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
Keyboard layout piano keyboard. In countries using the Latin script, the center, alphanumeric portion of the modern keyboard is most often based on the QWERTY design by Christopher Sholes, who laid out the keys in such a way that common two-letter combinations were placed on opposite sides of the keyboard so that his mechanical keyboard would not jam, and laid out the keys in rows offset horizontally from each other by three-eighths, three-sixteenths, and three-eighths inches to provide room for the levers. Although it has been demonstrated that the QWERTY layout is not the most efficient layout for typing, it remains the