function functionname ( variable list )
statements
end function

function functionname$ ( variable list )
statements
end function

Create a function that will receive zero or more values, process those values and return either a numeric or string value. Return values are set by assigning the name of the function and executing a Return statement or allowing the End Function statement to be executed. All variables used within the function will be local to the function and will not change the values in the calling code.

In many structured languages the return value of a function is set using the Return statement. In BASIC-256 the returned value of a function is set by assigning the function name the value and either executing the Return statement or reaching the end of the function. A numeric function has the default return value of zero (0) and a string function has the default value of a zero length string (“”).

Subroutine variables may a list of zero or more, comma separated, numeric or string variables. Arrays and variables may be passed by reference using the Ref definition.

Functions should be defined at the bottom of your program, and can not be defined within another function, Subroutine or control block (If/Then, Do/Until, …)

print double$("Hello")
print triple(3)
end

function double$(a$)
   double$ = a$ + a$
end function

function triple(b)
   triple = b * 3
   return
   triple = 9999	# code never gets executed
end function

will display

HelloHello
9

0.9.9.1