Pressing a digit or other numeric key begins numeric entry using the minibuffer. The number is pushed on the stack when you press the RET or SPC keys. If you press any other non-numeric key, the number is pushed onto the stack and the appropriate operation is performed. If you press a numeric key which is not valid, the key is ignored.
There are three different concepts corresponding to the word “minus,” typified by ‘a-b’ (subtraction), ‘-x’ (change-sign), and ‘-5’ (negative number). Calc uses three different keys for these operations, respectively: -, n, and _ (the underscore). The - key subtracts the two numbers on the top of the stack. The n key changes the sign of the number on the top of the stack or the number currently being entered. The _ key begins entry of a negative number or changes the sign of the number currently being entered. The following sequences all enter the number -5 onto the stack: 0 RET 5 -, 5 n RET, 5 RET n, _ 5 RET, 5 _ RET.
Some other keys are active during numeric entry, such as # for non-decimal numbers, : for fractions, and @ for HMS forms. These notations are described later in this manual with the corresponding data types. See Data Types.
During numeric entry, the only editing key available is DEL.