Character Sets (changes)

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Character Sets

Introduction

This chapter aims to document all the alphabet sets available under RISC OS. International Standards Organisation ISO 8859 document forms the basis of most sets.

Loading alphabets

Loading an alphabet overlays the previous alphabet. Most alphabets have a some undefined characters, indicated below in light grey. In these cases, the previous character definition for that code is unchanged.

Character codes 0 – 31 and 127 are not printable characters but have special meanings described in VDU Codes. They are indicated below by a dark grey square.

Alphabets can be loaded using OS_Byte 71 or *Alphabet.

How alphabets are initially set up

The default alphabet

Booting of the kernel sets up a default alphabet.

This default alphabet always contains all character definitions from the Latin1 alphabet. N.B. This definition has been gradually extended by adding extra characters in the range &80 – &9F (128 – 159).

In the case of characters neither defined in the Latin1 alphabet nor used by the VDU drivers, the kernel’s representation varies. RISC OS 2 represents them by the underlined string ‘These•characters•are•not•defined’. RISC OS 3 displays the character code’s hexadecimal value. Some of these undefined characters may be used in the future to further extend the Latin1 alphabet, or their representation may change. Users are most likely to redefine these characters if necessary. Consequently, their initial representation must not be relied upon.

The configured alphabet

The default alphabet is then overlaid according to the computer’s configured territory. This configuration is set by *Configure Territory. Under RISC OS 2, the overlay depends on the computer’s configured country; see *Configure Country.

The window manager

Some characters are redefined when The Window Manager starts. RISC OS 2 used these to draw windows’ borders, and so have to be present for correct rendering of the desktop. Some of these definitions are retained in later versions of RISC OS for backwards compatibility, but are otherwise unused. The presence of these characters must not be relied upon unless your program is running under the desktop in RISC OS 2.

Keyboard shortcuts

The *Country command explains the relationship between country, alphabet and keyboard. Some useful keyboard shortcuts exist which can be used to access various characters and alphabets. These can be used wherever you can use the keyboard: e.g. at the Command Line, in a text editor, or when entering a filename to save a file. The first two keystroke combinations allow easy switching between keyboard layouts:

Where <x> denotes a decimal character code typed on the numeric keypad

The keyboard layout is switched by the following sequence:

1. Press and hold Alt and Ctrl together
2. Press F12
3. Release Ctrl
4. Still holding Alt, type on the numeric keypad the international telephone dialling code for the country you want (e.g. 49 for Germany, 39 for Italy, 33 for France)
5. Release Alt

Character set tables

(Character set tables still to be corrected/completed.)

• Latin1 alphabet (ISO 8859/1 + Acorn extensions)

Latin1 alphabet (ISO 8859/1 + Acorn extensions)

• RISC OS 2: characters &80 – &9F (128 – 159) undefined.
• RISC OS 3: characters &80 – &8B (128 – 139) undefined.

Characters 128-159 are not part of the ISO Latin 1 character set, and were partially populated by Acorn. The dark grey characters in the above table may be defined by the Wimp when plotting text in System Font.

• Note: characters 128-159 (aka x80 to x9F) aren’t part of the Latin 1 character set – refer also to Unicode in RISC OS at riscos.info.