Control-C
Control-C
Control-C is a common computer command. It is generated by pressing the C key while holding down the Ctrl key on a computer keyboard.
In graphical user interface environments that use the control key to control the active program, control-C is often used to copy highlighted text to the clipboard. In many command-line interface environments, control-C is used to abort the current task and regain user control. It is a special sequence which causes the operating system to send a signal to the active program. Usually the signal causes it to end, but the program may "catch" it and do something else, typically returning control to the user.
In graphical environments
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 Mac OS computers is Command-C.
In command-line environments
Control-C as an abort command was popularized by TOPS-20 and TOPS-10 and adopted to other systems including Unix, and Digital Equipment operating systems from which it was copied to CP/M and thus to MS-DOS and Microsoft Windows. In POSIX systems, the sequence causes the active program to receive a SIGINT signal. If the program does not specify how to handle this condition, it is terminated. Typically a program which does handle a SIGINT will still terminate itself, or at least terminate the task running inside it.
This system is usually preserved even in graphical terminal emulators. If control-C is used for copy-and-paste in the graphical environment, an ambiguity arises. Typically an alternate keystroke is assigned to one of the commands, and both appear in the emulator's menus.
As many keyboards and computer terminals once directly generated ASCII code, the choice of control-C overlapped with the ASCII end-of-text character. This character has a numerical value of three, as "C" is the third letter of the alphabet. It was chosen to cause an interrupt as it is otherwise unlikely to be part of a program's interactive interface. Many other control codes, such as control-D for the end-of-transmission character, do not generate signals and are occasionally used to control a program.
Howdy, Stranger!
It looks like you're new here. If you want to get involved, click one of these buttons!
Comments
The most common form of theta function is that occurring in the theory of elliptic functions. With respect to one of the complex variables (conventionally called z), a theta function has a property expressing its behavior with respect to the addition of a period of the associated elliptic functions, making it a quasiperiodic function. In the abstract theory this comes from a line bundle condition of descent.
Mathematics (from Greek μάθημα máthēma "knowledge, study, learning") is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity. The research required to solve mathematical problems can take years or even centuries of sustained inquiry. However, mathematical proofs are less formal and painstaking than proofs in mathematical logic. Since the pioneering work of Giuseppe Peano, David Hilbert, and others on axiomatic systems in the late 19th century, it has become customary to view mathematical research as establishing truth by rigorous deduction from appropriately chosen axioms and definitions. When those mathematical structures are good models of real phenomena, then mathematical reasoning often provides insight or predictions.