LBOUND
From QB64 Wiki
The LBOUND function returns the smallest valid index (lower bound) of an array dimension.

Syntax
 result% = LBOUND(arrayName[, dimension%])
Description
 arrayName specifies the name of the array.
 dimension% specifies the dimension number, starting with
1
for the first dimension. If omitted, dimension% is assumed to be
1
.  If dimension% is less than
1
or is greater than the number of dimensions, a subscript out of range error occurs.
 If omitted, dimension% is assumed to be
 LBOUND and UBOUND are used to determine the range of valid indexes of an array.
Examples
DIM myArray(5) AS INTEGER DIM myOtherArray(1 to 2, 3 to 4) AS INTEGER PRINT LBOUND(myArray) PRINT LBOUND(myOtherArray, 2)
0 3
See also