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A Boolean flag is cell-sized. A cell with all bits clear represents the
flag false and a flag with all bits set represents the flag
true. Words that check a flag (for example, IF) will treat
a cell that has any bit set as true.
True ( unknown ) unknown “True”
False ( unknown ) unknown “False”
on ( a-addr – ) gforth-1.0 “on”
Set the (value of the) variable at a-addr to true.
off ( a-addr – ) gforth-1.0 “off”
Set the (value of the) variable at a-addr to false.
select ( u1 u2 f – u ) gforth-1.0 “select”
If f is false, u is u2, otherwise u1.