6.7.3 Float Formats

Floating-point quantities are normally displayed in standard decimal form, with scientific notation used if the exponent is especially high or low. All significant digits are normally displayed. The commands in this section allow you to choose among several alternative display formats for floats.

The d n (calc-normal-notation) command selects the normal display format. All significant figures in a number are displayed. With a positive numeric prefix, numbers are rounded if necessary to that number of significant digits. With a negative numerix prefix, the specified number of significant digits less than the current precision is used. (Thus C-u -2 d n displays 10 digits if the current precision is 12.)

The d f (calc-fix-notation) command selects fixed-point notation. The numeric argument is the number of digits after the decimal point, zero or more. This format will relax into scientific notation if a nonzero number would otherwise have been rounded all the way to zero. Specifying a negative number of digits is the same as for a positive number, except that small nonzero numbers will be rounded to zero rather than switching to scientific notation.

The d s (calc-sci-notation) command selects scientific notation. A positive argument sets the number of significant figures displayed, of which one will be before and the rest after the decimal point. A negative argument works the same as for d n format. The default is to display all significant digits.

The d e (calc-eng-notation) command selects engineering notation. This is similar to scientific notation except that the exponent is rounded down to a multiple of three, with from one to three digits before the decimal point. An optional numeric prefix sets the number of significant digits to display, as for d s.

It is important to distinguish between the current precision and the current display format. After the commands C-u 10 p and C-u 6 d n the Calculator computes all results to ten significant figures but displays only six. (In fact, intermediate calculations are often carried to one or two more significant figures, but values placed on the stack will be rounded down to ten figures.) Numbers are never actually rounded to the display precision for storage, except by commands like C-k and C-x * y which operate on the actual displayed text in the Calculator buffer.

The d . (calc-point-char) command selects the character used as a decimal point. Normally this is a period; users in some countries may wish to change this to a comma. Note that this is only a display style; on entry, periods must always be used to denote floating-point numbers, and commas to separate elements in a list.