indexbase
ACTION: define the index base for an array
USE: most software assumes an indexbase of 0 or 1
EXAMPLE:
indexbase 0

REMARKS: the default indexbase is 1 but C code normally assumes 0.
If the indexbase is defined inside a scope, such as a function then it
only applies within the scope and reverts to its previous value outside the scope.

RELATED: dim #case #semicolon