Dvorak Simplified Keyboard closed out. Apple also includes a Dvorak variant they call "Dvorak – Qwerty ⌘". With this layout, the keyboard temporarily becomes QWERTY when the Command (⌘/Apple) key is held down. By keeping familiar keyboard shortcuts like "close" or "copy" on the same keys as ordinary QWERTY, this lets some people use their well-practiced muscle memory and may make the transition easier. Mac OS and subsequently Mac OS X allow additional "on-the-fly" switching between layouts: a menu-bar icon (by default, a national flag that matches the current language, a 'DV' represents Dvorak and a 'DQ' represents Dvorak – Qwerty ⌘) brings
QWERTY Edison's 1872 electric print-wheel device which later became the basis for Teletype machines; Lucien Stephen Crandall's typewriter (the second to come onto the American market) whose type was arranged on a cylindrical sleeve; the Hammond typewriter of 1887 which used a semi-circular "type-shuttle" of hardened rubber (later light metal); and the Blickensderfer typewriter of 1893 which used a type wheel. The early Blickensderfer's "Ideal" keyboard was also non-QWERTY, instead having the sequence "DHIATENSOR" in the home row, these 10 letters being capable of composing 70% of the words in the English language. Alternating hands while typing is a desirable trait