FB78 0043	🭷 D 1FB77 0044	🭶 E 1FB76 0045	🭺 F 1FB7A 0046	🭱 G 1FB71 0047	🭴 H 1FB74 0048	╮ I 256E 0049	╰ J 2570 004A	╯ K 256F 004B	🭼 L 1FB7C 004C	╲ M 2572 004D	╱ N 2571 004E	🭽 O 1FB7D 004F
D_ 208	🭾 P 1FB7E 0050	● Q 25CF 0051	🭻 R 1FB7B 0052	♥ S 2665 0053	🭰 T 1FB70 0054	╭ U 256D 0055	╳ V 2573 0056	○ W 25CB 0057	♣ X 2663 0058	🭵 Y 1FB75 0059	♦ Z 2666 005A	┼ 253C	🮌 1FB8C	│ 2502	π 🮖 03C0 1FB96	◥ 🮘 25E5 1FB98
E_ 224	NBSP 00A0	▌ 258C	▄ 2584	▔ 2594	▁ 2581	▏ 258F	▒ 2592	▕ 2595	🮏 1FB8F	◤ 🮙 25E4 1FB99	🮇 1FB87	├ 251C	▗ 2597	└ 2514	┐ 2510	▂ 2582
F_ 240	┌ 250C	┴ 2534	┬ 252C	┤ 2524	▎ 258E	▍ 258D	🮈 1FB88	🮂 1FB82	🮃 1FB83	▃ 2583	🭿 ✓ 1FB7F 2713	▖ 2596	▝ 259D	┘ 2518	▘ 2598	π 🮖 03C0 1FB96

  Letter   Number   Punctuation   Symbol   Other   Undefined

Control characters

Some PETSCII codes cannot be printed and are only used for keyboard input (e.g. F1, RUN/STOP).

PET 2001 keyboard layout, illustrating PETSCII graphics characters

Commodore 64 control characters

PETSCII control characters (Commodore 64)[6]

	_0	_1	_2	_3	_4	_5	_6	_7	_8	_9	_A	_B	_C	_D	_E	_F
0_ 0				STOP		WHITE			SHIFT DISABLE	SHIFT ENABLE				RETURN	TEXT MODE 000E
1_ 16		CURSOR DOWN 0084	REVERSE ON	HOME	DEL 0008								RED	CURSOR RIGHT	GREEN	BLUE
8_ 128		ORANGE		RUN		F1	F3	F5	F7	F2	F4	F6	F8	LF 000A	GRAPHICS 000F
9_ 144	BLACK	CURSOR UP 008D	REVERSE OFF	CLR	INSERT	BROWN	PINK	DARK GRAY	MEDIUM GRAY	LIGHT GREEN	LIGHT BLUE	LIGHT GRAY	PURPLE	CURSOR LEFT	YELLOW	CYAN

Commodore 16 control characters

PETSCII control characters (Commodore 16)[6]

	_0	_1	_2	_3	_4	_5	_6	_7	_8	_9	_A	_B	_C	_D	_E	_F
0_ 0				STOP		WHITE			SHIFT DISABLE	SHIFT ENABLE				RETURN	TEXT MODE 000E
1_ 16		CURSOR DOWN 0084	REVERSE ON	HOME	DEL 0008							ESC 001B	RED	CURSOR RIGHT	GREEN	BLUE
8_ 128		ORANGE	FLASHING ON	RUN	FLASHING OFF	F1	F3	F5	F7	F2	F4	F6	HELP	LF 000A	GRAPHICS 000F
9_ 144	BLACK	CURSOR UP 008D	REVERSE OFF	CLR	INSERT	BROWN	YELLOW GREEN	PINK	BLUE GREEN	LIGHT BLUE	DARK BLUE	LIGHT GREEN	PURPLE	CURSOR LEFT	YELLOW	CYAN

Commodore 128, 40-column mode control characters

PETSCII control characters (Commodore 128, 40-column mode)[6]

	_0	_1	_2	_3	_4	_5	_6	_7	_8	_9	_A	_B	_C	_D	_E	_F
0_ 0				STOP		WHITE		BELL 0007		HT 0009	LF 000A	SHIFT ENABLE	SHIFT DISABLE	RETURN	TEXT MODE 000E
1_ 16		CURSOR DOWN 0084	REVERSE ON	HOME	DEL 0008				TAB SET/ CLEAR 0088			ESC 001B	RED	CURSOR RIGHT	GREEN	BLUE
8_ 128		ORANGE		RUN		F1	F3	F5	F7	F2	F4	F6	F8	LF 000A	GRAPHICS 000F
9_ 144	BLACK	CURSOR UP 008D	REVERSE OFF	CLR	INSERT	BROWN	PINK	DARK GRAY	MEDIUM GRAY	LIGHT GREEN	LIGHT BLUE	LIGHT GRAY	PURPLE	CURSOR LEFT	YELLOW	CYAN

Commodore 128, 80-column mode control characters

PETSCII control characters (Commodore 128, 80-column mode)[6]

