Group switching
The group switching is used to effect on input keyboards for computers and word processing devices that a simultaneous or subsequent actuation of a key causes the input of a character from the "secondary group". This affects keyboard layouts in which not all characters can only be entered directly, with the help of the shift key or with the help of the third-level selection key ( Alt-Gr key).
The international standard ISO / IEC 9995-2 : 2009 recommends a dedicated "group switchover key" ⇨marked with the symbol to the right of the third-level selection key ( Alt Grkey). In contrast to the shift key, this key is not pressed simultaneously with the key for the character to be entered, but, like a dead key , is pressed and released before the selected character key is pressed.
If this key is not available, this standard provides for the key combination Alt Gr+ ⇧(shift key). Again, this key combination must be released before the selected character key is pressed. This enables the character from the secondary group to be selected using the shift key or the third-level selection key (Alt Gr).
According to the international standard ISO / IEC 9995-1: 2009, in keyboard layouts with a secondary group, the characters of the primary group must always be displayed on the left edge of the key area, and the characters of the secondary group on the right edge. In the case of keyboard layouts without a secondary group (such as the German keyboard layout T1 ), however, the characters of the third level of the primary group (ie the characters entered with Alt Gr) are displayed on the bottom right of the key surfaces. In this case (especially when rewriting a German T1 keyboard to an E1 keyboard ) the characters of the secondary group must be added in the upper right corner of the key surfaces. As long as (as with the E1 keyboard) the lowercase letters can also symbolize the associated uppercase letters (to be entered with the shift key), this is not in accordance with the ISO standard mentioned, but practicable (and because of the larger possible individual characters it also has ergonomic advantages ). This is why the current German keyboard standard DIN 2137-01: 2018-12 expressly standardizes this arrangement.
"Extra dial button" on the German standard keyboard
Since group switching with the key combination recommended in ISO / IEC 9995-2 is not compatible with the keyboard drivers in Microsoft Windows (as of December 2018), the current German keyboard standard DIN 2137-01: 2018-12 defines the key combination Alt Gr+ fas group switching . The “F” key was chosen for ergonomic reasons: for ten-finger touch typists it is in the most favorable position of the left index finger in the back row and at the same time allows the capital ẞ to be positioned on the g key (“g for large”) and leave the sub-letter dead keys to the right of it in a sequence.
The combination mentioned is referred to as the “ extra selection key ”, the group of characters that can be entered with it as “extra group” and the characters in this group as “extra characters”. It is also stipulated that some of these extra characters, which are only important for special user groups, are not written on the key tops in order not to overload the appearance of the keyboard for the general public.
A special symbol has also been standardized for the extra selection key, which must be shown on the Alt Grkey to be pressed with. The lettering "Ex" is the abbreviation for "Extra". The direction of the arrow indicates that the characters shown in the upper right corner of the key tops are addressed. , The thicker arrow base points out that the operation is other than the symbolized by a likewise shown with outline arrow Umschalttastenfunktion (namely, operation in advance rather than simultaneously). It is also recommended that both the extra characters themselves and the extra selection key symbol be displayed in a different color or shade of gray than the other characters.
So z. B. entered:
- Icelandic þ (lowercase): Alt Gr+ f, after t.
- Icelandic Þ (capital letter): Alt Gr+ f, followed by ⇧ Umschalttaste+ T.
- Long s ("ſ"): Alt Gr+ f, afterwards s.
Individual evidence
- ↑ DIN 2137-2: 2018-12, Appendix D "Explanations for the keyboard layout E1", Section D.3.4
- ↑ DIN 2137-01: 2018-12, Section 5.2 "Assignment with characters"
- ↑ a b DIN 2137-01: 2018-12, Appendix D "Explanations of the keyboard layout E1", Section D.2 "Character arrangement: general"
- ↑ DIN 2137-01: 2018-12, Appendix B "Symbols"