GNU Emacs Calc 2.02 Manual

12.2: The Units Table

The u v (calc-enter-units-table) command displays the units table in another buffer called *Units Table*. Each entry in this table gives the unit name as it would appear in an expression, the definition of the unit in terms of simpler units, and a full name or description of the unit. Fundamental units are defined as themselves; these are the units produced by the u b command. The fundamental units are meters, seconds, grams, kelvins, amperes, candelas, moles, radians, and steradians.

The Units Table buffer also displays the Unit Prefix Table. Note that two prefixes, ``kilo'' and ``hecto,'' accept either upper- or lower-case prefix letters. `Meg' is also accepted as a synonym for the `M' prefix. Whenever a unit name can be interpreted as either a built-in name or a prefix followed by another built-in name, the former interpretation wins. For example, `2 pt' means two pints, not two pico-tons.

The Units Table buffer, once created, is not rebuilt unless you define new units. To force the buffer to be rebuilt, give any numeric prefix argument to u v.

The u V (calc-view-units-table) command is like u v except that the cursor is not moved into the Units Table buffer. You can type u V again to remove the Units Table from the display. To return from the Units Table buffer after a u v, type M-# c again or use the regular Emacs C-x o (other-window) command. You can also kill the buffer with C-x k if you wish; the actual units table is safely stored inside the Calculator.

The u g (calc-get-unit-definition) command retrieves a unit's defining expression and pushes it onto the Calculator stack. For example, u g in will produce the expression `2.54 cm'. This is the same definition for the unit that would appear in the Units Table buffer. Note that this command works only for actual unit names; u g km will report that no such unit exists, for example, because km is really the unit m with a k (``kilo'') prefix. To see a definition of a unit in terms of base units, it is easier to push the unit name on the stack and then reduce it to base units with u b.

The u e (calc-explain-units) command displays an English description of the units of the expression on the stack. For example, for the expression `62 km^2 g / s^2 mol K', the description is ``Square-Kilometer Gram per (Second-squared Mole Degree-Kelvin).'' This command uses the English descriptions that appear in the righthand column of the Units Table.