	_0	_1	_2	_3	_4	_5	_6	_7	_8	_9	_A	_B	_C	_D	_E	_F
0_ 0			UNDERLINE ON	STOP		WHITE		BELL 0007		HT 0009	LF 000A	SHIFT ENABLE	SHIFT DISABLE	RETURN	TEXT MODE 000E	FLASHING ON
1_ 16		CURSOR DOWN	REVERSE ON	HOME	DEL 0008				TAB SET/ CLEAR 0088			ESC 001B	RED	CURSOR RIGHT	GREEN	BLUE
8_ 128		DARK PURPLE	UNDERLINE OFF	RUN		F1	F3	F5	F7	F2	F4	F6	F8	LF 000A	GRAPHICS 000F	FLASHING OFF
9_ 144	BLACK	CURSOR UP 008D	REVERSE OFF	CLR	INSERT	DARK YELLOW	PINK	DARK CYAN	MEDIUM GRAY	LIGHT GREEN	LIGHT BLUE	LIGHT GRAY	PURPLE	CURSOR LEFT	YELLOW	CYAN

Commodore 65 prototype, 80-column mode control characters

PETSCII control characters (Commodore 65 prototype, 80-column mode)[10]

	_0	_1	_2	_3	_4	_5	_6	_7	_8	_9	_A	_B	_C	_D	_E	_F
0_ 0			UNDERLINE ON	STOP		WHITE		BELL 0007		HT 0009	LF 000A	SHIFT ENABLE	SHIFT DISABLE	RETURN	TEXT MODE 000E	FLASHING ON
1_ 16	F9	CURSOR DOWN	REVERSE ON	HOME	DEL 0008	F10	F11	F12	TAB SET/ CLEAR 0088	F13	F14	ESC 001B	RED	CURSOR RIGHT	GREEN	BLUE
8_ 128		ORANGE	UNDERLINE OFF	RUN	HELP	F1	F3	F5	F7	F2	F4	F6	F8	LF 000A	GRAPHICS 000F	FLASHING OFF
9_ 144	BLACK	CURSOR UP 008D	REVERSE OFF	CLR	INSERT	BROWN	LIGHT RED	LIGHT GRAY	MEDIUM GRAY	LIGHT GREEN	LIGHT BLUE	DARK GRAY	PURPLE	CURSOR LEFT	YELLOW	CYAN

Base 128

Out of PETSCII's first 192 codes, 164 have visible representations (for the control codes, these are visible when quoted): 5 (white), 17–20 and 28–31 (colors and cursor controls), 32–90 (ASCII equivalent), 91–127 (graphics), 129 (orange), 133–140 (function keys), 144–159 (colors and cursor controls), and 160–192 (graphics). This theoretically permits encodings, such as base128, in DATA statements, or perhaps between PETSCII-speaking machines; for example, 33–127, 160–192.

See also

• ATASCII
• Atari ST character set
• ZX Spectrum character set
• Extended ASCII
• Text semigraphics

Notes

1. ^ The Amiga home/personal computer family uses standard ISO-8859-1.
2. ^ see On The Edge by Brian Bagnall, ISBN 0-9738649-0-7, pp. 43, 54–55.

References

1. A Conversation with Chuck Peddle, Bil Herd, Jeri Ellsworth - part 3 (2009 videoconference, 06:30) Archived 9 January 2011 at the Wayback Machine
2. Jennings, Thomas Daniel (20 April 2016) [1999]. "An annotated history of some character codes or ASCII: American Standard Code for Information Infiltration". World Power Systems (WPS). Archived from the original on 22 May 2016.
3. THE COMMODORE PET COMPUTER / FREQUENTLY ASKED QUESTIONS FILE - VERSION 1.7 ( Updated 25 November 2000) BY LARRY ANDERSSON, COMMODORE COLLECTOR AND PET ENTHUSIAST
4. Commodore Trivia Edition #26 Answers for February 1996
5. "C64VPRI.TXT", L2/19-025: Proposal to add characters from legacy computers and teletext to the UCS (PDF), 4 January 2019
6. Oy, Aivosto (2014), Commodore PETSCII character sets (PDF)
7. "ReadMe.txt", L2/19-025: Proposal to add characters from legacy computers and teletext to the UCS (PDF), 4 January 2019
8. "C64IPRI.TXT", L2/19-025: Proposal to add characters from legacy computers and teletext to the UCS (PDF), 4 January 2019
9. "C64IALT.TXT", L2/19-025: Proposal to add characters from legacy computers and teletext to the UCS (PDF), 4 January 2019
10. C64DX System Specification

External links

• PETSCII character map, part 1, part 2, part 3 (JPEG)
• An attempt at PETSCII to Unicode mapping, unshifted, shifted
• Another PETSCII to Unicode mapping and a TrueType font using that mapping
• Commodore 128 PETSCII control characters
• Typography in 8 bits: System fonts
• Online PETSCII-art editor
• PETSCII-art