===== Subroutine =====

==== Format ====
**subroutine** subroutinename ( //variable list// )\\
//statements//\\
**end subroutine**

**subroutine** subroutinename$ ( //variable list// )\\
//statements//\\
**end subroutine**

==== Description ====
Create a subroutine (or subprogram) that will receive zero or more values and process those values.  A subroutine does not return a value back to the user, it just does what you want it to do.  Execution of a subroutine will terminate and control will be returned to the "[[call|call]]ing" program when a [[Return|Return]] statement is executed or by allowing the //End Subroutine// statement to be reached.  All variables used within the subroutine, that have not been previously declared as [[global|Global]], will be local to the subroutine and will not change the values in the calling code.

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|Ref]] definition.

Subroutines should be defined at the bottom of your program, and can not be defined within another [[function|Function]], [[Subroutine|Subroutine]] or control block ([[ifthen|If/Then]], [[dountil|Do/Until]], ...)

==== Example ====

<code>
# 100 random circles
clg
for x = 1 to 100
   call draw()
next x
end

function rnd(n)
   rnd = int(rand*n)
end function

subroutine draw()
   color rnd(256),rnd(256),rnd(256)
   circle rnd(graphwidth), rnd(graphheight), rnd(graphwidth/10)
end subroutine
</code>
draws\\
{{:en:subroutine_circle.png|Circles}}
==== See Also ====
{{page>en:start#Program Control&noheader}}

==== New To Version ==== 
0.9.9.1