On a calculator, “AC” denotes the “All Clear” function. Depressing this key completely erases the current calculation displayed, resetting the calculator to its initial state, typically zero. For example, if one enters “2 + 2 =” and then presses the “AC” button, the display will revert to zero, clearing the prior input and result.
This function is essential for correcting errors, starting fresh calculations, and preventing the accumulation of unintended operations. Its presence ensures users can easily recover from mistakes without needing to manually undo each step. Historically, this full reset capability has been a standard feature on virtually all electronic calculators, providing a fundamental level of user control.