In computing FOCAL character set refers to a group of 8-bit single byte character sets introduced by Hewlett-Packard since 1979. It was used in several RPN calculators supporting the FOCAL programming language, like the HP-41C/CV/CX as well as the later HP-42S,[1][2] which was introduced in 1988[1][2] and produced up to 1995. As such, it is also used by SwissMicros' DM41/L, both introduced in 2015, and is implicitly supported by the DM42, introduced in 2017 (although the later calculator utilizes Free42, which is based on Unicode internally).

## Character set

The character set is derived from ASCII, but with the control code range and some high bit characters replaced by various special characters.

 FOCAL character set (HP-41C/CV/CX / HP 82143A)[3][4] 0 1 2 3 4 5 6 7 8 9 A B C D E F 0x ‾/♦ ∝? x̅/ā ← α β Γ ↓ Δ σ ♦ λ µ/μ ∡/∠ τ Φ 1x θ Ω &? Å å Ä ä Ö ö Ü ü Æ æ ≠ £/₤ ▒ 2x ! " # \$ % & ' ( ) * + , - . / 3x 0 1 2 3 4 5 6 7 8 9 : ; < = > ? 4x @ A B C D E F G H I J K L M N O 5x P Q R S T U V W X Y Z [ \ ] ↑/^ _ 6x `/⊤ a b c d e f g h i j k l m n o 7x p q r s t u v w x y z π | → Σ ⊦[nb 1]
Characters not in all versions

When Hewlett-Packard introduced the HP-42S in 1988, the FOCAL character set was revised to include more characters, including a number of characters already provided by the HP 82240A infrared thermo printer, which had been introduced in 1986,[5] as part of its extended variant of the 1985 revision of the HP Roman-8 character set,[6][7] although at completely different code points.

There is no code point definition for the euro sign in this character set.

 Revised FOCAL character set (HP-42S)[1] 0 1 2 3 4 5 6 7 8 9 A B C D E F 0x ÷ × √ ∫ ░ Σ ▶[nb 2] π ¿ ≤ ≥ ≠ ↵ ↓ → 1x ← µ/μ £/₤ ° Å Ñ Ä ∡/∠ ᴇ/⏨ Æ …/‥ ␛ Ö Ü ▒ ■/· 2x ! " # \$ % & ' ( ) * + , - . / 3x 0 1 2 3 4 5 6 7 8 9 : ; < = > ? 4x @ A B C D E F G H I J K L M N O 5x P Q R S T U V W X Y Z [ \ ] ↑/^ _ 6x ` a b c d e f g h i j k l m n o 7x p q r s t u v w x y z { | } ~ ⊦[nb 1] 8x ¦? ¥? ▓? ␊

Translation from HP-42S character set to the modified HP Roman-8 (supported by HP 82240A etc.) character set:

 HP translation vector 0 1 2 3 4 5 6 7 8 9 A B C D E F 0x 0x81 0x82 0x83 0x84 0x04 0x85 0x86 0x87 0x08 0x89 0x04 0x8A 0x8B 0x0D 0x0E 0x8D 1x 0x8E 0x8F 0xAF 0xB3 0xA2 0xB6 0xD8 0xA0 0x18 0xD3 0x9B 0x1B 0xDA 0xDB 0x7F 0xF2 7x 0x70 0x71 0x72 0x73 0x74 0x75 0x76 0x77 0x78 0x79 0x7A 0x7B 0x7C 0x7D 0x7E 0x94 8x 0x80 0x81 0x82 0x83 0x84 0x85 0x86 0x87 0x88 0x89 0x90 0x8B 0x8C 0x8D 0x8E 0x8F

## Notes

1. ^ a b The glyph at code point 127 () is called APPEND character in Hewlett-Packard terminology. In the HP-41C/CV/CX and HP-42S series of calculators, it is used to indicate that the following characters will be appended to the alpha register rather than replacing the existing contents of the register.
2. ^ The glyph at code point 6 is called GOOSE character in Hewlett-Packard terminology. While U+25B6 () is the preferred Unicode character for maximum cross-compatibility with established RPL character set mappings, Free42 since release 2.0.1 (2017-04-23) maps to U+25B8 () instead. [1]

## References

1. ^ a b c RPN Scientific Calculator - Owner's Manual - HP-42S (PDF) (1 ed.). Hewlett-Packard. June 1988. pp. 288–291. 00042-90001, 00042-90002. Archived (PDF) from the original on 2018-01-04. Retrieved 2018-01-04.
2. ^ a b HP-42S RPN Scientific - Programming Examples and Techniques (PDF) (1 ed.). Corvallis, OR, USA: Hewlett-Packard Company, Corvallis Division. July 1988. 00042-90020, 00042-90019. Archived (PDF) from the original on 2018-01-04. Retrieved 2018-01-04.
3. ^ Hicks, David G. (2017) [1998]. "HP-41C Synthetic Programming". The Museum of HP Calculators (MoHPC). Archived from the original on 2018-01-06. Retrieved 2018-01-06.
4. ^ Hicks, David G. (1997). "Graphic byte code table". The Museum of HP Calculators (MoHPC). Archived from the original on 2018-01-06. Retrieved 2018-01-06.
5. ^ Nelson, Richard J. (May 2010). "HP 82240B IR Printer" (PDF). HP Solve (18). Archived from the original (PDF) on 2016-09-21. Retrieved 2016-09-21.
6. ^ HP 82240A Infrared Printer (PDF) (2 ed.). Corvallis, OR, USA: Hewlett Packard, Portable Computer Division. October 1986. HP reorder number 82240-90001 (82240-90008). Archived (PDF) from the original on 2016-08-06. Retrieved 2016-08-06.
7. ^ HP 82240B Infrared Printer (1 ed.). Corvallis, OR, USA: Hewlett Packard. August 1989. pp. 17–18. HP reorder number 82240-90014. Archived from the original on 2016-08-14. Retrieved 2016-08-01.