print "Rosetta Code - Fibonacci sequence": print
print "  n             Fn"
for x=-12 to 12 '68 max
    print using("### ", x); using("##############", FibonacciTerm(x))
next x
print
[start]
input "Enter a term#: "; n$
n$=lower$(trim$(n$))
if n$="" then print "Program complete.": end
print FibonacciTerm(val(n$))
goto [start]

function FibonacciTerm(n)
    n=int(n)
    FTa=0: FTb=1: FTc=-1
    select case
        case n=0  : FibonacciTerm=0  : exit function
        case n=1  : FibonacciTerm=1  : exit function
        case n=-1 : FibonacciTerm=-1 : exit function
        case n>1
            for x=2 to n
                FibonacciTerm=FTa+FTb
                FTa=FTb: FTb=FibonacciTerm
            next x
            exit function
        case n<-1
            for x=-2 to n step -1
                FibonacciTerm=FTa+FTc
                FTa=FTc: FTc=FibonacciTerm
            next x
            exit function
    end select
end function