The UseSystem(system, opts) function sets a default system of units to be used for the current session. If a system name is specified, and such a system exists, that system will be set as the default system.

To set a default system of units for all future Maple sessions, add the UseSystem command to your Maple initialization file. For more information, see Create Maple Initialization File.

The UseUnit command is a simpler alternative to UseSystem. It selects a unit to be used for computations in the Units package. For details, see Units[UseUnit].

The opts argument can contain one or more of the following equations.

'keepOverrides'=truefalse

By default, this command overwrites the current set of units selected with the UseUnits command. To prevent this, set this option to true. For more information, see Units[UseUnit].

'strict'=truefalse

If this option is set to true, then only units that are part of the given system (including those with SI or IEC prefixes) are accepted in the Natural environment.

This prevents uncommon units (for example, ph, that is, the phot) from precluding the acceptance of system symbols (for example, ph, that is, the picohour in SI).

To enter a unit in 2-D Math input, select the unit from the appropriate Units palette. If the unit you want is not there, select $\mathrm{unit}$ and then enter the unit.

When you edit a unit, double brackets appear around it.

$\mathrm{with}\left(\mathrm{Units}\right)\:$

Automatically loading the Units[Simple] subpackage

$\mathrm{infolevel}\left[\mathrm{Units}\right]≔1$

${\mathrm{infolevel}}_{\mathrm{Units}}≔1$

$\mathrm{convert}\left(3.23\,'\mathrm{system}'\,\frac{'\mathrm{mi}'}{'h'}\right)$

convert/system:   "converting to the units m/s"

$1.443939200$

$\mathrm{UseSystem}\left('\mathrm{CGS}'\right)$

$\mathrm{convert}\left(3.23\,'\mathrm{system}'\,\frac{'\mathrm{mi}'}{'h'}\right)$

convert/system:   "converting to the units kyne"

$144.3939200$

$\mathrm{unassign}\left('\mathrm{infolevel}\left[\mathrm{Units}\right]'\right)$

$\mathrm{with}\left(\mathrm{Units}\left[\mathrm{Standard}\right]\right)\:$

$32\mathrm{Unit}\left(\frac{'\mathrm{km}'}{'h'}\right)$

$32⟦\frac{\mathrm{km}}{h}⟧$

$\mathrm{combine}\left(\,'\mathrm{units}'\right)$

$\frac{8000}{9}⟦\mathrm{kyne}⟧$

$\mathrm{with}\left(\mathrm{Units}\left[\mathrm{Natural}\right]\right)\:$

$\mathrm{UseSystem}\left('\mathrm{SI}'\,'\mathrm{strict}'\right)$

$\frac{32'\mathrm{cm}'}{'s'}$

$\frac{8}{25}⟦\frac{m}{s}⟧$

$\frac{32'\mathrm{mi}'}{'h'}$

$\frac{32\mathrm{mi}}{h}$