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 a cause of the divergence between the bit-paired keyboards found in the 1960s and 1970s and the typewriter-paired keyboards that are now standard in the US. This change was made because smaller characters hit the paper with less force, and consolidating smaller characters such as '" into a pair on a single key avoided needing to adjust the force based on shift state. The standard 101/102-key PC keyboard layout was invented by Mark Tiddens of Key Tronic Corporation in 1982. IBM adopted the layout on its PC AT in 1984 (after previously using an 84-key keyboard which did not have