The ▶ operator converts an expression to a different unit. Usually, this refers to the built-in units (such as _m (meters), _mph (miles per hour, etc.) which you can select from the UNITS menu.
To use it, you must first have the expression on the left in terms of some unit — this is done by multiplying it by that unit. For instance, "5 meters" is written as 5_m or 5*_m (where _m is the unit). You can combine units as well: for instance, 5_m^2 (5 square meters) or 30_km/_hr (30 kilometers per hour).
To convert that into a different unit, type ▶ and then a different unit to convert to (again, you can combine units). For instance, to convert 5 square meters to acres, type 5_m^2▶_acre. (Note: the result will always be expressed as a decimal)
:30_km/_hr▶_m/_s 8.33333*_m/_s :5_N▶_dyne 500000.*_dyne
You can't use ▶ to convert between units of temperature (degrees Celsius to degrees Fahrenheit, for instance), since the calculator isn't sure if you mean absolute temperature or a change in temperature instead. Use the tmpCnv() and ΔtmpCnv() commands instead.
It's possible to define your own units as well: units are just any variable beginning with an underscore, and ▶ will perform just as well converting between those. There are two ways to go about it. The first is to define your units in terms of existing ones: for instance, you might define a furlong (one-eighth of a mile) as follows:
:1/8_mi→_furlong 1/8*_mi :110_yd▶_furlong .5*_furlong
The second method is to start with a unit or several units to keep undefined (for instance, _x). You can then define other units in terms of _x, and convert between them:
:5_x→_y 5*_x :3_y▶_x 15.*_x :10_x/_s▶_y/_s 2.*_y/_s
Units are treated just like variables, except that they're universal across folders: you can have only one instance of _x, and you can access it as _x no matter which folder you're in. You can use this if you want to define a universal variable to access in any folder: for instance, if you define a program as _prgm(), you can run it with _prgm() from any folder.
345 - Inconsistent units happens when converting between two units that measure different types of quantities (for instance, converting length to time).