SET

In this section:

The SET call-back takes two arguments each of type INTEGER. When the call-back is called, the first argument is set to the value of the second at the time when winio@ is called. SET returns the value 1 so that any necessary updates take place. Here is an example.

WINAPP
INTEGER v,w,winio@,x,ctrl
v=0
x=1
w=winio@('%`cn%^tt[Set]&','SET',v,x)
w=winio@('%2nl%4rd&',v)
w=winio@('%lw',ctrl)
x=2
END

The variable v is initially zero and takes the value 1 (rather than 2) when the button is clicked. The SETF callback performs the same operation on floating-point numbers.