SGN - DualBrain/bsharp Wiki
To return the sign of x.
x is any numeric expression.
If x is positive,
If x is 0,
If x is negative,
This statement is similar to, but not the same as
SIN(x), which returns a trigonometric function in radians, rather than in ones and zeros.
10 X=3 20 ON SGN(X)+2 GOTO 100, 200, 300
BASIC branches to 100 if X is negative, 200 if X is 0, and 300 if X is positive.