Control-C else, typically returning control to the user. Ctrl-C was one of a handful of keyboard sequences chosen by the program designers at Xerox PARC to control text editing, with Ctrl-Z (Undo), Ctrl-X (Cut), Ctrl-V (Paste), and Ctrl-P (Print). The first four letters are all located together at the left end of the bottom row of the standard QWERTY keyboard, and P towards the upper right. The equivalent key combination on Macintosh computers is Command-C. Control-C as an abort command was popularized by TOPS-20 and TOPS-10 and adopted by other systems including Unix. It was also adopted by Digital Equipment operating
Dvorak Simplified Keyboard took 100 hours of training, more than was claimed in Dvorak's Navy test), Strong took a second group of QWERTY typists chosen for equal ability to the Dvorak group and retrained them in QWERTY in order to improve their speed at the same time the Dvorak typists were training. The carefully controlled study failed to show any benefit to the Dvorak keyboard layout in typing or training speed. Strong recommended speed training with QWERTY rather than switching keyboards, and attributed the previous apparent benefits of Dvorak to improper experimental design and outright bias on the part of Dvorak, who had