calc: The Units Table
12.2 The Units Table
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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 ‘C-x * 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.
Info Catalog
calc: Basic Operations on Units
calc: Units
calc: Predefined Units