DIM A!            ' global 
DIM B!            ' global 
DIM C!            ' global 

C! = 100.123     '<<< This value should not change! 
B! = 123         '<<< This value should not change! 
A! = Fun!(B!, C!) '<<< C allows type translation automatically! 

PRINT "The value of A! = ", A!
PRINT "The value of B! should still be <123> ...", B!

FUNCTION Fun! (Y, Z)
  DIM A$
  DIM B!
  A$ = "Hello from inside our function!"    ' a local string variable 
  PRINT A$
  'The B! variable below is the local 
  'The C! variable is the global variable 
  'The Z variable is the function parameter Variable 
  B! = 3 * Z + C! + Y
  FUNCTION = B!
END FUNCTION

Result:

Hello from inside our function!
The value of A! =  523.123
The value of B! should still be <123> ... 123